Stephen Kaufman's WebLog : WCF

AppFabric and BizTalk

skaufman — Tue, 24 Nov 2009 05:37:00 GMT

There have been lots of questions lately about AppFabric (code named Dublin). These questions have centered around why Microsoft needs another middle tier solution and will AppFabric replace BizTalk.

Lets take a look at these questions as well as two additional questions; What is AppFabric and why does Microsoft need another middle tier solution? First, AppFabric is a distributed application server. To answer the other questions, we need to go in a little more depth.

Before .NET was released, developers working with the Microsoft technologies used COM+ to host their middle tier objects. Back then, when we needed to scale out our object oriented and object based applications we created middle tier code libraries and ‘hosted’ them in COM+. The COM+ host provided instance management (just-in-time activation), role-based security, automated transaction management as well as better memory and processor management, distributed transactions and a number of other services.

When .NET was introduced, we moved away from COM components and also moved away from using COM+ as a hosting model. This left a vacuum that so far had gone unfilled.

In attempts to fill this vacuum, individual developers had to create their own hosts. These hosts typically were Windows Services. However, these services usually didn’t include multi threading, scale out capabilities, tracking, monitoring, etc. – the types of functionality that has been in BizTalk for years. As Microsoft looked at BizTalk, as well as the .NET Framework, it was determined that there are many great features in BizTalk that if a scaled down version was available it would address gaps in the framework. Thus AppFabric was born.

For .NET developers writing applications using WCF and WF, AppFabric will fill the middle tier hosting vacuum. AppFabric will provide the host and will provide scalability and support for building out your middle tier application components. It also will simplify deployment, configuration, management and scalability of composite applications. The goal of AppFabric is to provide a server infrastructure, on which business logic developed in WF can be executed and exposed via WCF endpoints, without the need to design, develop, and support the infrastructural code.

The next question I hear is will AppFabric replace BizTalk? The answer is very clearly no.

AppFabric should be used when your architecture calls for an application level code-first object based approach. This is the same approach that is used by WF and WCF programming models and is the one that can be hosted in AppFabric and the additional functionality that AppFabric provides. AppFabric will provide a number of management and scalability features through IIS and WAS to provide the server infrastructure without the need to write the plumbing as you did before. This is a different approach than that of the XML Schema first approach that is used in BizTalk.

Use BizTalk when your architecture calls for an enterprise level message based approach. Use BizTalk when you need to isolate disparate systems that need to be connected. In point-to-point integrations, changes made to the provider system can have a profound impact on the consuming application. BizTalk natively provides a hub-based integration model which eases this burden and allows organizations to provide business services that are isolated from the impact of changes made to the systems and processes on which these services are based. This is achieved through the use of separate schemas, and the associated ability to easily develop message transformation logic using BizTalk’s Mapper tool. Use BizTalk if you have business-to-business requirements and need to integrate using technologies such as EDI, SWIFT, RosettaNet, AS2 or HL7.

The reality is that businesses will utilize both of these technologies in their different application architectures. This is not an either or decision but instead a decision of where and when to use each.

Keep in mind, however, that many of the same terms are used to describe the functionality provided with both BizTalk and AppFabric. These terms are things like Content Based Routing, Correlation, long running transactions, etc. Although the terms are the same the implementation and functionality is different. With all decisions, make sure that you take a couple of minutes to look under the hood and ensure that you understand the differences.

Follow Up from TechEd Europe

skaufman — Sat, 21 Nov 2009 05:46:00 GMT

Paolo Salvatori and I delivered a session titled 'Customizing and Extending the BizTalk WCF Adapters' and Paolo has created a number of fantastic blog entries around this subject. His latest entry goes through much of the content that was delivered in the session and he has included a number of links at the bottom for more WCF Adapter information and samples.

WCF: Did you know?

skaufman — Thu, 13 Aug 2009 01:15:00 GMT

Did you know that when doing contract first development and utilize a Boolean data type with a default value (lets just say the default value was set to true), WCF will not serialize out the default value in the message. WCF will only serialize out the value if it differs from the default.

This was an interesting scenario in BizTalk when we were trying to test for the Boolean to be true and we saw that it was actually empty.

Sometimes I wonder with these types of issues if I am the only one in the world that didn't know that. I am going to make the assumption that this will be news to more people then just me.

WSE, DIME; WCF, MTOM; OH My!

skaufman — Mon, 20 Jul 2009 20:51:00 GMT

I was recently working on a proof of concept where we needed to interface to a repository that returned the documents using DIME attachments. I don't know if you have had the 'opportunity' to work with DIME attachments before but there isn't much that still supports that format. Since the manufacturer of the repository wasn't upgrading their software to take advantage of the new MTOM format we needed to consume the DIME attachments and convert them to MTOM attachments through an exposed WCF end point.

My client was putting this service on their ESB, which was built using BizTalk, and we utilized the WSE 2.0 extensions (yes, you can still download them) for the DIME support.

To do this we downloaded the WSE extensions and created a class that we would call from within our Orchestration. We added a Web Reference to point to the web service of the repository. We then replaced the default inherited class in the proxy with the WSE class, Microsoft.Web.Services2.WebServicesClientProtocol. At this point we were ready to start writing code to consume the attachments.

In the code below, we loop through the attachments in the ResponseSoapContext and then load them into a stream object. We then used the Convert class to convert the byte array to the properly converted Base64String and placed that as the value of the Attachment node. The schema node's data type in the schema in BizTalk for the attachment is set to Base64Binary. The best part about this whole POC is that by putting our attachment in the Base64Binary data type, all that we need to do is set the encoding on the WCF adapter to MTOM and BizTalk will do all the MTOM work for us. Also in the code below, you will notice that we used Linq to XML. The great part of POC's is that you can play with the new technology and in this case see just how easy it is to put together the XML message. Even though we were playing with Linq, I still needed to pass back an XML Document for the Orchestration to consume.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Drawing;
using System.Xml.Linq;
using Microsoft.Web.Services2.Dime;
using System.IO;
using System.Xml.Serialization;
using System.Xml;

namespace OrchestrationHelper
{
    [Serializable]
    public class OrchestrationHelperWrapper
    {
        MyService.Service svc = new MyService.Service();

        public XmlDocument RetrieveAttachment(int token, string name)
        {
            XElement xmlTree = null;

            int iResult = svc.RetrieveFile(token, name);
            XElement myNode;

           if (iResult == 0) //0 = successful retrieve
                {
                    if (svc.ResponseSoapContext.Attachments.Count > 0)
                    {
                        XNamespace ns = "http://POC.DimeReturnSchema";
                        xmlTree = new XElement(ns + "ReturnedAttachments");
                        XElement xmlAttachments = new XElement("Attachments");
                        xmlTree.Add(xmlAttachments);
                        for (int index = 0; index < svc.ResponseSoapContext.Attachments.Count; index++)
                        {
                            Stream myStream = svc.ResponseSoapContext.Attachments[index].Stream;
                            int length = (int)myStream.Length;

                            byte[] bytes = new byte[length];
                            myStream.Read(bytes, 0, length);

                            myNode = new XElement("Attachment", Convert.ToBase64String(bytes));
                            xmlAttachments.Add(myNode);
                        }
                    }
                }

                XmlDocument xdoc = new XmlDocument();
                xdoc.LoadXml(xmlTree.ToString());

                return xdoc;
        }
    }
}

Back in BizTalk, in our Orchestration, we called the OrchestrationHelper through the ConstructMessage shape and assigned the returned Xml Document to the Orchestration Message. We created a WCF endpoint and selected Mtom encoding on the Binding tab of the WCF Transport Properties dialog.

The best part is that BizTalk automatically encoded anything that was set to Base64Binary to the MTOM format and it can all be done through configuration in the WCF adapter settings. All that we needed to do was to consume the DIME attachment and place it in an element with the right data type.

Exposing Custom WCF Headers through WCF Behaviors - Part 3

skaufman — Thu, 25 Jun 2009 03:51:00 GMT

In part 1, I covered how to create a custom behavior to inject headers into the dynamically created WSDL. In part 2, I showed how to either promote or write the header data to the BizTalk context.

What happens if I want different headers for different end points? What if I don't want to create a custom header component for each end point? What if I want to set, through configuration, weather I want to promote or write to the context? What if I want to add a new header item without the need to recompile?

In this part of the series we will look at the ability to create a behavior that exposes the properties through configuration to let you dynamically, per end point, set the header items. The configuration is not through a configuration file but instead will hook into the end point behavior dialog box that appears in the adapter configuration in BizTalk.

The finished configuration will look like this:

Let's start looking at code.

First we are going to look at a new class file that will represent the data that we need to set in the configuration section of the dialog box. The CustomHeader class is where much of the configuration dialog magic happens. The way you define the properties will define the way they appear in the configuration dialog box. If you define your property as a boolean or an enum then it will display as a drop down list box. If you define it as a class then you will get the ellipses.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Services.WCF.Behavior
{
    public class CustomHeader
    {
        public string Name { get; set; }

        public string Namespace { get; set; }

        public bool Required { get; set; }

        public ContextAction Action { get; set; }
    }
}

Where the ContextAction type is the enum listed below:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Services.WCF.Behavior
{
    public enum ContextAction
    {
        None = 0,
        Write = 1,
        Promote = 2
    }
}

The CustomHeader class is accessed and 'bound' to the dialog box through the CustomHeaderEndpointBehavior class. This class is just a renamed and modified version of the SoapHeaderEndpointBehavior class we saw in the previous two articles.

using System;
using System.Collections.Generic;
using System.Text;
using System.ServiceModel.Description;
using System.ServiceModel.Configuration;
using System.Configuration;
using System.ServiceModel;

namespace Services.WCF.Behavior
{
    public class CustomHeaderEndpointBehavior : BehaviorExtensionElement, IEndpointBehavior
    {
        #region BehaviorExtensionElement Methods

        public override Type BehaviorType
        {
            get { return typeof(CustomHeaderEndpointBehavior); }
        }

        protected override object CreateBehavior()
        {
            return new CustomHeaderEndpointBehavior(this.Headers);
        }

        //Copies the content of the specified configuration element to this configuration element
        public override void CopyFrom(ServiceModelExtensionElement extFrom)
        {
            base.CopyFrom(extFrom);
            CustomHeaderEndpointBehavior element = extFrom as CustomHeaderEndpointBehavior;
            if (element != null)
            {
                Headers = element.Headers;
            }
        }

        //Both properties are returned as a collection.
        protected override ConfigurationPropertyCollection Properties
        {
            get
            {
                if (_properties == null)
                {
                    _properties = new ConfigurationPropertyCollection();

                    _properties.Add(new ConfigurationProperty("Headers", typeof(List<CustomHeader>), null,
                    new SerializationConverter(typeof(List<CustomHeader>)), null, ConfigurationPropertyOptions.None));
                    base["Headers"] = new List<CustomHeader>();
                }
                return _properties;
            }
        }

        #endregion

        #region IEndpointBehavior Members

        public void AddBindingParameters(ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
        {
            bindingParameters.Add(this);
        }

        public void ApplyClientBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.ClientRuntime clientRuntime)
        {
            //throw new NotImplementedException();
        }

        public void ApplyDispatchBehavior(ServiceEndpoint endpoint, System.ServiceModel.Dispatcher.EndpointDispatcher endpointDispatcher)
        {
            endpointDispatcher.DispatchRuntime.MessageInspectors.Add(new CustomHeaderMessageInspector());
        }

        public void Validate(ServiceEndpoint endpoint)
        {
            //throw new NotImplementedException();
        }

        #endregion

        #region Class properties
        [ConfigurationProperty("Headers")]
        public List<CustomHeader> Headers
        {
            get
            {
                return (List<CustomHeader>)base["Headers"];
            }
            set
            {
                base["Headers"] = value;
            }
        }

        #endregion

        #region Class Fields
        private ConfigurationPropertyCollection _properties;
        #endregion

        #region Constructors
        public CustomHeaderEndpointBehavior(List<CustomHeader> headers)
        {
            this.Headers = headers;
        }
        public CustomHeaderEndpointBehavior() : base()
        {}

        #endregion
    }
}

First you will notice that there is a number of new methods. The first is the CopyFrom method. This method is needed to copy the contents of the configuration data entered in the dialog box so that we can gain access to it within our class. We then override ConfigurationPropertyCollection since the header properties are returned as a collection. We will add the properties to our internal collection based on the List<CustomHeader> object. We also add the class to the AddBindingParamters method.

One thing to note when creating the configuration class (in our case the CustomHeader class) is that the default behavior of the Transport Properties dialog box and underlying code expects that all configuration information will be of type string. If you are using other types then you need to create your own type converter to convert to a string representation and back. I have the code for the type converter at the bottom of this post called SerializationConverter.

In the code above, in the CustomHeaderEndpointBehavior class, there were a couple of custom objects. The first one we will dig into is in the ApplyDispatchBehavior where we add a new CustomHeaderMessageInspector.

The class implementation for the CustomHeaderMessageInspector looks like:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel.Dispatcher;
using System.Diagnostics;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.Xml;

namespace Services.WCF.Behavior
{
    class CustomHeaderMessageInspector : IDispatchMessageInspector
    {
        #region IDispatchMessageInspector Members

        public object AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel, System.ServiceModel.InstanceContext instanceContext)
        {
            List<KeyValuePair<XmlQualifiedName, object>> writeProps = new List<KeyValuePair<XmlQualifiedName, object>>();
            List<KeyValuePair<XmlQualifiedName, object>> promoteProps = new List<KeyValuePair<XmlQualifiedName, object>>();
            string writeKey = "http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties/WriteToContext";
            string promoteKey = "http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties/Promote";

            CustomHeaderEndpointBehavior bhv = null;

            if (instanceContext.Host.Description.Endpoints.Find(channel.LocalAddress.Uri) != null)
                bhv = instanceContext.Host.Description.Endpoints.Find(channel.LocalAddress.Uri).Behaviors.Find<CustomHeaderEndpointBehavior>();

            if (bhv != null)
            {
                foreach (CustomHeader hdr in bhv.Headers)
                {
                    int headerPos = OperationContext.Current.IncomingMessageHeaders.FindHeader(hdr.Name, hdr.Namespace);

                    if (headerPos < 0)
                    {
                        if (hdr.Required)
                        {
                            //Fault Condition
                            throw new ArgumentNullException(hdr.Name, "Required soap header not found.");
                        }
                    }
                    else
                    {
                        if (hdr.Action != ContextAction.None)
                        {
                            // Get an XmlDictionaryReader to read the header content
                            XmlDictionaryReader reader = OperationContext.Current.IncomingMessageHeaders.GetReaderAtHeader(headerPos);
                            XmlDocument d = new XmlDocument();

                            d.LoadXml(reader.ReadOuterXml());
                            XmlQualifiedName PropName1 = new XmlQualifiedName(hdr.Name, hdr.Namespace);

                            if (hdr.Action == ContextAction.Write)
                            {
                                writeProps.Add(new KeyValuePair<XmlQualifiedName, object>(PropName1, d.DocumentElement.InnerText));
                            }
                            else if (hdr.Action == ContextAction.Promote)
                            {
                                promoteProps.Add(new KeyValuePair<XmlQualifiedName, object>(PropName1, d.DocumentElement.InnerText));
                            }
                        }
                    }
                }
            }
            else
            {
                //Debug.WriteLine("*****AfterReceiveRequest: No Behavior found of type CustomHeaderEndpointBehavior.*****");
            }

            if (writeProps.Count > 0)
            {
                request.Properties[writeKey] = writeProps;
            }

            if (promoteProps.Count > 0)
            {
                request.Properties[promoteKey] = promoteProps;
            }

            return null;
        }

        public void BeforeSendReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
        {
        }

        #endregion
    }
}

As we look at this code, in the AfterReceiveRequest method we have included both the writeProps and the promoteProps variables as well as both namespaces. We then look in the instanceContext.Host.Description.Endpoints collection to find, within the behaviors collection, our CustomerHeaderEndPointBehavior object. Then we loop through each of the headers that was setup through configuration and look for them in the message headers collection. Finally, check if the header was required and if we need to write or promote the values.

Lastly, here is the code that does our type conversion from the CustomHeader class to a string representation (in our case this will be XML).

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;
using System.Xml.Serialization;
using System.IO;
using System.Xml;
using System.Globalization;

namespace Services.WCF.Behavior
{
    public class SerializationConverter : TypeConverter
    {
        private Type _type;
        public SerializationConverter(Type type)
        {
            _type = type;
        }

        #region Helper Utilities

        private object Deserialize(object value)
        {
            if (_type == null) throw new ArgumentNullException("", "Serialization type was not set. Use the SerializationConvertor(Type) constructor.");
            return Deserialize(value, _type);
        }

        private object Deserialize(object value, Type destinationType)
        {
            StringReader strRdr = null;
            XmlReader xmlRdr = null;

            try
            {
                if (!(value is string))
                throw new ApplicationException("Expecting parameter 'value' to be of type string. 'Value' is of type " + value.GetType().ToString());

                XmlSerializer serializer = new XmlSerializer(destinationType);
                strRdr = new StringReader(value.ToString());
                xmlRdr = XmlReader.Create(strRdr);

                return serializer.Deserialize(xmlRdr);
            }
            finally
            {
                strRdr.Close();
                xmlRdr.Close();
            }
        }

        private object Serialize(object value)
        {
            StringWriter wtr = null;

            try
            {
                if (value == null)
                throw new ArgumentNullException("value");

                StringBuilder sb = new StringBuilder();
                XmlSerializer serializer = new XmlSerializer(value.GetType());
                wtr = new StringWriter(sb);
                serializer.Serialize(wtr, value);

                return sb.ToString();
            }
            finally
            {
                wtr.Close();
            }
        }

        #endregion

        #region Collection code.
        //Class to string
        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
        {
            if (value is string)
            {
                return Deserialize(value);
            }
            else if (value.GetType() == _type)
            {
                return Serialize(value);
            }
            else
            {
                string msg = (_type == null ? "Value is not of type System.string and no type was specified at construction." : "Value is not of type System.string or " + _type.ToString() + ".");
                throw new ApplicationException(msg);
            }
        }

        //String to class
        public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
        {
            if (value is string)
            {
                return Deserialize(value, destinationType);
            }
            else if (value.GetType() == _type)
            {
                return Serialize(value);
            }
            else
            {
                string msg = (_type == null ? "Value is not of type System.string and no type was specified at construction." : "Value is not of type System.string or " + _type.ToString() + ".");
                throw new ApplicationException(msg);
            }
        }
        #endregion
    }
}

At this point we have all the code that is part of our project. Once this is compiled, we need to add the assembly to the machine config and add it to the BizTalk WCF endpoint. The process to implement this remains the same as that described at the bottom of part 1 of this series.

As always, the code in this post and this series are for reference only and are provided as is. Now that we have that out of the way, I hope that these posts have been helpful and have shown how to deal with header values in the WCF stack and shown the ability to create a behavior that exposes the properties through configuration to let you dynamically, per end point, set the header items.

Exposing Custom WCF Headers through WCF Behaviors - Part 2

skaufman — Thu, 11 Jun 2009 07:03:00 GMT

In part 1 we covered how to create a custom behavior to inject header data into the dynamically created WSDL.

In this part we will look at consuming the header data passed in.

By default BizTalk will take any custom header it finds in the incoming WCF message and automatically map them to the Message Context.

If it were really this simple we wouldn't need this posting.

So, what is the issue. The issue is that when BizTalk maps the header to the context it posts an xml fragment. This fragment could certainly be used as is and parsed each time you need to use it but that gets tedious quickly and certainly doesn't do good things to the performance of your solution.

What we need is to be able to parse the key and value of the header data when the message is submitted to BizTalk so that it looks like all of the other context entries (a key and a value pair).

There are a number of options to enable you to do this including creating a pipeline component. We are not going to go that route. Instead, we are going to add code directly to our behavior. I want everything to be encapsulated inside the behavior so that if developers decide to use the behavior they don't have to also remember to place a pipeline in the mix. By having a separate pipeline component we are creating an error prone system that won't be caught until after deployment has occurred.

To promote or write to the context when the message arrives we will modify the AfterReceiveRequest method on the SoapHeaderMessageInspector class. This class was created in Part 1 of this series. If you go back and look at that method you will see that we originally implemented it by returning null.

First lets look at what is required to write or promote to the Message Context in code. MSDN has a sample of how this can be done which I put below.

const string PropertiesToPromoteKey="http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties/Promote";
const string PropertiesToWriteKey="http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties/WriteToContext";

XmlQualifiedName PropName1=new XmlQualifiedName("Destination", "http://tempuri.org/2007/sample-properties");
XmlQualifiedName PropName2=new XmlQualifiedName("Source", "http://tempuri.org/2007/sample-properties");

//Create a List of KeyValuePairs that indicate properties to be promoted to BizTalk message context. 
//A Property Schema must be deployed and string values have a limit of 256 characters
List<KeyValuePair<XmlQualifiedName, object>> promoteProps=new List<KeyValuePair<XmlQualifiedName, object>>();
promoteProps.Add(new KeyValuePair<XmlQualifiedName, object>(PropName1, "Property value"));
wcfMessage.Properties[PropertiesToPromoteKey]=promoteProps;

//Create a List of KeyValuePairs that indicate properties to be written to BizTalk message context
List<KeyValuePair<XmlQualifiedName, object>> writeProps=new List<KeyValuePair<XmlQualifiedName, object>>();
writeProps.Add(new KeyValuePair<XmlQualifiedName, object>(PropName2, "Property value"));
wcfMessage.Properties[PropertiesToWriteKey]=writeProps;

We are going to use this code but will format it a bit differently. As I said earlier we need to modify the AfterReceiveRequest method to incorporate this code.

Our method implementation will look like:

public object AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel, System.ServiceModel.InstanceContext instanceContext)
{
    List<KeyValuePair<XmlQualifiedName, object>> writeProps = new List<KeyValuePair<XmlQualifiedName, object>>();
    const string PropertiesToWriteKey = "http://schemas.microsoft.com/BizTalk/2006/01/Adapters/WCF-properties/WriteToContext";

    Int32 headerPosition = OperationContext.Current.IncomingMessageHeaders.FindHeader(SoapHeaderNames.SoapHeaderName, SoapHeaderNames.SoapHeaderNamespace);

    if (headerPosition < 0)
    {
        //Fault Condition
        throw new ArgumentNullException(SoapHeaderNames.SoapHeaderNamespace + "#" + SoapHeaderNames.SoapHeaderName, "SoapHeader not found.");
    }

    // Get an XmlDictionaryReader to read the header content
    XmlDictionaryReader reader = OperationContext.Current.IncomingMessageHeaders.GetReaderAtHeader(headerPosition);
    XmlDocument d = new XmlDocument();

    d.LoadXml(reader.ReadOuterXml());

    foreach (XmlNode node in d.DocumentElement.ChildNodes)
    {
        if ((node.Name.ToLower().Equals(SoapHeaderNames.AppName.ToLower()) || node.Name.ToLower().Equals(SoapHeaderNames.UserName.ToLower())) && String.IsNullOrEmpty(node.InnerText))
        {
            throw new ArgumentNullException(node.Name, "Header value cannot be null.");
        }

        XmlQualifiedName PropName1 = new XmlQualifiedName(node.Name, SoapHeaderNames.SoapHeaderNamespace);
        writeProps.Add(new KeyValuePair<XmlQualifiedName, object>(PropName1, node.InnerText));
    }

    if (writeProps.Count > 0)
    {
        request.Properties[PropertiesToWriteKey] = writeProps;
    }

    return null;
}

This code shows how we can select and read the header, and then loop through each element in the header and promote it.

In order to promote properties into the context you need to have a property schema. We took the SoapHeader.xsd that we created in Part 1 of this post and used that for our property schema.

When we take a look at the content of the incoming message after compiling and deploying our changes we can now see that our key name appears under the Name column and our value appears under the Value column of the Context dialog box. We no longer have an xml fragment and no longer have to deal with the need to parse the fragment each time we want to use it. Now that we have this data in the context we can utilize it in the same we would with any other data that appears in the context. The best part is that it was all done in one location, through one artifact, and won't require the developer to remember to utilize another artifact to make the solution work.

In the next post, we will cover the ability to create a behavior that exposes the properties through configuration to let you dynamically, per end point, set the header items as well as determine whether you want the values written or promoted dynamically as well.

Exposing Custom WCF Headers through WCF Behaviors

skaufman — Sat, 30 May 2009 00:28:00 GMT

Since the WCF Publishing Wizard in BizTalk does not support adding custom headers defined at the server, we need to programmatically modify what gets created by the wizard to add custom headers. However, from the client you have the option to pass in header values at will. If you are passing in headers generated at the client BizTalk will take them and map them to the context. However, they show up as an XML fragment and not as individual data items. It becomes annoying to constantly parse the fragment each and every time you want to get to the data.

What we are really interested in is the ability to expose the end point with the header values already defined, accept the header values from the client and either promote or write the values to the context and lastly, be able to create a behavior that you can attach to your WCF endpoint that exposes the properties through configuration to let you dynamically, per end point, set the header items and what you want to do with them as they are submitted. This will be a three part posting with a post covering each of these features.

For this first post, we will focus on the ability to expose the end point with the header values already defined. What makes this even more interesting is that there is no WSDL file as this gets generated dynamically when you access the SVC file. If you wish you can create a static WSDL file and then use the externalMetadataLocation attribute of the element in the Web.config file that the wizard generates to specify the location of the WSDL file. Then the static WSDL file will be sent to the user in response to WSDL and metadata exchange (MEX) requests instead of the auto-generated WSDL.

In our solution, we did not want to have to create WSDL files for each of our endpoints, nor did we want to maintain them. We needed a way to hook in to the dynamic WSDL creation process.

There are a number of posts out there that talk about this but after reviewing them I found that none of them gave the whole picture. They were all very good and they provided enough information to fill in many missing pieces but there was enough missing that I though it warranted looking at the whole picture.

We are going to start by creating our own EndPointBehavior. The EndPointBehavior allows us to inject custom functionality in the WCF execution pipeline.

To create the EndPointBehavior we need to create a solution that references System.ServiceModel.dll and includes a class that derives from BehaviorExtensionElement, IWsdlExportExtension and IEndpointBehavior. We need the functionality of the BehaviorExtensionElement to implement the configuration of the behavior, the functionality of the IWsdlExportExtension to change the generated WSDL and the functionality of the IEndPointBehavior to define the endpoint and its behavior.

Lets add a class file to our solution called SoapHeaderEndpointBehavior. After we create the class and inherit from our objects we need to add the following line of code to the ExportEndPoint method

SoapHeaderWsdlExport.ExportEndpoint(exporter,context);

and we need to add the following two lines of code to the ApplyDispatchBehavior method.

SoapHeaderMessageInspector headerInspector = new SoapHeaderMessageInspector();
endpointDispatcher.DispatchRuntime.MessageInspectors.Add(headerInspector);

Our code should look like this:

using System;
using System.Collections.Generic;
using System.Collections;
using System.Configuration;
using System.Runtime.Serialization;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.Configuration;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;
using System.Text;
using System.Xml;
using System.Xml.Schema;
using System.Web.Services;
using System.Web.Services.Description;
using WsdlDescription = System.Web.Services.Description.ServiceDescription;

namespace Services.WCF.ServiceBehavior
{
    public class SoapHeaderEndpointBehavior : BehaviorExtensionElement, IWsdlExportExtension, IEndpointBehavior
    {
        #region BehaviorExtensionElement Members

            public override Type BehaviorType
            {
                get
                {
                    return typeof(SoapHeaderEndpointBehavior);
                }
            }

            protected override object CreateBehavior()
            {
                return new SoapHeaderEndpointBehavior();
            }
        #endregion

        #region IWsdlExportExtension Members

            public void ExportContract(WsdlExporter exporter, WsdlContractConversionContext context)
            {
                //throw new NotImplementedException();
            }

            public void ExportEndpoint(WsdlExporter exporter, WsdlEndpointConversionContext context)
            {
                SoapHeaderWsdlExport.ExportEndpoint(exporter,context);
            }

        #endregion

        #region IEndpointBehavior Members

            public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
            {
                //throw new NotImplementedException();
            }

            public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
            {
                //throw new NotImplementedException();
            }

            public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
            {
                SoapHeaderMessageInspector headerInspector = new SoapHeaderMessageInspector();
                endpointDispatcher.DispatchRuntime.MessageInspectors.Add(headerInspector);
            }

            public void Validate(ServiceEndpoint endpoint)
            {
               //throw new NotImplementedException();
            }

        #endregion
    }
}

When we added code to the ExportEndpoint method, we utilized a custom object. Let's add another class to our solution to implement the SoapHeaderWsdlExport. This class will add a header schema and its namespace, create and add a header message description and finally add the header to the operation.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml.Schema;
using System.Reflection;
using System.Web.Services.Description;
using System.Xml;
using System.ServiceModel.Description;
using WsdlDescription = System.Web.Services.Description.ServiceDescription;

namespace Services.WCF.ServiceBehavior
{
    class SoapHeaderWsdlExport
    {
        public static void ExportEndpoint(WsdlExporter exporter, WsdlEndpointConversionContext context)
        {
            // Read the schema of the custom header message
            XmlSchema customSoapHeaderSchema = XmlSchema.Read(Assembly.GetExecutingAssembly().GetManifestResourceStream("Services.WCF.ServiceBehavior.SoapHeader.xsd"),
                new ValidationEventHandler (SoapHeaderWsdlExport.ValidationCallBack));

            // Create the HeaderMessage to add to wsdl:message AND to refer to from wsdl:operation
            System.Web.Services.Description.Message headerMessage = CreateHeaderMessage();

            foreach (WsdlDescription wsdl in exporter.GeneratedWsdlDocuments)
            {
                // Add the schema of the CustomSoapHeader to the types AND add the namespace to the list of namespaces
                wsdl.Types.Schemas.Add(customSoapHeaderSchema);
                wsdl.Namespaces.Add("sh", SoapHeaderNames.SoapHeaderNamespace);

                // The actual adding of the message to the list of messages
                wsdl.Messages.Add(headerMessage);
            }

            addHeaderToOperations(headerMessage, context);
        }

        private static System.Web.Services.Description.Message CreateHeaderMessage()
        {
            // Create Message
            System.Web.Services.Description.Message headerMessage = new System.Web.Services.Description.Message();

            // Set the name of the header message
            headerMessage.Name = SoapHeaderNames.SoapHeaderName;

            // Create the messagepart and add to the header message
            MessagePart part = new MessagePart();
            part.Name = "Header";
            part.Element = new XmlQualifiedName(SoapHeaderNames.SoapHeaderName, SoapHeaderNames.SoapHeaderNamespace);
            headerMessage.Parts.Add(part);

            return headerMessage;
        }

        private static void addHeaderToOperations(System.Web.Services.Description.Message headerMessage, WsdlEndpointConversionContext context)
        {
            // Create a XmlQualifiedName based on the header message, this will be used for binding the header message and the SoapHeaderBinding
            XmlQualifiedName header = new XmlQualifiedName(headerMessage.Name, headerMessage.ServiceDescription.TargetNamespace);

            foreach (OperationBinding operation in context.WsdlBinding.Operations)
            {
                // Add the SoapHeaderBinding to the MessageBinding
                ExportMessageHeaderBinding(operation.Input, context, header, false);
                ExportMessageHeaderBinding(operation.Output, context, header, false);
            }
        }

        private static void ExportMessageHeaderBinding(MessageBinding messageBinding, WsdlEndpointConversionContext context, XmlQualifiedName header, bool isEncoded)
        {
            // For brevity, assume Soap12HeaderBinding for Soap 1.2
            SoapHeaderBinding binding = new Soap12HeaderBinding();
            binding.Part = "Header";
            binding.Message = header;
            binding.Use = isEncoded ? SoapBindingUse.Encoded : SoapBindingUse.Literal;

            messageBinding.Extensions.Add(binding);
        }

        private static void ValidationCallBack(object sender, ValidationEventArgs args)
        {
            if (args.Severity == XmlSeverityType.Warning)
                Console.WriteLine("\tWarning: Matching schema not found. No validation occurred." + args.Message);
            else
                Console.WriteLine("\tValidation error: " + args.Message);

        }

    }
}

In the addHeaderToOperations method there are two calls to the ExportMessageHeaderBinding method. The second call passes the operation.Output parameter which will pass the header back to the calling application with the response message. This also also means that the method signature at the client will be to pass in the header object by Ref. Since we needed the client to pass the header data into BizTalk we didn't need to echo the header back to the client so we deleted this line. If you want to echo it back then keep this line (as shown in the code above).

Also, in the code above, in the ExportEndpoint and CreateHeaderMessage methods there was another custom class called SoapHeaderNames. This class contained the values that we wanted to place in the custom header. By creating a class for this data we could limit the location of this information to one location. The code for the SoapHeaderNames class looks like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Services.WCF.ServiceBehavior
{
    public static class SoapHeaderNames
    {
        public const String SoapHeaderName = "SoapHeader";

        public const String AppName = "App";
        public const String UserName = "User";

        public const String SoapHeaderNamespace = http://servicebehavior.mycompany.com;
    }
}

Way back at the top, in the ApplyDispatchBehavior method of the SoapHeaderEndpointBehavior class we have a custom object called SoapHeaderMessageInspector. Therefore, let's add another class for the SoapHeaderMessageInspector. There are two methods that we must implement on the IDispatchMessageInspector and they are the AfterReceiveRequest and the BeforeReceiveRequest. Since we are interested in applying the headers in the dynamic WSDL we will only need code in the BeforeReceiveRequest. The code will look like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel.Dispatcher;
using System.ServiceModel;
using System.Xml;

namespace Services.WCF.ServiceBehavior
{
    class SoapHeaderMessageInspector: IDispatchMessageInspector
    {

        #region IDispatchMessageInspector Members

            public object AfterReceiveRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel, System.ServiceModel.InstanceContext instanceContext)
            {
                return null;
            }

            public void BeforeSendReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
            {
                // Look for my custom header in the request
                Int32 headerPosition = OperationContext.Current.IncomingMessageHeaders.FindHeader(SoapHeaderNames.SoapHeaderName, SoapHeaderNames.SoapHeaderNamespace);

                // Get an XmlDictionaryReader to read the header content
                XmlDictionaryReader reader = OperationContext.Current.IncomingMessageHeaders.GetReaderAtHeader(headerPosition);

                // Read through its static method ReadHeader
                SoapHeader header = SoapHeader.ReadHeader(reader);

                if (header != null)
                {
                    // Add the header from the request
                    reply.Headers.Add(header);
                }
            }

        #endregion
    }
}

This code grabs the header section and will inject the header elements. In the BeforeSendReply method you will see we are using a SoapHeader object. This object contains the properties and methods to deal with the elements that we will be reading and writing to the header.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Xml;
using System.ServiceModel.Channels;

namespace Services.WCF.ServiceBehavior
{
    [Serializable]
    public class SoapHeader: MessageHeader
    {
        private string _app;
        private string _user;

        public string App
        {
            get
            {
                return (this._app);
            }
            set
            {
                this._app = value;
            }
        }

        public string User
        {
            get
            {
                return (this._user);
            }
            set
            {
                this._user = value;
            }
        }

        public SoapHeader()
        {
        }

        public SoapHeader(string app, string user)
        {
            this._app = app;
            this._user = user;
        }

        public override string Name
        {
            get { return (SoapHeaderNames.SoapHeaderName); }
        }

        public override string Namespace
        {
            get { return (SoapHeaderNames.SoapHeaderNamespace); }
        }

         protected override void OnWriteHeaderContents(System.Xml.XmlDictionaryWriter writer, MessageVersion messageVersion)
        {
            // Write the content of the header directly using the XmlDictionaryWriter
            writer.WriteElementString(SoapHeaderNames.AppName, this.App);
            writer.WriteElementString(SoapHeaderNames.UserName, this.User);
        }

        public static SoapHeader ReadHeader(XmlDictionaryReader reader)
        {
            String app = null;
            String user = null;

            // Read the header content (key) using the XmlDictionaryReader
            if (reader.ReadToDescendant(SoapHeaderNames.AppName, SoapHeaderNames.SoapHeaderNamespace))
            {
                app = reader.ReadElementString();
            }

            if (reader.ReadToDescendant(SoapHeaderNames.UserName, SoapHeaderNames.SoapHeaderNamespace))
            {
                user = reader.ReadElementString();
            }

            if (!String.IsNullOrEmpty(app) && !String.IsNullOrEmpty(user))
            {
                return new SoapHeader(app, user);
            }
            else
            {
                return null;
            }
        }

    }
}

There is also a schema, called SoapHeader.xsd, that needs to be added to the project as well. This schema defines the message contract for the header and is referenced and used in the ExportEndpoint method of the SoapHeaderWsdlExport class and looks like this:

<?xml version="1.0" encoding="utf-16"?>
<xs:schema xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:b="http://schemas.microsoft.com/BizTalk/2003" xmlns="http://servicebehavior.mycompany.com" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://servicebehavior.mycompany.com" xmlns:xs="http://www.w3.org/2001/XMLSchema">
    <xs:element name="SoapHeader">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="App" type="xs:string" />
                <xs:element name="User" type="xs:string" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

At this point we have all the code that is part of our project. Once this is compiled, we need to add the assembly to the machine config.

There is an easy way to add entries by using the SvcConfigEditor.exe tool. This tool is part of the Windows SDK and, if installed, can be found in the \Program Files\Microsoft SDKs\Windows\v6.0A\Bin directory.

Once this utility is open you can click on the File ->Open->Config File menu item. Open the machine.config file. At the bottom of the tree view on the left side you will see an Advanced folder. Expand that node and expand the the Extensions folder. Click on the the 'behavior element extensions' node. At the bottom right, click on the new button. This will bring up the Extension Configuration Element Editor dialog box. Enter the name you wish to give to your extension and then click on the ellipses next to type. This will bring up the Type Browser dialog box. Browse to your component (also note that you can select assemblies already placed in the GAC). Once selected, your fully qualified assembly name will be entered. Select Save under the File menu. You are now ready to start using the new behavior.

Up to this point everything we have done has been specifically WCF functionality. The next paragraph will outline how we can utilized this behavior in a BizTalk WCF endpoint.

Create a WCF endpoint in BizTalk (if you need more information on creating a WCF endpoint check out the docs on MSDN (Insert Link)). One thing to keep in mind is that when you create a WCF end point in BizTalk using one of the standard bindings you will not have the option to specify a behavior. In order to specify a behavior you need to specify either the WCF-Custom or WCF-CustomIsolated binding. Once you select the binding type, click on the Configure button and the Transport Properties dialog will appear. Select the Behavior tab and then right click on the the Endpoint Behavior node. Once the popup menu appears, select Add extension. Select your behavior from the Select Behavior Extensions dialog box and click OK. Enter the rest of the specific information you need for the end point and click OK to save your endpoint.

We have now done everything that is needed to create a custom behavior including the ability to link into the dynamic WSDL creation process at run time, register the behavior and finally to use the behavior.

Now, when you create a client against the end point you will see that there will be two parameters for the web method call. The first will be the custom header and the second will be the message body. When we look in the object browser for the header object we will see that the two items appear that we defined in our behavior.

As I said at the beginning of this post, this will be a three part series. What we have not covered is the ability to accept these header values from the client and promote or write the values to the context (part 2) and we have not covered the ability to create a behavior that exposes the properties through configuration to let you dynamically, per end point, set the header items (part 3).

More Information on Processing MSMQ Messages in FIFO Order

skaufman — Wed, 20 Aug 2008 20:52:00 GMT

In two of my previous posts I talked about processing MSMQ messages in FIFO order with WCF.

The way that WCF, along with the MSMQ binding, works there could be a couple of situations in which messages may actually not process in FIFO order.

The most prevalent is a rollback. When a message is rolled back the process is asynchronous and thus end up not only having that message take time to get back to the head of the queue but may also lead to messages being processed while the rolled back message is in flight.

However, not all is lost. By adding the changes below you can further ensure that you can make WCF behave like a pure System.Messaging coded system and still get your messages in FIFO order.

So, add

as an endpoint behavior and setting

ReleaseServiceInstanceOnTransactionComplete = false

on the Service Behavior (along with the InstanceContextMode and the ConcurrencyMode)

Processing multiple queues in FIFO order with WCF

skaufman — Thu, 21 Feb 2008 06:53:00 GMT

In my previous entry on Processing FIFO MSMQ Messages using WCF I said that I would cover processing multiple queues and processing each queue in FIFO order.

If you remember, our requirement was to processe messages we receive from a legacy system through MSMQ in FIFO order. Well we found that there were a couple of issues. Neither of them was a surprise - FIFO processing is slow and there is no scale out.

So, we did a little more investigation and we found that we could segment our processing by message types (each being sent through their own queue) and then process each in FIFO order. The FIFO processing is the same as in the past blog post. This blog entry is focused on dynamically adding and creating hosts for each of the queues.

We need a way to be able to add queue bindings in the .config file and have the application recognize the new queue without the need to modify code or have the application have any knowledge of how many queues would be monitored.

So, with this, I would set up the .config file looks like this:

<endpoint address="msmq.formatname:DIRECT=OS:.\private$\EventManagementQueueX"

binding="msmqIntegrationBinding"

bindingConfiguration="EventProcessorBinding"

behaviorConfiguration="BatchingBehavior"

contract="EventManagement.IMSMQEventInterface">

</endpoint>

</service>

<endpoint address="msmq.formatname:DIRECT=OS:.\private$\EventManagementQueueY"

binding="msmqIntegrationBinding"

bindingConfiguration="EventProcessorBinding"

behaviorConfiguration="BatchingBehavior"

contract="EventManagement.IMSMQEventInterface">

</endpoint>

</service>

</services>

The idea is to be able to add a new service entry for each new message type with a new endpoint address and have the code spin up a new service host. The code to make this happens looks like this:

public class EventProcessor

{

private List<ServiceHost> svcHosts = new List<ServiceHost>();

private MSMQEventService mqevtsvc;

public void ProcessMessages()

{

mqevtsvc = new MSMQEventService();

ServicesSection SvcSec = (ServicesSection)ConfigurationManager.GetSection("system.serviceModel/services");

string MSMQSvcName = mqevtsvc.GetType().FullName;

string baseName = ConfigurationManager.AppSettings["EventQueueName"];

Uri baseAddress = new Uri(baseName);

//Roll through the service entries and create service hosts to handle them

foreach (ServiceElement svc in SvcSec.Services)

{

if (svc.Name.StartsWith(MSMQSvcName))

{

object svcObj = null;

string Suffix = svc.Name.Substring(MSMQSvcName.Length);

if (Suffix == string.Empty)

{

svcObj = mqevtsvc;

}

else

{

svcObj = CreateMSMQObj(Suffix);

}

if (svcObj == null)

{

ErrorHandler.Instance.OnError("Error creating service type " + mqevtsvc.GetType().Name + Suffix, EventLogEntryType.Warning, ErrorHandler.WarningNumber.ServiceStarting);

}

else

{

ServiceHost newSvc = new ServiceHost(svcObj, baseAddress);

newSvc.Faulted += new EventHandler(serviceHost_Faulted);

svcHosts.Add(newSvc);

}

else

{

ErrorHandler.Instance.OnError(string.Format("Service name {0} must begin with {1}", svc.Name, MSMQSvcName), EventLogEntryType.Warning, ErrorHandler.WarningNumber.ServiceStarting);

}

// Open the ServiceHostBase to create listeners and start listening for messages.

foreach (ServiceHost svcHost in svcHosts)

{

svcHost.Open();

}

private object CreateMSMQObj(string SuffixName)

{

CSharpCodeProvider loCompiler = new CSharpCodeProvider();

CompilerParameters loParameters = new CompilerParameters();

loParameters.ReferencedAssemblies.Add("System.dll");

loParameters.ReferencedAssemblies.Add(this.GetType().Assembly.Location);

loParameters.ReferencedAssemblies.Add(typeof(ServiceHost).Assembly.Location);

loParameters.GenerateInMemory = true;

string Code = @"

using System;

using System.ServiceModel;

namespace EventManagement

{

public class MSMQEventService{0} : MSMQEventService, IMSMQEventInterface, IDisposable

{

}

Code = Code.Replace("{0}", SuffixName);

CompilerResults loCompiled = loCompiler.CompileAssemblyFromSource(loParameters, Code);

if (loCompiled.Errors.HasErrors)

{

//……add code here to process errors

}

Assembly loAssembly = loCompiled.CompiledAssembly;

object loObject = loAssembly.CreateInstance("EventManagement.MSMQEventService" + SuffixName);

return loObject;

}

There are two interesting parts to this code. The first is at the top where the .config file is read. The second is in the CreateMSMQObj private method.

When the .config file is read the service name attribute is read and that is used as part of the class name that is used with the ServiceHost.

During the CreateMSMQObj method, we are dynamically creating a class for each of the service elements from the .config file.

At this point we have a system that can dynamically read from multiple queues, defined at runtime, and process the messages in each queue in FIFO order.

This code is not the full source code and some of the processing code has been taken out for brevity. Hopefully, this will provide a glimpse and a provide a head start to process multiple queues in FIFO order.

MSMQ Label Property and WCF

skaufman — Tue, 18 Dec 2007 08:30:00 GMT

The label property of an MSMQ message has been used for many things. Developers still use the label property and want to continue to use it. So, how do you get access to this property in WCF before posting your message to the queue.

It turns out that if you are using the NetMSMQBinding you can't. After thinking about this a bit it makes sense since the NetMSMQBinding only uses MSMQ as an transport mechanism between two endpoints. In this case any data you want to send between these two endpoints needs to be in the message body. This is so your endpoints can be agnostic to the underlying transport and allow you to swap it out without having to modify your code.

To be able to utilize the label property you need to use the MsmqIntegrationBinding. The MsmqIntegrationBinding class enables WCF to use the types defined in the System.Messaging namespace. The label property is on the MsmqIntegrationMessageProperty class which can be used as follows:

MsmqIntegrationMessageProperty property = MsmqIntegrationMessageProperty.Get(message);

string lbl = property.Label

Processing FIFO MSMQ Messages using WCF

skaufman — Mon, 17 Sep 2007 03:33:00 GMT

I have been having fun working on the middle tier of an application which is using BizTalk, Windows Workflow, MSMQ and the Windows Communication Framework.

One of the requirements is to processes messages we receive from a legacy system through MSMQ in FIFO order.

We used WCF to communicate with MSMQ and used the msmqIntegrationBinding binding since the legacy application was placing the messages on the queue.

The FIFO processing seemed to be little more difficult to iron out. It turns out that by default a service's InstanceContextMode is PerSession. If the channel is a datagram then the IntanceContextMode degrades to PerCall. So what happens is that the WCF runtime will create a new service instance for each available request/message up to the MaxConcurrentCalls/MaxConcurrentInstance setting utilizing multiple threads. This was not going to provide my FIFO processing.

So, to set WCF to only pull and process one message at a time you need to set the service's InstanceContextMode to Single along with setting the ConcurrencyMode to single. The following code shows these settings:

[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single,

ConcurrencyMode = ConcurrencyMode.Single,

)]

public class MSMQEventService : IMSMQEventInterface, IDisposable

{

Once these settings are set you will achieve FIFO processing and WCF will only utilize a single thread and will process one message at a time from the single queue.

My next entry will cover processing multiple queues and processing each queue in FIFO order.