Graham Elliott

Integrating WCF and WF

One of the minor hurdles I came across when building out the first version of the über demo was how to call a Windows Communication Foundation (WCF) Service from a Windows Workflow Foundation workflow (WF).

The reason that this is more of a hurdle then you might expect is that Workflow Foundation does not have any "native" support for calling/invoking a WCF service... Well, not really, anyhow.

Basic(Http) Integration

WF does allow you to invoke a ASMX Web Service by using the InvokeWebService activity (see piccy below). This brings up the standard Visual Studio "Add Web Reference Interface", generates a client side proxy, and exposes a bunch of strongly bound properties for choosing the MethodName,  Parameters, ReturnValue etc.

Because you can call a standard ASMX web service, you can use the same method to invoke a WCF service that is exposed via a BasicHttpBinding endpoint. In the case of the AdentureWorks solution, I am calling the GetProducts service ...or more precisely, I am calling the following BasicHttpBinding endpoint:

<endpoint
    name="basicHttp"
     address=""
     binding="basicHttpBinding"
    contract="AdventureWorks.IProductsDB"/>

For this to work, I also had to configure the service to publish service metadata for retrieval using an HTTP/GET request.  

Slightly More Useful (but quick and dirty :-) Integration

So... Its pretty easy to call a WCF service from a workflow if you are happy to stick with a basic HTTP binding. But what if you want to use the full gamut of WCF features and bindings in your services?

If you take a look at the workflow in the AdventureWorks solution (piccy below) you will notice that I am using the InvokeWebService activity to call the GetProducts service and then using a code activity to to invoke the GetMostPopularProductsOfWeek service (using whatever binding I configure in the workflow host's app.config).

 The code for codeActivity1 looks like:

private void CodeActivity1_Execute(object sender, EventArgs e)
{
      //TODO: Add sensible robustness stuff here
      this.TopProducts = proxy.GetMostPopularProductsOfWeek();
}

All I am doing is calling a method on the WCF "proxy" that I pass to the workflow via custom property that looks like:

private IProductsDB proxy;

public IProductsDB Proxy
{
      get { return proxy; }
      set { proxy = value; }
}

This workflow property is populated by the workflow host, which in the case of the AdventrueWorks solution is the WPF Client, just before the workflow is kicked-off:

void GetProductList_OnClick(object sender, RoutedEventArgs e)
{
    if (SubCatID.Text != null)
    {
        // Construct workflow parameters
        Dictionary<string, object> properties = new Dictionary<string, object>();
        properties.Add("SubCatID", Int32.Parse(SubCatID.Text));

        properties.Add("Proxy", pdb);     <---- HERE

        // Start the workflow
        workflowInstance = workflowRuntime.CreateWorkflow(typeof(WorkflowLibrary1.Workflow1), properties);
        workflowInstance.Start();
    }
}