Technical Weblog of Eric Charran : WCF Development

“Create Unit Tests” Screen Shows No Types in Visual Studio 2008 SP1

echarran — Sat, 14 Nov 2009 02:13:14 GMT

When trying to create a unit test in a test project, the “Create Unit Tests” screen shows no types, thus the wizard cannot continue. The [OK] button is disabled, and the only thing the user can do is cancel the unit test wizard. This happens on Visual Studio 2008 SP1 on x64 (for me).

Not sure why this is, but if you have a database project type [SQL Server 2005/2008], remove that project from the solution and the type window for the unit test wizard will now work and let you browse types in your project for test method creation.

HOWTO: Properly Utilize a WCF Service Proxy Class in Code

echarran — Thu, 22 May 2008 20:32:01 GMT

One critical thing when using proxy classes is to be aware of how to properly call methods and then close the proxy. Because the proxy makes HTTP requests, (assuming your service is housed within IIS), unless you call .Close() on the proxy, those requests will be held open in IIS and threads will remain dedicated to them. Thus, without closing your proxy, you will soon have sopped up IIS resources with repeated calls to the service from your application. Eventually, you will see an error with text similar to the following:

"TimeoutException was Unhandled"

The request channel timed out while waiting for a reply after <Insert Time Interval Here>

The best practice is to call .Close() on your service proxy after each call. Call it in a finally block and ensure to check to see if the state on the proxy is .Opened first.

Wallpaper Manager 1.0 Update

echarran — Tue, 18 Dec 2007 21:33:17 GMT

Hi all,

I've updated the Wallpaper Manager written in WCF to the 3.5 version of the Framework. I have also included some bug fixes and eliminated some exceptions when the program can't find a directory, or there are no items in a specified directory. Below is the original post and the link to download still works, but its the updated bits. Also, you have to uninstall the previous version and install the new one.

Vision and Purpose

The Wallpaper Manager is a Proof of Concept WPF application I built using Expression Blend and Visual Studio .NET 2008 (Codename Orcas). The application exists as a Windows Presentation Foundation XAML form application that is designed to provide users with the ability to control their desktop wallpaper by cascading over specified directories and allowing users to quickly browse, change and establish timed transitions between wallpaper.

Get it here from my Windows Live SkyDrive:

Here are some usage notes and information below. Also note that you will be prompted to install the .NET framework Beta 3.5. There is a feature of the .NET Framework 3.5 beta that will allow it to get updates as newer and finally RTM bits are released.

User Interface

Wallpaper Manager Main Form
1. The main form is where users configure settings, navigate image collections, specify directories, start and stop the timer, save settings and exit the application

Wallpaper Manager Mini
1. Wallpaper Manager Mini is a task tray icon activated mini-browser that allows for the navigation through the image collection, setting of selected wallpaper and the ability to restore the main Wallpaper Manager window

Features

Browse a directory of images (including subdirectories if optioned by the user) for wallpaper
1. Users can browse through a directory and its subdirectories for images with Wallpaper Manager and set the desktop wallpaper to a specific image
2. Users can specify whether or not to cascade into subdirectories for images
3. Users can use the image navigation buttons to navigate forward and backward through discovered images and set the image as the desktop background

Time desktop wallpaper transitions
1. Users can specify a directory (including subdirectories) for source images that will be rotated through on a specified frequency
2. Once the specified rotation frequency has passed, Wallpaper Manager will set the desktop background to the next sequential image
3. If there are no more sequential images, Wallpaper Manager will loop through the image collection and go back to the first image in the specified directory (at its highest level if subdirectories are included)

Event Notifications
1. Wallpaper Manager will allow users to receive Balloon Tip feedback of specific events under the following circumstances (if so optioned on the main form)
  1. Wallpaper Image Changes
  2. Minimize to Tray on Close
  3. Saving of Settings
  4. Start and Stop of Wallpaper Timer

Wallpaper Manager Mini
1. Wallpaper Manager (if set to minimize to the tray on close) will provide users with a mini-browser interface so that users can quickly rotate through a collection of images and set wallpaper
2. By clicking on the task tray icon for Wallpaper Manager, the mini-browser will render the next wallpaper to be rendered in the collection as well as image navigation buttons
3. Users can set the desired wallpaper from the mini-browser or choose to restore to the larger main form to adjust timer settings and other application settings

AutoResume Timer
1. Wallpaper Manager can be set to AutoResume wallpaper time settings on restart, including picking up with the last set wallpaper in the collection(if it still exists)
2. When Wallpaper Manager is set to AutoResume, it will open minimized to the task tray and then open the mini-browser as well as message the user that the timer has started according to the established rotation frequency

Known Issues

UNC Paths appear to upset the application. I'm looking into this
If you need to upgrade the application, after install, make sure that the WallpaperSettings settings XML file is completely removed or you might experience some strange behavior
1. This is only an issue if the version of Wallpaper Manager changes and not so much on a reinstall of the same version

There have been some instances where I experienced the timer settings not working correctly and that the timer function has been escalated. I'm looking into this
In order for timer changes to take place, Save Settings first

How to Arrange a Solution using the WCF Service Library and WCF Service Application Templates

echarran — Wed, 19 Sep 2007 04:19:51 GMT

In Visual Studio 2008 (Beta 2), there are two WCF application templates.

The WCF Service Library is a class library that defines a WCF service, that can be exposed through a variety of WCF hosting options (i.e., IIS, a custom built WCF host, or a Windows Service). This WCF class library defines the service, operation and data contracts and implements the service specification. The WCF class library also contains a app.config file which also has the settings that any host would need to expose the services endpoints, behaviors, etc. In fact, if you set the WCF class library as a start up project in Visual Studio 2008, it will host the service in a web application and launch the WCF Test Client (part of VS 2008) to allow inspection and test execution of the WCF class library's methods.

The WCF Service Application is a template that assumes you are building a service that will only be hosted within IIS. Thus, it defines the service, equips the project with a web.config and places the details about the endpoints, behaviors, etc. in that file. When set as a startup project, it will host the service in the development web server and listen for calls.

Observing the differences between these two templates is important because it might have ramifications on how WCF applications are developed. If you want to have your WCF application code hosted in eventually multiple hosts (i.e., IIS, custom built or Windows Service) the best approach is to place your service definition and implementation in a WCF class library. If your service will only ever need to be exposed as an IIS service (i.e., if its a front-end service wrapping some business logic/functionality that you exposed to external business trading partners via the Internet), then baking the code into the host like the WCF Service Application template does makes sense. In fact, at a later date, you can migrate the code into a WCF class library and "hallow out" the IIS host by point it to the library.

The trick I recently did is to place my service implementation in a WCF class library template, but expose it to a consuming application in the same solution. When adding a service reference to a WCF client, Visual Studio 2008 allows you to automatically discover services within the same solution. However, because a WCF class library has no host, it isn't visible as a service that can be added to a client. What is required is a host for the WCF class library.

To allow the WCF client to see the WCF class library as a service, I added a WCF Service Application project template to the solution and followed these steps:

Add a project reference to the WCF class library project
Rename the Service1.svc file to the service name of my choice
Deleted the Service1.svc.cs code behind file as we won't have any WCF Service implementation in this project
Viewed the markup of the Service1.svc file and altered it accordingly to refer to the types referenced from the WCF class library
<@ServiceHost Language="C#" Debug="true" Service="ProjectName.Service.Library.ProjectNameService"%>
<@Assembly Name="ProjectName.Service.Library" %>
Note that Service is the namespace of the referenced WCF class library dll and that the assembly is the name of the referenced assembly
Altered the web.config, replacing any mention of Service1 with the correct service name from the referenced assembly.
1. Note that an approach to this is to compare the web.config with the app.config of the WCF class library to make sure the service name and behavior between the files are equal
Build the WCF Service Application and test the wsdl by visiting the Service1.svc file and clicking on the wsdl link
Right click your WCF Client application project file in Visual Studio (in my case a Windows Forms project) and select Add Service Reference
Click the discover button and select to discover services within the solution
Assign the service a proper namespace

At this point, you should have a separate WCF class library that can be hosted anywhere (i.e., Windows Service, IIS, or custom-built host) and that can be debugged and tested by the built in WCF Service test harness. You also should have a wrapping IIS host for the WCF Service that can be discovered by potential WCF Service clients in the solution.

Exposing LINQ Generated Classes through WCF

echarran — Thu, 06 Sep 2007 01:42:36 GMT

The lure of using LINQ to generate classes and expose them as data contracts through WCF is extremely attractive. The designer-driven LINQ to SQL interface allows for generation of LINQ classes based on database objects (i.e., tables and stored procedures). The power here is that if any of those elements change, generation of the classes to accommodate those changes are easy and maintainable.

However, combining LINQ and WCF before Orcas was daunting because the LINQ classes were generated code. Any decoration of the methods there (required by WCF in order to make the LINQ classes data contracts) would easily be overwritten because the dbml designer would overwrite the accompanying .cs file which contained the definition of the LINQ classes. With Orcas Beta 2 there is a Serialize Mode property on the dbml design space that allows for the automatic decoration of the LINQ classes for WCF exposure.

Now you can automatically decorate your LINQ classes for WCF and specify namespaces for them without writing code and all through the LINQ to SQL designer. Simply focus the designer (don't select any classes) and examine its property sheet as below. Serialization Mode is normally not set. By specifying a serialization mode, all of the code receives the corresponding DataContract and DataMember attributes.

WCF Test Client: Failed Adding Service

echarran — Thu, 06 Sep 2007 01:36:00 GMT

When writing your first WCF service in Orcas Beta 2, you might set the service as a start up project and attempt to debug it. The challenge you will face is that the service will start and the WCF Test Client will launch and try to add the service. The problem that you will encounter may be as follows:

svcutil.exe has encountered a problem and needs to close....

WCF Test Client: Failed adding service./
Unhandled Exception: System.IO.FileLoadException: Could not load file or assembly 'svcutil, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. Strong name validation failed. (Exception from HRESULT: 0x8013141A)
File name: 'svcutil, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' ---> System.Security.SecurityException: Strong name validation failed. (Exception from HRESULT: 0x8013141A)
The Zone of the assembly that failed was:
MyComputer

The workaround is as follows in the forum post:

http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=1932994&SiteID=1

This is a known issue in Beta2. Svcutil.exe is not signed correctly.

1. Open the VS command prompt.

2. Browse to the bin directory of the windows SDK

3. Type: sn –Vr svcutil.exe

You only need to do this once. The test client will work.