It has come to our attention that there has been some confusion over the mention of EWS.dll in the SDK documentation and Intellisense file. Where can people find it? Actually, you get to generate it. The Exchange 2007 SDK describes how to generate proxy classes by using the Add Web Reference. This may be fine for some of you, but others may want more flexibility with their proxy classes. This is where wsdl.exe comes into the picture. 

Wsdl.exe parses schema and WSDL files to generate Microsoft .NET code files. These code files contain the types that act as proxies for the serialization and deserialization of the XML messages that are sent to and from the Exchange server. Wsdl.exe is included in the .NET Framework SDK and with Visual Studio 2003 and 2005. Different proxy generators create different object models; in this discussion, I will focus on wsdl.exe version 2.0.50727.42, the version that is included with Visual Studio 2005.

Instead of using wsdl.exe, you can use the Add Web References option in Visual Studio 2005 to create proxy classes. (This option will still be available in Visual Studio 2008, except that it will be well hidden). I prefer to use wsdl.exe to generate my proxy classes, for two reasons: 1) I can easily extend the proxy classes to make them easier to use, and 2) I can reuse my compiled DLL in all my Exchange Web Services projects. If I use the Add Web References option in Visual Studio, I have to regenerate the proxy classes for each project and therefore I lose any modifications that I made to the autogenerated classes. Oh, and remember that changes made to autogenerated classes are not supported by Microsoft; you are on your own with those modifications.

Let's start by finding wsdl.exe. By default, the Windows SDK installs it to C:\Program Files\Microsoft SDKs\Windows\v6.0\Bin\wsdl.exe. You can also access wsdl.exe by using the Visual Studio 2005 Command Prompt. To find the Visual Studio 2005 Command Prompt, from the Start Menu, choose All Programs | Microsoft Visual Studio 2005 | Visual Studio Tools | Visual Studio 2005 Command Prompt. Wsdl.exe has been added to the Path environment variable of the Visual Studio 2005 Command Prompt so that you can access it easily.

Now that you know where to find wsdl.exe, you can learn more about it by reading the Web Services Description Language Tool (Wsdl.exe) topic.

You are now ready to generate the proxy classes. I like to use the Visual Studio 2005 Command Prompt to access wsdl.exe as it also has the C# compiler in the path. We will use the C# compiler in a bit. In the Visual Studio 2005 Command Prompt, I use the following parameters to generate my proxy classes:

wsdl /language:cs /out:EWS.cs /namespace:ExchangeWebServices

I chose C# as the output language type for my proxy classes. You can also use Visual Basic .NET or C++ proxy classes. EWS.cs is the output code file for my proxy classes. I used ExchangeWebServices for the name of the namespace that holds all the proxy types; this is consistent with the namespace that is used in the Exchange 2007 SDK documentation and the Intellisense files that are included in the downloadable SDK. The last argument is the URL to my Exchange Web Services endpoint.

So now you have a code file with the autogenerated proxies. Next, you compile your code file into an assembly for use in your Exchange Web Services projects. The C# compiler is available with the Visual Studio 2005 Command Prompt. Assuming that you named your code file EWS.cs, you can run the following command at the command prompt to compile your code into an assembly:

csc /target:library /out:EWS.dll EWS.cs

Notice that EWS.dll is the name of the compiled assembly. This is how EWS.dll is created.

Voila! Now you have an assembly that can be reused in all your Exchange Web Service projects. If you currently use the Add Web References option in Visual Studio 2005, I recommend that you start using wsdl.exe instead to generate your Exchange Web Services proxy classes.