Type forwarding is a CLR feature that allows us to move a type from its original assembly to another assembly in such a way that there is no need to recompile the applications referring to the original assembly.
The Requirement
Suppose you have created an assembly named
MyLibrary which contains a class named MyClass. Let's say, some of your applications refer to the MyLibrary whih contains MyClass. In a later phase, you decide to move MyClass from MyLibrary to a newly created assembly called MyAdvancedLibrary. If you ship a new version of MyLibrary (which now doesn't have MyClass), along with MyAdvancedLibrary, then your existing applications looking for MyClass in MyLibrary and end up with errors. The Solution
Now, in order to run your applications without recompiling them, you can use the Type Forwarding feature of the Common Language Runtime.
In the above scenario, you need to apply
TypeForwardedToAttribute to the new version of your MyLibrary, so that requests for MyClass are now forwarded to the newly created library MyAdvancedLibrary that now contains MyClass.Steps
- Move the
MyClasscode fromMyLibrarytoMyAdvancedLibrary. - Put
TypeForwardedToAtrributeinMyLibraryfor theMyClasstype. - Compile the newly created
MyAdvancedLibrary. - Add a reference of
MyAdvancedLibraryintoMyLibrary. - Recompile
MyLibrary(becauseMyClassused to be located in that).
// C# Example
[assembly:TypeForwardedToAttribute(typeof(MyClass))] Now, you can ship the new version of
MyLibrary along with MyAdvancedLibrary and run your applications without a recompile!The Limitation
The .NET Framework version 2.0 does not allow type forwarding from assemblies written in Visual Basic. However, a Visual Basic application can consume forwarded types if it uses the assemblies coded in C# or C++.
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