How do you explain type forwarding in simple terms?

Question

I am preparing for MCTS 70-536, after reading this article. I am not 100% sure I understand the concept of typeforwarding. I find the steps given in the article even more confusing. Whats the deal if I am copying the sourcecode of type to be forwarded and recompiling it. What happens with old dll and the client ??

Answer 1

Type forwarding allows you to relocate a type between assemblies. So originally it is TypeA in AssemblyA. By applying type-forwarding, you can end with TypeA in AssemblyB.

The subtlety is the code that is already compiled doesn't see the change - they ask for the type in AssemblyA, and the runtime silently gives them the type from AssemblyB. This is very important if you have existing code.

However; new code cannot be recompiled referencing TypeA without you referencing AssemblyB.

So:

• old clients don't need to be recompiled
• however, you do need to rebuild both AssemblyA and AssemblyB in the above example
• new code (or any recompiled code) must now reference AssemblyB (the new one)