Call ambiguous between methods that return different types when the return type is explicit

Question

Possible Duplicate:
Question about ambiguous calls in C#

I have these two methods:

TypeA MyMethod(string s) {}
TypeB MyMethod(string s) {}

The following call gives me "ambiguity between methods" error:

TypeA ta = MyMethod("some string");

How does this happen when I'm asking for a TypeA object to return explicitly and not via var or otherwise?

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TypeA and TypeB are separate classes, they don't have anything in common.

Answer 1

From the C# spec v4.0, section 1.6.6:

The signature of a method must be unique in the class in which the method is declared. The signature of a method consists of the name of the method, the number of type parameters and the number, modifiers, and types of its parameters. The signature of a method does not include the return type.

You have two methods with the same signature because they differ only in the return type. This is not allowed.