Method overloading return values [duplicate]

Question

In C# I need to be able to define a method but have it return one or two return types. The compiler gives me an error when I try to do it, but why isn't it smart enough to know which method I need to call?

int x = FunctionReturnsIntOrString();

Why would the compiler prevent me from having two functions with different return types?

Answer 1

From the last paragraph of section 1.6.6 of the C# 3.0 language specification:

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.

In IL two methods can differ by return type alone, but outside of reflection there is no means to call a method that differs only be return type.

Answer 2

While it may be obvious in this particular scenario, there are many scenarios where this is in fact not obvious. Lets take the following API for an example

class Bar { 
  public static int Foo();
  public static string Foo();
}

It's simply not possible for the compiler to know which Foo to call in the following scenarios

void Ambiguous() {
  Bar.Foo();
  object o = Bar.Foo();
  Dog d = (Dog)(Bar.Foo());
  var x = Bar.Foo();
  Console.WriteLine(Bar.Foo());
}

These are just a few quick samples. More contrived and evil problems surely exist.