CODEWITHSUNDEEP
c#visual-studio-2008c#-3.0extension-methods
imaximchuk
imaximchuk

Reputation: 748

Why is this call ambiguous?

Can anyone explain, why does the following code produce the error? (Compiling in Microsoft Visual Studio 2008)

class Base1 {  };
class Base2 {  }

interface I1   {   }
interface I2   {   }

class C : I1, I2 { }

static class Program
{

    static T M1<T>(this T t, I1 x) where T : Base1
    {
        return t;
    }

    static T M1<T>(this T t, I2 x) where T : Base2
    {
        return t;
    }

    static void Main(string[] args)
    {
        Base1 b1 = new Base1();
        C c = new C();
        b1.M1(c);
    }
}

the error is

The call is ambiguous between the following methods or properties: 'ConsoleApplication1.Program.M1<ConsoleApplication1.Base1>(ConsoleApplication1.Base1, ConsoleApplication1.I1)' and 'ConsoleApplication1.Program.M1<ConsoleApplication1.Base1>(ConsoleApplication1.Base1, ConsoleApplication1.I2)'

I thought the compiler could distinguish between two methods using the "where" clauses

Upvotes: 6

Views: 319

Answers (3)

Alok
Alok

Reputation: 274

Constraint cant be use to resolve association.

Upvotes: 0

e71
e71

Reputation: 93

Constraints are not part of the signature. For details see Eric Lippert article on the topic.

Upvotes: 3

Mike Cowan
Mike Cowan

Reputation: 919

Constraints are not part of the signature for methods and thus are not used for resolution.

Upvotes: 13

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