Can a C# custom attribute specify the type of method it is applied to?

Question

I know I can use [AttributeUsage(AttributeTargets.Method)] to make sure a custom attribute can only be applied to a method, but can I go further and get a compile-time error if the custom attribute is applied to a method with a signature other than the one I specify?

For example, can I create an attribute that can only be attached to a method that returns int and takes a single int parameter?

Answer 1

but can I go further and get a compile-time error if the custom attribute is applied to a method with a signature other than the one I specify?

No, you can't, this simply is not supported.

Answer 2

You can't do that, but you've a workaround: .NET Framework supports attributes on methods' input parameters and return values.

[MyAttribute1]
[return: MyAttribute2]
public int Method([MyAttribute3] int some)
{
    return "";
}

And the code inspecting the method can do things if the method has MyAttribute1 , MyAttribute2 and MyAttribute3 .

Depending on your needs, maybe this is too ugly, but I don't know your actual requirements!

Answer 3

You can apply an attribute during compilation using PostSharp. This link demonstrates Automatically Adding DataContract and DataMember Attributes