Question

How do I get at the attribute of the parameter in the following code?

public void SomeMethod([SomeAttribute] string s)
{
    var someAttribute = ?
}

And I realize the attribute isn’t generally for use inside the method it’s on… just keeping the example simple though.

Answer 1

First you need a MethodInfo:

var method = typeof(SomeType).GetMethod("SomeMethod");

Then you can check for existence:

bool hasAttrib = Attribute.IsDefined(
    method.GetParameters()[0], typeof(SomeAttribute));

or get an instance (more expensive):

var attrib = (SomeAttribute) Attribute.GetCustomAttribute(
    method.GetParameters()[0], typeof(SomeAttribute));