Barry, Tnanx, You're right of course. But I need information about the *signature* of functions a delegate can bind to.
Piewie. ----- Original Message ----- From: "Barry Kelly" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, June 22, 2006 3:15 PM Subject: Re: [ADVANCED-DOTNET] Getting MemberInfo from a delegate Peter van der Weerd <[EMAIL PROTECTED]> wrote: > Suppose I typed the following delegate: > public delegate void MyDelegate(int i); > > This delegate is only bindable to functions getting an int as a parameter. Delegates are actually more flexible than the C# language permits. The delegate above is also bindable to static methods taking both an object and an int. The first parameter gets the value that was passed to CreateDelegate as the object instance (and it can be any object). ---8<--- using System; using System.Reflection; class App { delegate void Foo(int x); static void Main(string[] args) { MethodInfo myFoo = typeof(App).GetMethod("MyFoo", BindingFlags.Static | BindingFlags.NonPublic); Foo foo = (Foo) Delegate.CreateDelegate(typeof(Foo), null, myFoo); foo(42); } static void MyFoo(object obj, int x) { Console.WriteLine("obj is null: " + (obj == null)); Console.WriteLine("x: " + x); } } --->8--- > My question is: how can I get information to what type of functions a > delegate can bind to. > Basically I want to write a function which accepts a typeof(MyDelegate) > and > is able to check if the MemberInfo of a method is bindable to this > delegate. You've got all the information in the MethodInfo (parameter and return types) and in the delegate (find the Invoke method on the delegate type and look at its parameter and return types). The rules: * Return type on the method to bind can be covariant, or more derived than the original in the delegate. * Parameter types on the method to bind can be contravariant, or less derived than the original in the delegate. * Value types can't be coerced to reference types, so co/contravariance doesn't apply between int and object, for example. In other words, delegate dispatch never performs boxing or unboxing after the arguments have been converted to match the declared parameter types on the delegate. * A static method can optionally accept a reference argument from the delegate's "Target" property as the value of the first parameter. The value of the argument to CreateDelegate must be assignable to variables of the declared type of the first parameter if you use this. Again, the value passed to CreateDelegate may be a value type, but the parameter cannot: it must be a reference type. -- Barry -- http://barrkel.blogspot.com/ =================================== This list is hosted by DevelopMentor® http://www.develop.com View archives and manage your subscription(s) at http://discuss.develop.com =================================== This list is hosted by DevelopMentor® http://www.develop.com View archives and manage your subscription(s) at http://discuss.develop.com
