I wanna tell my Wcf service contract which class is the known type. I find the answer in MSDN. I must define a static class like below:

// This class has the method named GetKnownTypes that returns a generic IEnumerable.

static class Helper

{

public static IEnumerable<Type> GetKnownTypes(ICustomAttributeProvider provider)

{

System.Collections.Generic.List<System.Type> knownTypes =

new System.Collections.Generic.List<System.Type>();

// Add any types to include here.

knownTypes.Add(typeof(Widget));

knownTypes.Add(typeof(Machine));

return knownTypes;

}

}

So I try to copy that:

type Helper =

static member GetKnownTypes(provider) = .......

[<ServiceKnownType("GetKnownTypes", typeof<Helper>)>]

type IMyInterface = .......

But I got a InvalidOperationException, There is now method named GetKnownTypes in type Helper.

I know define a static method is

static member XXX

But I cannot define a static class

static type MyClass = // error

How to define a static class?