CODEWITHSUNDEEP
c#reflectiondelegates
Nate Heinrich
Nate Heinrich

Reputation: 1805

CreateDelegate fails due to delegate signature mismatch

I am consuming a web service which has a number of methods (50) which create different objects.
example:
CreateObject1(Object1 obj, int arg2)
CreateObject2(Object2 obj, int arg2)
...
CreateObjectX(ObjectX obj, int arg2)

All Objects (Object1, Object2, ObjectX...) inherit from ObjectBase.

So I am trying to do this...

delegate void DlgtCreateObject(ObjectBase obj, int arg2);

public void CreateObject(ObjectBase obj, int arg2) 
{
    DlgtCreateObject dlgt;
    string objType;
    string operation;

    objType = obj.GetType().ToString();
    operation = "Create" + objType.Substring(objType.LastIndexOf(".") + 1);

    using (MyWebService service = new MyWebService())
    {

        dlgt = (DlgtCreateObject)Delegate.CreateDelegate(typeof(DlgtCreateObject),
                                                         service,
                                                         operation,
                                                         false,
                                                         true);
        dlgt(obj, arg2);
    }
}

Unfortunately this gives me a Failed to Bind exception. I believe this is because my delegate signature uses the ObjectBase as its first argument where the functions use the specific classes.

Is there a way around this?

Upvotes: 0

Views: 332

Answers (2)

Nate Heinrich
Nate Heinrich

Reputation: 1805

Right after posting I figured generics might be the answer, and indeed the following seems to do the trick...

delegate void DlgtCreateObject<T>(T obj, int arg2) where T : ObjectBase;

public void CreateObject<T>(T obj, int arg2) where T : ObjectBase; 
{
    DlgtCreateObject dlgt;
    string objType;
    string operation;

    objType = obj.GetType().ToString();
    operation = "Create" + objType.Substring(objType.LastIndexOf(".") + 1);

    using (MyWebService service = new MyWebService())
    {

        dlgt = (DlgtCreateObject<T>)Delegate.CreateDelegate(typeof(DlgtCreateObject<T>),
                                                 service,
                                                 operation,
                                                 false,
                                                 true);
        dlgt(obj, arg2);
    }
}

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1500953

If you're only trying to call the methods within here, I suggest you use Type.GetMethod and MethodBase.Invoke instead of going via delegates. Then you won't run into this problem.

Upvotes: 1

Related Questions