Anonymous types based in Interface

Question

Can I create anonymous implementations of an interface , in a way similar to the way

delegate() { // type impl here , but not implementing any interface}

Something on the lines of

new IInterface() { // interface methods impl here }

The situations where I see them to be useful are for specifying method parameters which are interface types, and where creating a class type is too much code.

For example , consider like this :

    public void RunTest()
    {
        Cleanup(delegate() { return "hello from anonymous type"; });
    }

    private void Cleanup(GetString obj)
    {
        Console.WriteLine("str from delegate " + obj());
    }

    delegate string GetString();

how would this be achieved if in the above code , the method Cleanup had an interface as a parameter , without writing a class definition ? ( I think Java allows expressions like new Interface() ... )

See also http://stackoverflow.com/questions/4287288 – BlueRaja - Danny Pflughoeft Mar 02 '11 at 23:23 — BlueRaja - Danny Pflughoeft, Mar 02 '11 at 23:23

score 5 · Answer 1 · answered Mar 02 '11 at 23:30

5

You may take a look at impromptu-interface. Allow you to wrap any object with a Duck Typing Interface.

answered Mar 02 '11 at 23:30

Kalman Speier

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I'd like to add it really is any object, including dynamic objects and anonymous objects. – jbtule Mar 02 '11 at 23:41
I would like to first understand how this thing works exactly .. +1 for the interesting link – Bhaskar Mar 03 '11 at 00:19
@Bhaskar it emits a lightweight proxy that uses the DLR to forward invocation to the orignal object. Essential it does the nontrivial work @Marc-Gravell was referring and uses the DLR as glue between the interface and an implementation, dynamic or otherwise. – jbtule Mar 03 '11 at 01:11
@jbtule, exactly. Also I think it's way faster than reflection. – Kalman Speier Mar 03 '11 at 06:58

score 3 · Accepted Answer · answered Mar 02 '11 at 23:20

There is no standard language syntax for that. To create an implementation of IInterface on the fly you could use Reflection.Emit and maybe something involving generics and/or Action<...>/Func<...> (with or without Expression), but it is a non-trivial amount of work.

Essentially, this is what many of the mocking frameworks do. Look to them, perhaps.

score 0 · Answer 3 · answered Mar 02 '11 at 23:25

0

private void CleanUp(Func<string> obj){
  Console.WriteLine("str from delegate " + obj.Invoke());
}

public void RunTest(){
   Cleanup(() => "hello from anonymous type");
 }

although not really implementing for an Interface...

answered Mar 02 '11 at 23:25

Sunny

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Anonymous types based in Interface

3 Answers3