Question

In some class method, A, I need to call a library method B, which takes as an IProgress<Object> as a parameter.

Normally, I might either implement IProgress<Object> as part of class where A resides, and then pass “this” to method B. Or perhaps I might create a new class whose only purpose is to implement IProgress<Object> and handle it correctly– then in this case I’d create an instance of that class and pass it to B.

But what I really want is to have my implementation of IProgress<Object> to appear right inside the method in which I’m calling B, so that there’s less of a visual disconnect between the calling code, and the IProgress<Object> implementation. (I consider my implementation of IProgress to be kind of a private, non-shared detail of the calling method and thus I don’t want my implementation of IProgress<Object> to be in a whole separate method of perhaps a whole other class).

What I’ve been trying to do is use a lambda in which I will define my short progress handling, and then somehow pass this lambda to B, like this:

method in class A {
...
Action<Object> Report = (m) => { // do something useful with m };

B(Report)
}

method B(IProgress<Object> reporter) {
   reporter.Report(some object)
}

Of course, I know why this won’t work as is – B is wanting an object that implements IProgress<Object> and I’m handing it an Action object instead.

Is there any way to achieve what I’m trying to achieve? (IE have my implementation if IProgress<Object> appear inside method A?

Answer 1

Delegates cannot implement interfaces (directly).

Two good options come to mind:

1. Change the definition of the method that you’re calling to take a delegate types instead of an IProgress type. (If possible; this would be the preferable option)

2. Create a new type that implements the interface that you need and takes a delegate as a parameter to implement that functionality.

And example of #2, while dependent on the interface, might look something like this:

interface IProgress<T>
{
    void doStuff(T param);
}

class LambdaProgress<T> : IProgress<T>
{
    Action<T> action;
    public LambdaProgress(Action<T> action)
    {
        this.action = action;
    }

    public void doStuff(T param)
    {
        action(param);
    }
}

then you’d be able to do something like:

B(new LambdaProgress<Object>(obj => ...));