Question

This is probably a stupid question but, I have a method I use to make the syntax of a page a little more easy to read

    public void Do(Delegate method, DispatcherPriority priority = DispatcherPriority.Normal)
    {
        this.Window.Dispatcher.BeginInvoke(method, DispatcherPriority.Background);
    }

then I can write

        Do(new Action(() =>
        {
            //DoStuff()
        }));

However, I’d like to move the Action up into the Do Method so I can write more Simply:

        Do(() =>
        {
            //DoStuff()
        }));

But I’m a bit sure how to write the contravariant parameter to do the Do Method?

Answer 1

Lambdas are untyped, so this is not possible.

If you don’t care about method-arguments, which appears to be the case, why not change the method signature to :

public void Do(Action method,
               DispatcherPriority priority = DispatcherPriority.Normal)

Then, the second sample will work fine since the compiler will be able to implicitly convert the lambda to an Action.

If you really want to accept an instance of any delegate-type that represents a method that takes no arguments, you’ll have to stick to something like what you currently have.