Question

This hasn’t done anything but cause the need for what would otherwise be unnecessary casting (or rather, caused me to pull down the codebase and make the change myself). Is there a reason for doing this?

References:

Source on Codeplex

Blog posting with source

Edit
Here’s an example:

DoCommand = new RelayCommand<AsyncCallback>((callBack) =>
{
    Console.WriteLine("In the Action<AsyncCallback>");
    SomeAsyncFunction((async_result) =>
    {
        Console.WriteLine("In the AsyncCallback");
        callBack.Invoke(new MyAsyncResult(true));
    });
});

DoCommand.Execute((iasyncresult) => Console.WriteLine(iasyncresult.IsCompleted));
//Where MyAsyncResult is a class implement IAsyncResult that sets IsCompleted in the constructor
// This will cause the "cannot cast lambda as object" error

Answer 1

Your error is due to the lambda not being able to be passed as an object. Instead try:

AsyncCallback callback = (iasyncresult) => Console.WriteLine(iasyncresult.IsCompleted);
DoCommand.Execute(callback);