Dispatcher BeginInvoke Syntax

The problem is that the compiler doesn't know what kind of delegate you're trying to convert the lambda expression to. You can fix that either with a cast, or a separate variable:

private void OnSaveCompleted(IAsyncResult result)
{        
    Dispatcher.BeginInvoke((Action) (() =>
    {
        context.EndSaveChanges(result);
    }));
}

or

private void OnSaveCompleted(IAsyncResult result)
{
    Action action = () =>
    {
        context.EndSaveChanges(result);
    };
    Dispatcher.BeginInvoke(action);
}

Answer by Jon Skeet is very good but there are other possibilities. I prefer "begin invoke new action" which is easy to read and to remember for me.

private void OnSaveCompleted(IAsyncResult result)
{       
    Dispatcher.BeginInvoke(new Action(() =>
    {
        context.EndSaveChanges(result);
    }));
}

or

private void OnSaveCompleted(IAsyncResult result)
{       
    Dispatcher.BeginInvoke(new Action(delegate
    {
        context.EndSaveChanges(result);
    }));
}

or

private void OnSaveCompleted(IAsyncResult result)
{       
    Dispatcher.BeginInvoke(new Action(() => context.EndSaveChanges(result)));
}

If your method does not require parameters, this is the shortest version I've found

Application.Current.Dispatcher.BeginInvoke((Action)MethodName);