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);
}