Question

I noticed in .NET 4.5 that the WPF Dispatcher had gotten a new set of methods to execute stuff on the Dispatcher’s thread called InvokeAsync. Before, .NET 4.5 we had Invoke and BeginInvoke which handled this syncronously and asynchronously respectively.

Besides the naming and the slightly different overloads available, are there any major differences between the BeginInvoke and the InvokeAsync methods?

Oh, and I already checked, both can be awaited:

private async Task RunStuffOnUiThread(Action action)
{
    // both of these works fine
    await dispatcher.BeginInvoke(action);
    await dispatcher.InvokeAsync(action);
}

Answer 1

There are no differences as the BeginInvoke method calls a private LegacyBeginInvokeImpl method which itslef calls the private method InvokeAsyncImpl (the method used by InvokeAsync). So it’s basically the same thing. It seems like it’s a simple refactoring, however it’s strange the BeginInvoke methods weren’t flagged as obsolete.

BeginInvoke :

public DispatcherOperation BeginInvoke(DispatcherPriority priority, Delegate method)
{
    return this.LegacyBeginInvokeImpl(priority, method, null, 0);
}

private DispatcherOperation LegacyBeginInvokeImpl(DispatcherPriority priority, Delegate method, object args, int numArgs)
{
    Dispatcher.ValidatePriority(priority, "priority");
    if (method == null)
    {
        throw new ArgumentNullException("method");
    }
    DispatcherOperation dispatcherOperation = new DispatcherOperation(this, method, priority, args, numArgs);
    this.InvokeAsyncImpl(dispatcherOperation, CancellationToken.None);
    return dispatcherOperation;
}

InvokeAsync :

public DispatcherOperation InvokeAsync(Action callback, DispatcherPriority priority)
{
    return this.InvokeAsync(callback, priority, CancellationToken.None);
}

public DispatcherOperation InvokeAsync(Action callback, DispatcherPriority priority, CancellationToken cancellationToken)
{
    if (callback == null)
    {
        throw new ArgumentNullException("callback");
    }
    Dispatcher.ValidatePriority(priority, "priority");
    DispatcherOperation dispatcherOperation = new DispatcherOperation(this, priority, callback);
    this.InvokeAsyncImpl(dispatcherOperation, cancellationToken);
    return dispatcherOperation;
}