MahApps MessageBoxes using MVVM

As of 1.1.3-ALPHA* (to become 1.2.0) MahApps provides a helper to launch dialogs from a VM, which works in a multiple Window setup:

1) Use an attached property in your Window to register your view model with the dialog sub-system.

Assuming your View’s DataContext is set to the view model from where you want to launch the dialog, add these attributes:


2) Grab/inject DialogCoordinator:

new MainWindowViewModel(DialogCoordinator.Instance);

3) Show your dialog from the view model. Use "this" as the context so MahApps can marry your view model to the correct window:

_dialogCoordinator.ShowMessageAsync(this, "Message from VM", "MVVM based dialogs!")

I have created a wrapper to call the MahApps.Metro message dialog, cause I was having the same problem with my MVVM project. I had to create a list of opened windows, which the first window will always be my MainWindow.

Here's my DialogService code:

public async Task<MessageDialogResult> ShowMessage(string message, MessageDialogStyle dialogStyle)
    var metroWindow = (_openedViews.First() as MetroWindow);
    metroWindow.MetroDialogOptions.ColorScheme = MetroDialogColorScheme.Accented;

    return await metroWindow.ShowMessageAsync("MY TITLE", message, dialogStyle, metroWindow.MetroDialogOptions);

This code can be used to show dialogs with or without a result. You can notice that its return is a Task<MessageDialogResult>, so if you want to get the result, you can do just like that on your ViewModel:

MessageDialogResult result = await _dialog.ShowMessage("SOME MESSAGE HERE", MessageDialogStyle.AffirmativeAndNegative).ConfigureAwait(false);

if (result == MessageDialogResult.Affirmative)
    //Do something

By the way, if the method that calls the ShowMessage() needs a result, you MUST put async on the assignment, otherwise it won't work. (if you only want to show a message dialog, it's not necessary).

My project is using Framework 4.0, and I can only use async/await due to the package I had to install from NuGet. You can acces this link for the MSDN documentation of this package, and you can download the package here.

I hope it has solved your problem.


I have implemented a method on my DialogService to open any windows from any ViewModel. This method uses Microsoft Unity framework to instantiate my object, and then I call Show() to open itself. Before a call Show(), I add this window on a list.

See my code:

public void ShowView<T>(params ParameterOverride[] parameter)
    var window = UnityServiceConfigurator.Instance.Container.Resolve<T>(parameter) as MetroWindow;

    if (window != null)
        if (Application.Current.MainWindow != window)
            window.Owner = Application.Current.MainWindow;
            var ownerMetroWindow = (window.Owner as MetroWindow);

            if (!ownerMetroWindow.IsOverlayVisible())

        if (!_openedViews.Contains(window))


This is how I call from my ViewModel:


If you have only one window on your entire software, you can save its reference and use it to show the ShowMessageAsync() without needing to create a List only to use the First. Like this:

var metroWindow = (Application.Current.MainWindow as MetroWindow);