MVVM Dialogs is a framework simplifying the concept of opening dialogs from a view model when using MVVM in WPF (Windows Presentation Framework) or UWP (Universal Windows Platform). It enables the developer to easily write unit tests for view models in the same manner unit tests are written for other classes.

The framework has built in support for the following dialogs in WPF:

• Modal window
• Non-modal window
• Message box
• Open file dialog
• Save file dialog
• Folder browser dialog

The framework has built in support for the following dialogs in UWP:

• Content dialog
• Message dialog
• Single file picker
• Multiple files picker
• Save file picker
• Single folder picker

To open a modal window, decorate the view with the attached property DialogServiceViews.IsRegistered:

<UserControl
    x:Class="DemoApplication.Features.Dialog.Modal.Views.ModalDialogTabContent"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:md="https://github.com/fantasticfiasco/mvvm-dialogs"
    md:DialogServiceViews.IsRegistered="True">

  ...
  
</UserControl>

With the view registered the view model is now capable of opening a dialog using the interface IDialogService:

public class ModalDialogTabContentViewModel : INotifyPropertyChanged
{
    private readonly IDialogService dialogService;

    public ModalDialogTabContentViewModel(IDialogService dialogService)
    {
        this.dialogService = dialogService;
    }

    ...

    private void ShowDialog()
    {
        var dialogViewModel = new AddTextDialogViewModel();

        bool? success = dialogService.ShowDialog(this, dialogViewModel);
        if (success == true)
        {
            Texts.Add(dialogViewModel.Text);
        }
    }
}

With UWP you don't need to register the view, simply open the dialog using the interface IDialogService:

public class MainPageViewModel : INotifyPropertyChanged
{
    private readonly IDialogService dialogService;

    public MainPageViewModel(IDialogService dialogService)
    {
        this.dialogService = dialogService;
    }

    ...

    private async void ShowContentDialog()
    {
        var dialogViewModel = new AddTextContentDialogViewModel();

        ContentDialogResult result = await dialogService.ShowContentDialogAsync(dialogViewModel);
        if (result == ContentDialogResult.Primary)
        {
            Texts.Add(dialogViewModel.Text);
        }
    }
}

Dialogs in WPF that don't inherit from Window, or content dialogs in UWP that don't inherit from ContentDialog are called custom dialogs. These custom dialogs are supported, but in order for DialogService to know how to interact with them, you will have to implement the IWindow interface in WPF or IContentDialog in UWP.

If you want to include MVVM Dialogs in your project, you can install it directly from NuGet.

To install MVVM Dialogs, run the following command in the Package Manager Console:

PM> Install-Package MvvmDialogs

Thank you JetBrains for your important initiative to support the open source community with free licenses to your products.