基于MVVM Light的MahApps DialogCoordinator正确MVVM实现问询

Hey there! Let's work through getting that IDialogCoordinator injected into your ViewModels in the MyProject.Core project without a hitch. Here's a step-by-step breakdown of the common solutions:

1. Direct Injection (Core depends on MahApps) #

If you don't mind your Core project having a dependency on MahApps' dialog library, this is the quickest approach:

Step 1: Add MahApps Dialogs NuGet to Core #

First, install the MahApps.Metro.Controls.Dialogs NuGet package in your MyProject.Core class library. This lets the Core project recognize the IDialogCoordinator interface.

Step 2: Register DialogCoordinator in Presentation #

In your MyProject.Presentation WPF app (usually in App.xaml.cs or your ViewModelLocator), register the singleton instance of DialogCoordinator with MVVM Light's SimpleIoc:

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    
    // Register the DialogCoordinator singleton
    SimpleIoc.Default.Register<IDialogCoordinator>(() => DialogCoordinator.Instance);
    
    // Register your ViewModels here too
    SimpleIoc.Default.Register<MyViewModel>();
}

Step 3: Inject into ViewModel #

Now you can inject IDialogCoordinator directly into your Core ViewModel's constructor:

using MahApps.Metro.Controls.Dialogs;
using GalaSoft.MvvmLight;

namespace MyProject.Core.ViewModels
{
    public class MyViewModel : ViewModelBase
    {
        private readonly IDialogCoordinator _dialogCoordinator;

        // Constructor injection
        public MyViewModel(IDialogCoordinator dialogCoordinator)
        {
            _dialogCoordinator = dialogCoordinator;
            // Initialize commands or other logic here
        }

        // Example usage in a command
        private async void ShowDialog()
        {
            await _dialogCoordinator.ShowMessageAsync(this, "Success!", "Dialog injected correctly!");
        }
    }
}

2. Decoupled Approach (Core doesn't depend on MahApps) #

If you want to keep your Core project clean of UI framework dependencies, use dependency inversion by creating your own abstraction:

Step 1: Define a Dialog Service Interface in Core #

Create a simple interface in MyProject.Core that outlines the dialog functionality you need:

namespace MyProject.Core.Services
{
    public interface IDialogService
    {
        Task ShowMessageAsync(string title, string message);
        // Add other dialog methods (confirm, input, etc.) as needed
    }
}

Step 2: Implement the Service in Presentation #

In MyProject.Presentation, create a concrete implementation that uses MahApps' DialogCoordinator:

using MahApps.Metro.Controls.Dialogs;
using MyProject.Core.Services;

namespace MyProject.Presentation.Services
{
    public class MahAppsDialogService : IDialogService
    {
        private readonly IDialogCoordinator _dialogCoordinator;

        public MahAppsDialogService(IDialogCoordinator dialogCoordinator)
        {
            _dialogCoordinator = dialogCoordinator;
        }

        public async Task ShowMessageAsync(string title, string message)
        {
            // Use the injected DialogCoordinator to show the dialog
            await _dialogCoordinator.ShowMessageAsync(this, title, message);
        }
    }
}

Step 3: Register Services with SimpleIoc #

Back in your Presentation project's startup code, register both the IDialogCoordinator and your custom IDialogService:

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    
    SimpleIoc.Default.Register<IDialogCoordinator>(() => DialogCoordinator.Instance);
    SimpleIoc.Default.Register<IDialogService, MahAppsDialogService>();
    
    SimpleIoc.Default.Register<MyViewModel>();
}

Step 4: Inject Your Custom Service into ViewModel #

Now your Core ViewModel only depends on your own IDialogService, no MahApps references needed:

using MyProject.Core.Services;
using GalaSoft.MvvmLight;

namespace MyProject.Core.ViewModels
{
    public class MyViewModel : ViewModelBase
    {
        private readonly IDialogService _dialogService;

        public MyViewModel(IDialogService dialogService)
        {
            _dialogService = dialogService;
        }

        private async void ShowDialog()
        {
            await _dialogService.ShowMessageAsync("Success!", "Decoupled dialog service works!");
        }
    }
}

Common Troubleshooting Tips #

• "IDialogCoordinator not found": Make sure you've installed the correct MahApps NuGet package in the project where you're referencing the interface.
• Dialogs don't show up: Ensure you're passing the ViewModel instance (this) when calling dialog methods—MahApps uses this to find the associated window context.
• ViewModel not resolving: Double-check that your ViewModels are registered in SimpleIoc and that the ViewModelLocator is correctly set up in your XAML.

内容的提问来源于stack exchange，提问作者chrizator