⚡ MvvmGen

Your Friend Who Writes the Boilerplate for You

Hey there, welcome to the MvvmGen repository. MvvmGen is a lightweight and modern MVVM library (.NET Standard 2.0) built with C# Source Generators that helps you to apply the popular Model-View-ViewModel-pattern (MVVM) in your XAML applications that you build with WPF, WinUI, Uno Platform, Avalonia, Xamarin Forms, or .NET MAUI.

MvvmGen is licensed under the MIT license.

Get Started

Quick intro

In this quick intro, you'll learn that creating a ViewModel is a lot of fun with MvvmGen! 🔥

Installing the MvvmGen NuGet Package

Reference the NuGet package MvvmGen in your .NET application, and then you're ready to go:

Install-Package MvvmGen

MvvmGen will register itself as a C# source generator in your project, and it will be your friend who writes the boilerplate for you.

Generating a ViewModel class

To generate a ViewModel class, you create a new class, you mark it as partial, and you put MvvmGen's ViewModel attribute on the class:

using MvvmGen;

namespace MyWpfApp.ViewModel
{
  [ViewModel]
  public partial class EmployeeViewModel
  {
  }
}

The ViewModel attribute tells MvvmGen to generate another partial EmployeeViewModel class. Right now, it will be a class that looks like this:

using MvvmGen.Commands;
using MvvmGen.Events;
using MvvmGen.ViewModels;

namespace MyWpfApp.ViewModel
{
    partial class EmployeeViewModel : ViewModelBase
    {
        public EmployeeViewModel()
        {
            this.OnInitialize();
        }

        partial void OnInitialize();
    }
}

You can see that generated class in Visual Studio under Dependencies->Analyzers:

Beside the ViewModel attribute, you find many other attributes in the MvvmGen namespace that you can use to decorate your ViewModel class. These attributes allow you to build a full ViewModel like this:

using MvvmGen;
using MvvmGen.Events;

namespace MyWpfApp.ViewModel
{
  public record EmployeeSavedEvent(string FirstName, string LastName);

  [Inject(typeof(IEventAggregator))]
  [ViewModel]
  public partial class EmployeeViewModel
  {
    [Property] private string _firstName;
    [Property] private string _lastName;

    [Command(CanExecuteMethod = nameof(CanSave))]
    private void Save()
    {
      EventAggregator.Publish(new EmployeeSavedEvent(FirstName, LastName));
    }

    [CommandInvalidate(nameof(FirstName))]
    private bool CanSave()
    {
      return !string.IsNullOrEmpty(FirstName);
    }
  }
}

For this ViewModel, MvvmGen will generate the following partial class definition for you

using MvvmGen.Commands;
using MvvmGen.Events;
using MvvmGen.ViewModels;

namespace MyWpfApp.ViewModel
{
  partial class EmployeeViewModel : ViewModelBase
  {
    public EmployeeViewModel(MvvmGen.Events.IEventAggregator eventAggregator)
    {
      this.EventAggregator = eventAggregator;
      this.InitializeCommands();
      this.OnInitialize();
    }

    partial void OnInitialize();

    private void InitializeCommands()
    {
      SaveCommand = new DelegateCommand(_ => Save(), _ => CanSave());
    }

    public DelegateCommand SaveCommand { get; private set; }

    public string FirstName
    {
      get => _firstName;
      set
      {
        if (_firstName != value)
        {
          _firstName = value;
          OnPropertyChanged("FirstName");
        }
      }
    }

    public string LastName
    {
      get => _lastName;
      set
      {
        if (_lastName != value)
        {
          _lastName = value;
          OnPropertyChanged("LastName");
        }
      }
    }

    protected MvvmGen.Events.IEventAggregator EventAggregator { get; private set; }
    
    protected override void InvalidateCommands(string? propertyName)
    {
      base.InvalidateCommands(propertyName);
      if(propertyName == "FirstName")
      {
          SaveCommand.RaiseCanExecuteChanged();
      }
    }
  }
}