SimpleViewModel

A lightweight WPF ViewModel framework with automatic source generation that eliminates boilerplate code while maintaining full control over your view models.

Features

• Zero Boilerplate Commands: Transform methods into ICommand properties with a simple [Command] attribute
• Automatic Property Binding: Generate observable properties from fields using [Bind] attribute
• Source Generation: All code generation happens at compile time with no runtime reflection
• Lightweight: Minimal dependencies and overhead
• Type Safe: Full IntelliSense support and compile-time validation
• WPF Optimized: Built specifically for WPF applications with proper CommandManager integration

Table of Contents

• Quick Start
• Advanced Features
• How It Works
• Generated Code Example
• Best Practices
• Troubleshooting
• Requirements
• Contributing

Quick Start

Installation

<PackageReference Include="SimpleViewModel" Version="0.9.7" />

Basic Usage

1. Create a ViewModel:

using SimpleViewModel;
using SimpleViewModel.BaseClasses;

[ViewModel]
public partial class MainViewModel
{
    [Command]
    public void SaveData()
    {
        // Your save logic here
        MessageBox.Show("Data saved!");
    }

    [Command] 
    public void LoadData()
    {
        // Your load logic here
        MessageBox.Show("Data loaded!");
    }
}

2. Bind to XAML:

<Window x:Class="MyApp.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <StackPanel>
        <Button Content="Save" Command="{Binding SaveDataCommand}" />
        <Button Content="Load" Command="{Binding LoadDataCommand}" />
    </StackPanel>
</Window>

3. Set DataContext:

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = new MainViewModel();
    }
}

That's it! The source generator automatically creates SaveDataCommand and LoadDataCommand properties for you.

Advanced Features

Observable Properties

Use the [Bind] attribute to automatically generate observable properties:

[ViewModel]
public partial class UserViewModel
{
    [Bind]
    private string _firstName = "";
    
    [Bind]
    private string _lastName = "";
    
    [Bind]
    private int _age;
}

Generated code includes proper INotifyPropertyChanged implementation:

public string FirstName
{
    get => _firstName;
    set => SetProperty(ref _firstName, value);
}

Property Change Callbacks

Add custom logic when properties change:

[ViewModel]
public partial class UserViewModel
{
    [Bind(OnChangeMethodName = nameof(OnNameChanged))]
    private string _name = "";
    
    private void OnNameChanged()
    {
        // Custom logic when name changes
        Console.WriteLine($"Name changed to: {_name}");
    }
}

Command with CanExecute

Commands can include conditional execution logic:

[ViewModel]
public partial class DocumentViewModel
{
    [Bind]
    private string _selectedItem = "";

    [Command(CanExecuteMethodName = nameof(CanDelete))]
    public void Delete()
    {
        // Delete logic here
        Console.WriteLine($"Deleting {_selectedItem}");
    }
    
    public bool CanDelete()
    {
        return !string.IsNullOrEmpty(_selectedItem);
    }
}

Command with Parameters

Commands automatically support parameters through the Execute method:

[ViewModel]
public partial class DocumentViewModel
{
    [Command]
    public void DeleteItem()
    {
        // Note: Parameter handling is done in the generated command class
        // The method itself doesn't need to accept parameters
    }
}

How It Works

SimpleViewModel uses Roslyn source generators to analyze your code at compile time and automatically generate:

1. Partial ViewModel Class: Extends your class to inherit from BaseViewModel
2. Command Classes: Each [Command] method gets a corresponding command class that inherits from BaseCommand
3. Command Properties: Properties that expose the commands for data binding (lazily initialized)
4. Observable Properties: Properties with INotifyPropertyChanged support for [Bind] fields

All generated code is available in IntelliSense and can be debugged normally.

Generated Code Example

Your Code:

[ViewModel]
public partial class MyViewModel
{
    [Command]
    public void DoSomething() => Console.WriteLine("Done!");
}

Generated ViewModel Extension:

public partial class MyViewModel : BaseViewModel
{
    private Command_DoSomething? _DoSomethingCommand { get; set; }
    public Command_DoSomething DoSomethingCommand => _DoSomethingCommand ??= new(this);
}

Generated Command Class:

public sealed class Command_DoSomething : BaseCommand
{
    private readonly MyViewModel vm;
    
    public Command_DoSomething(MyViewModel vm)
    {
        this.vm = vm;
    }
    
    public override void Execute(object? parameter)
    {
        vm.DoSomething();
    }
}

Best Practices

1. Use Partial Classes: Always mark your view models as partial to allow source generation
2. Apply ViewModel Attribute: Use [ViewModel] on your class - the generator automatically makes it inherit from BaseViewModel
3. Field Naming: Use underscore prefixes for fields marked with [Bind] (e.g., _title becomes Title property)
4. Async Commands: For async operations, use async void in command methods
5. Parameter Validation: Commands receive parameters through the Execute(object? parameter) method in the generated class
6. Dependency Injection: Use constructor injection for services and dependencies

Troubleshooting

Generator Not Running

If the source generator isn't creating commands:

1. Ensure you have the [ViewModel] attribute on your class
2. Make sure the class is marked as partial
3. Check that methods have the [Command] attribute and are public
4. Verify fields have the [Bind] attribute for observable properties
5. Clean and rebuild your solution

Missing Commands in XAML

If commands aren't appearing in XAML IntelliSense:

1. Rebuild the project to trigger source generation
2. Check that the generated files are created (enable <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles> to see them)
3. Ensure proper namespace imports in XAML

Common Issues

• Fields not generating properties: Make sure fields are marked with [Bind] and are private
• Commands not working: Ensure methods are public and marked with [Command]
• CanExecute not working: Verify the method name in CanExecuteMethodName exists and is public with bool return type

Requirements

• .NET 8.0 or .NET 9.0 (Windows targets only)
• Windows (WPF applications only)
• C# 10.0 or later

License

MIT License - see LICENSE file for details.

Contributing

Contributions are welcome! Please feel free to submit issues and pull requests.

Repository

• 🏠 GitHub: https://github.com/DerekGooding/SimpleViewModel
• 📦 NuGet: https://www.nuget.org/packages/SimpleViewModel/
• 🐛 Issues: https://github.com/DerekGooding/SimpleViewModel/issues

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