Table of Contents

BLAZMVVM0001: ViewModelBase Inheritance

Summary

ViewModels should inherit from ViewModelBase to ensure proper MVVM pattern implementation and lifecycle management.

Description

This analyzer ensures that classes named with the "ViewModel" suffix inherit from the Blazing.Mvvm.ComponentModel.ViewModelBase class. This is essential for proper integration with the Blazing.MVVM framework's lifecycle management, property change notification, and navigation features.

Severity

Warning - This should be addressed to ensure proper MVVM functionality.

Why This Rule Exists

  • Ensures proper INotifyPropertyChanged implementation
  • Provides lifecycle hooks (OnInitialized, OnNavigatedTo, etc.)
  • Enables automatic property change notifications
  • Integrates with the framework's dependency injection
  • Provides access to navigation and messenger services

✅ DO: Correct Usage

using Blazing.Mvvm.ComponentModel;

// ✅ Correct: Inherits from ViewModelBase
public class ProductViewModel : ViewModelBase
{
    public string Name { get; set; }
}

// ✅ Correct: Inherits from ObservableObject (CommunityToolkit.Mvvm)
using CommunityToolkit.Mvvm.ComponentModel;

public partial class UserViewModel : ObservableObject
{
    [ObservableProperty]
    private string _username;
}

// ✅ Correct: Inherits from custom base that extends ViewModelBase
public class CustomViewModelBase : ViewModelBase
{
    // Custom shared logic
}

public class OrderViewModel : CustomViewModelBase
{
    // Specific logic
}

❌ DON'T: Incorrect Usage

// ❌ Wrong: No base class
public class ProductViewModel
{
    public string Name { get; set; }
}

// ❌ Wrong: Implements INotifyPropertyChanged manually
using System.ComponentModel;

public class UserViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    private string _name;
    public string Name
    {
        get => _name;
        set
        {
            _name = value;
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Name)));
        }
    }
}

// ❌ Wrong: Inherits from ComponentBase (this is for Views, not ViewModels)
using Microsoft.AspNetCore.Components;

public class OrderViewModel : ComponentBase
{
    // This is mixing View and ViewModel concerns
}

How to Fix

Option 1: Inherit from ViewModelBase

// Before
public class ProductViewModel
{
    public string Name { get; set; }
}

// After
using Blazing.Mvvm.ComponentModel;

public class ProductViewModel : ViewModelBase
{
    public string Name { get; set; }
}

Option 2: Use ObservableObject from CommunityToolkit.Mvvm

// Before
public class ProductViewModel
{
    private string _name;
    public string Name
    {
        get => _name;
        set => _name = value;
    }
}

// After
using CommunityToolkit.Mvvm.ComponentModel;

public partial class ProductViewModel : ObservableObject
{
    [ObservableProperty]
    private string _name;
}

Code Fix

This analyzer provides an automatic code fix that:

  1. Adds : ViewModelBase to the class declaration
  2. Adds the necessary using Blazing.Mvvm.ComponentModel; directive
  • BLAZMVVM0002: ViewModelDefinition Attribute - Ensures proper DI registration
  • BLAZMVVM0008: Observable Property - Validates property notification patterns

Additional Resources

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