ViewModelBase¶

The ViewModelBase is a foundational class for implementing the MVVM (Model-View-ViewModel) pattern. It provides built-in support for property change notifications, disposal patterns, and optional logging.

Overview¶

ViewModelBase implements INotifyPropertyChanged and IDisposable, making it ideal as a base class for view models in WPF, WinForms, and other UI frameworks that support data binding and property notifications.

Features¶

INotifyPropertyChanged support: Automatically notifies UI controls when properties change
Property change tracking: The SetField<T> method handles equality checks and notifications
Optional logging: Integrates with the TA.Utilities logging infrastructure
Disposal pattern: Implements the standard Dispose pattern for resource cleanup

Basic Usage¶

Create a view model by inheriting from ViewModelBase:

using TA.Utils.Core.MVVM;

public class MyViewModel : ViewModelBase
{
    private string _name;

    public string Name
    {
        get => _name;
        set => SetField(ref _name, value);
    }

    public MyViewModel() : base()
    {
        // Initialize your view model
    }
}

SetField Method¶

The SetField<T> method handles property updates with automatic change notifications:

protected bool SetField<T>(ref T field, T value, [CallerMemberName] string? propertyName = null)

Parameters¶

field: A reference to the backing field
value: The new value to set
propertyName: The property name (automatically populated via CallerMemberName)

Return Value¶

Returns true if the value was changed, false if the value was already the same.

Example¶

public class PersonViewModel : ViewModelBase
{
    private string _firstName;
    private int _age;

    public string FirstName
    {
        get => _firstName;
        set => SetField(ref _firstName, value);  // Auto-uses property name "FirstName"
    }

    public int Age
    {
        get => _age;
        set => SetField(ref _age, value);
    }
}

Logging Integration¶

When creating a view model, you can optionally pass an ILog instance for diagnostic logging:

var log = new SomeLoggerService();
var viewModel = new MyViewModel(log);

If no logger is provided, a DegenerateLoggerService (no-op logger) is used by default.

Handling Disposal¶

Override the Dispose(bool disposing) method to clean up any resources:

public class MyViewModel : ViewModelBase
{
    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            // Release managed resources here
            // Example: unsubscribe from events, dispose timers, etc.
        }
        base.Dispose(disposing);
    }
}

INotifyPropertyChanged Events¶

Subscribe to property change notifications:

var viewModel = new MyViewModel();

viewModel.PropertyChanged += (sender, e) =>
{
    if (e.PropertyName == nameof(viewModel.Name))
    {
        Console.WriteLine("Name changed!");
    }
};

viewModel.Name = "Alice";  // Triggers PropertyChanged event

Thread Safety¶

Property changes are not inherently thread-safe. If you need to update properties from worker threads, ensure you invoke the change notification on the UI thread using an appropriate dispatcher for your platform.