wpf

name wpf description Build and modernize WPF applications on .NET with correct XAML, data binding, commands, threading, styling, and Windows desktop migration decisions. USE FOR: working on WPF UI, MVVM, binding, commands, or desktop modernization; migrating WPF from .NET Framework to .NET; integrating newer Windows capabilities into a WPF app. DO NOT USE FOR: unrelated stacks; generic tasks that do not need this specific guidance. INVOKES: inspect the repository context, edit targeted files, and run relevant build, test, lint, or validation commands when changes are made. compatibility Requires a WPF project on .NET or .NET Framework. WPF Trigger On working on WPF UI, MVVM, binding, commands, or desktop modernization migrating WPF from .NET Framework to .NET integrating newer Windows capabilities into a WPF app implementing data binding, styles, templates, or control customization Documentation WPF Overview Data Binding Overview MVVM Toolkit Introduction Styles and Templates Migration Guide References patterns.md - MVVM patterns, binding patterns, command patterns, and reusable architectural approaches anti-patterns.md - Common WPF mistakes and how to avoid them Workflow Confirm Windows-only scope — WPF is Windows-only even when the wider .NET stack is cross-platform Apply MVVM pattern — keep views dumb, logic in ViewModels, use commands Manage data binding explicitly — choose correct binding modes, validate at runtime Use styles and templates deliberately — keep UI composable, avoid page-specific hacks Handle threading correctly — use Dispatcher for UI updates, async/await for long operations Validate both designer and runtime — XAML composition failures often surface only at runtime Current Upstream Notes The August 2026 WPF overview reiterates WPF as a Windows-only desktop UI stack with XAML, data binding, styling, templates, resources, and vector/rich-media composition. Keep WPF-specific guidance separate from WinUI or MAUI unless the task is explicitly a migration or comparison. WPF exists on both .NET Framework and modern .NET. For modernization work, inventory compatibility constraints and use the current desktop migration guidance before moving project files, interop, deployment, or XAML resource dictionaries. Project Structure MyWpfApp/ ├── MyWpfApp/ │ ├── App.xaml # Application entry │ ├── MainWindow.xaml # Main window │ ├── Views/ # XAML views/windows │ ├── ViewModels/ # MVVM ViewModels │ ├── Models/ # Domain models │ ├── Services/ # Business logic │ ├── Converters/ # Value converters │ ├── Resources/ # Styles, templates, dictionaries │ └── Controls/ # Custom controls └── MyWpfApp.Tests/ MVVM Pattern ViewModel with MVVM Toolkit public partial class CustomersViewModel : ObservableObject { private readonly ICustomerService _customerService; [ ObservableProperty ] private ObservableCollection<Customer> _customers = []; [ ObservableProperty ] [ NotifyCanExecuteChangedFor(nameof(SaveCommand)) ] private Customer? _selectedCustomer; [ ObservableProperty ] [ NotifyCanExecuteChangedFor(nameof(RefreshCommand)) ] private bool _isLoading; public CustomersViewModel ( ICustomerService customerService ) { _customerService = customerService; } [ RelayCommand(CanExecute = nameof(CanRefresh)) ] private async Task RefreshAsync () { IsLoading = true ; try { var items = await _customerService.GetAllAsync(); Customers = new ObservableCollection<Customer>(items); } finally { IsLoading = false ; } } private bool CanRefresh () => !IsLoading; [ RelayCommand(CanExecute = nameof(CanSave)) ] private async Task SaveAsync () { if (SelectedCustomer is null ) return ; await _customerService.SaveAsync(SelectedCustomer); } private bool CanSave () => SelectedCustomer is not null ; } View Binding < Window x:Class = "MyWpfApp.Views.CustomersView" xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml" xmlns:vm = "clr-namespace:MyWpfApp.ViewModels" d:DataContext = "{d:DesignInstance Type=vm:CustomersViewModel}" > < Grid > < Grid.RowDefinitions > < RowDefinition Height = "Auto" /> < RowDefinition Height = "*" /> </ Grid.RowDefinitions > < ToolBar Grid.Row = "0" > < Button Content = "Refresh" Command = "{Binding RefreshCommand}" /> < Button Content = "Save" Command = "{Binding SaveCommand}" /> </ ToolBar > < DataGrid Grid.Row = "1" ItemsSource = "{Binding Customers}" SelectedItem = "{Binding SelectedCustomer}" AutoGenerateColumns = "False" > < DataGrid.Columns > < DataGridTextColumn Header = "Name" Binding = "{Binding Name}" /> < DataGridTextColumn Header = "Email" Binding = "{Binding Email}" /> </ DataGrid.Columns > </ DataGrid > </ Grid > </ Window > Dependency Injection public partial class App : Application { private readonly IHost _host; public App () { _host = Host.CreateDefaultBuilder() .ConfigureServices((context, services) => { // Services services.AddSingleton<ICustomerService, CustomerService>(); services.AddSingleton<INavigationService, NavigationService>(); // ViewModels services.AddTransient<CustomersViewModel>(); services.AddTransient<CustomerDetailViewModel>(); // Views services.AddTransient<MainWindow>(); services.AddTransient<CustomersView>(); }) .Build(); } protected override async void OnStartup ( StartupEventArgs e ) { await _host.StartAsync(); var mainWindow = _host.Services.GetRequiredService<MainWindow>(); mainWindow.Show(); base .OnStartup(e); } protected override async void OnExit ( ExitEventArgs e ) { await _host.StopAsync(); _host.Dispose(); base .OnExit(e); } } Data Binding Modes <!-- OneTime: Read once at initialization --> < TextBlock Text = "{Binding CreatedDate, Mode=OneTime}" /> <!-- OneWay: Source to target only (default for most properties) --> < TextBlock Text = "{Binding Name, Mode=OneWay}" /> <!-- TwoWay: Bidirectional synchronization --> < TextBox Text = "{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" /> <!-- OneWayToSource: Target to source only --> < TextBox Text = "{Binding SearchFilter, Mode=OneWayToSource}" /> Value Converters public class BooleanToVisibilityConverter : IValueConverter { public object Convert ( object value , Type targetType, object parameter, CultureInfo culture ) { if ( value is bool boolValue) { return boolValue ? Visibility.Visible : Visibility.Collapsed; } return Visibility.Collapsed; } public object ConvertBack ( object value , Type targetType, object parameter, CultureInfo culture ) { return value is Visibility.Visible; } } // Multi-value converter public class MultiplyConverter : IMultiValueConverter { public object Convert ( object [] values, Type targetType, object parameter, CultureInfo culture ) { if (values.Length == 2 && values[ 0 ] is double a && values[ 1 ] is double b) { return a * b; } return 0.0 ; } public object [] ConvertBack ( object value , Type[] targetTypes, object parameter, CultureInfo culture ) { throw new NotImplementedException(); } } Styles and Templates Resource Dictionary < ResourceDictionary xmlns = "http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x = "http://schemas.microsoft.com/winfx/2006/xaml" > <!-- Implicit style for all Buttons --> < Style TargetType = "Button" > < Setter Property = "Padding" Value = "10,5" /> < Setter Property = "Margin" Value = "5" /> < Setter Property = "Background" Value = "#0078D4" /> < Setter Property = "Foreground" Value = "White" /> < Setter Property = "Template" > < Setter.Value > < ControlTemplate TargetType = "Button" > < Border Background = "{TemplateBinding Background}" CornerRadius = "4" Padding = "{TemplateBinding Padding}" > < ContentPresenter HorizontalAlignment = "Center" VerticalAlignment = "Center" /> </ Border > </ ControlTemplate > </ Setter.Value > </ Setter > </ Style > <!-- Named style --> < Style x:Key = "DangerButton" TargetType = "Button" BasedOn = "{StaticResource {x:Type Button}}" > < Setter Property = "Background" Value = "#D32F2F" /> </ Style > </ ResourceDictionary > Threading and Dispatcher // Update UI from background thread await Task.Run( async () => { var data = await LoadDataAsync(); // Must use Dispatcher to update UI Application.Current.Dispatcher.Invoke(() => { Items.Clear(); foreach ( var item in data) { Items.Add(item); } }); }); // Better: Use async/await properly private async Task LoadDataAsync () { IsLoading = true ; try { // This runs on background thread var data = await _service.GetDataAsync(); // This automatically marshals to UI thread Items = new ObservableCollection<Item>(data); } finally { IsLoading = false ; } } Anti-Patterns to Avoid Anti-Pattern Why It's Bad Better Approach Logic in code-behind Hard to test, tight coupling Use MVVM with ViewModels Synchronous blocking calls UI freezes Use async/await Manual INotifyPropertyChanged Boilerplate, error-prone Use MVVM Toolkit attributes Hardcoded colors/sizes Inconsistent, hard to theme Use resource dictionaries Direct Dispatcher.Invoke everywhere Complex, error-prone Prefer async/await marshaling God ViewModel Unmaintainable Split into focused ViewModels Skipping binding validation Runtime errors hidden Use ValidatesOnDataErrors Event handlers for everything Memory leaks, coupling Use commands and bindings Best Practices Use compiled bindings in .NET 5+: Enable x:CompileBindings="True" for performance Implement INotifyDataErrorInfo for validation: [ ObservableProperty ] [ NotifyDataErrorInfo ] [ Required(ErrorMessage = "Name is required" ) ] [ MinLength(2, ErrorMessage = "Name must be at least 2 characters" ) ] private string _name = string .Empty; Use weak event patterns for long-lived subscriptions: WeakEventManager<Source, EventArgs>.AddHandler(source, "EventName" , Handler); Virtualize large collections: < ListBox VirtualizingPanel.IsVirtualizing = "True" VirtualizingPanel.VirtualizationMode = "Recycling" ItemsSource = "{Binding LargeCollection}" /> Freeze Freezables when possible: var brush = new SolidColorBrush(Colors.Blue); brush.Freeze(); // Thread-safe, better performance Use design-time data: < Window d:DataContext = "{d:DesignInstance Type=vm:MainViewModel, IsDesignTimeCreatable=True}" > Testing [ Fact ] public async Task RefreshCommand_LoadsCustomers () { var mockService = new Mock<ICustomerService>(); mockService.Setup(s => s.GetAllAsync()) .ReturnsAsync( new [] { new Customer { Name = "Test" } }); var viewModel = new CustomersViewModel(mockService.Object); await viewModel.RefreshCommand.ExecuteAsync( null ); Assert.Single(viewModel.Customers); Assert.Equal( "Test" , viewModel.Customers[ 0 ].Name); } [ Fact ] public void SaveCommand_CannotExecute_WhenNoSelection () { var mockService = new Mock<ICustomerService>(); var viewModel = new CustomersViewModel(mockService.Object); viewModel.SelectedCustomer = null ; Assert.False(viewModel.SaveCommand.CanExecute( null )); } Deliver cleaner WPF views and view-model boundaries safer binding and threading behavior migration guidance grounded in actual Windows constraints MVVM pattern with testable ViewModels Validate binding and command flows are explicit code-behind is not carrying hidden business logic Windows-only assumptions are acknowledged threading and dispatcher usage is correct styles and resources are properly organized