WPF Layer CakeC#, C++/CLI and C

Andy Dentwww.andydent.com

May 2009

Wandering in WPF

• Continuum of structuring a WPF program:• Ain’t it cool – do as much in XAML as possible,

binding data and all commands/events.• Events bound in XAML, commands in code.• Bind data only in XAML.• XAML for layout, code for all bindings.• Silly opposite extreme – no XAML

<Window.CommandBindings> <CommandBinding Command="{x:Static w:TestDespatchWindow.cmdShow2}" Executed="OnShow2" /> </Window.CommandBindings> <Window.InputBindings> <KeyBinding Key="T" Modifiers="Control" Command="{x:Static w:TestDespatchWindow.cmdShow2}" /> </Window.InputBindings> <DockPanel> <Menu DockPanel.Dock="Top"> <MenuItem Header="_File" > <MenuItem Header="E_xit" Command="Close" /> </MenuItem> <MenuItem Header="Test"> <MenuItem Command="{x:Static w:TestDespatchWindow.cmdShow2}" /> </MenuItem> </Menu> <StackPanel Margin="0,8,0,0"> <Button x:Name="Show2EventBased" Margin="10,2,10,2" Click="OnShow2" Content="Show2 via WPF Event"/> <Button x:Name="Show2Command" Command="{x:Static w:TestDespatchWindow.cmdShow2}" Margin="10,2,10,2" Content="Show2 via WPF"/> <Button x:Name="Show2IndirectCommand" Margin="10,2,10,2" Content="Show2 via DLL" />

public partial class WindowWithCommandVM : Window{ public WindowWithCommandVM() { InitializeComponent(); mBackend = new BackedCommandViewModel( "Fred Nerk", "10 Bloggs Ave\nToon Town", true);... DataContext = mBackend; NameEntry.SetBinding( TextBox.TextProperty, new Binding("Name") {Mode = BindingMode.TwoWay} );... CNTL_Lower.Command = mBackend.cmdLower; CommandBindings.Add( new CommandBinding(mBackend.cmdLower, mBackend.CommandSingleEntryPoint) );

public ref class BackedCommandViewModel : public INotifyPropertyChanged { public: BackedCommandViewModel( String^ _name, String^ _address);... void CommandSingleEntryPoint( Object^ sender, ExecutedRoutedEventArgs^ e); property String^ Name { String^ get(); void set(String^ s); }; property String^ Address { String^ get();...

property RoutedCommand^ cmdLower { RoutedCommand^ get(); };...

virtual event PropertyChangedEventHandler^ PropertyChanged;

private: void OnPropertyChanged(String^ name) { PropertyChanged(this, gcnew PropertyChangedEventArgs(name)); }

Lessons Learned

• Don’t fight C# - do hookups of properties and commands in code-behind files.

• C++/CLI can define straightforward Property objects, events, delegates and commands.

• Debugging all the way works if you tell your app it should debug unmanaged code.

• Beware of #includes in C++/CLI – use referenced assemblies