Gets the value that represents the Help command.
Assembly: PresentationCore (in PresentationCore.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
The following example shows how to hook up a RoutedCommand to a Control which has built in support for the command. For a complete sample which hooks up commands to multiple sources, see the Create a Custom RoutedCommand Sample sample.
Windows Presentation Foundation (WPF) provides a library of common commands which application programmers encounter regularly. The classes which comprise the command library are: ApplicationCommands, ComponentCommands, NavigationCommands, MediaCommands, and EditingCommands.
The static RoutedCommand objects which make up these classes do not supply command logic. The logic for the command is associated with the command with a CommandBinding. Some controls have built in CommandBindings for some commands. This mechanism allows the semantics of a command to stay the same, while the actual implementation is can change. A TextBox, for example, handles the Paste command differently than a control designed to support images, but the basic idea of what it means to paste something stays the same. The command logic cannot be supplied by the command, but rather must be supplied by the control or the application.
Many controls in WPF do have built in support for some of the commands in the command library. TextBox, for example, supports many of the application edit commands such as Paste, Copy, Cut, Redo, and Undo. The application developer does not have to do anything special to get these commands to work with these controls. If the TextBox is the command target when the command is executed, it will handle the command using the CommandBinding that is built into the control.
The following shows how to use a MenuItem as the command source for the Paste command, where a TextBox is the target of the command. All the logic that defines how the TextBox performs the paste is built into the TextBox control.
A MenuItem is created and it's Command property is set to the Paste command. The CommandTarget is not explicitly set to the TextBox object. When the CommandTarget is not set, the target for the command is the element which has keyboard focus. If the element which has keyboard focus does not support the Paste command or cannot currently execute the paste command (the clipboard is empty, for example) then the MenuItem would be grayed out.
<Window x:Class="SDKSamples.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="MenuItemCommandTask" > <DockPanel> <Menu DockPanel.Dock="Top"> <MenuItem Command="ApplicationCommands.Paste" Width="75" /> </Menu> <TextBox BorderBrush="Black" BorderThickness="2" Margin="25" TextWrapping="Wrap"> The MenuItem will not be enabled until this TextBox gets keyboard focus </TextBox> </DockPanel> </Window>
' Window1 constructor Public Sub New() InitializeComponent() ' Instantiating UIElements. Dim mainPanel As New DockPanel() Dim mainMenu As New Menu() Dim pasteMenuItem As New MenuItem() Dim mainTextBox As New TextBox() ' Associating the MenuItem with the Paste command. pasteMenuItem.Command = ApplicationCommands.Paste ' Setting properties on the TextBox. mainTextBox.Text = "The MenuItem will not be enabled until this TextBox receives keyboard focus." mainTextBox.Margin = New Thickness(25) mainTextBox.BorderBrush = Brushes.Black mainTextBox.BorderThickness = New Thickness(2) mainTextBox.TextWrapping = TextWrapping.Wrap ' Attaching UIElements to the Window. Me.AddChild(mainPanel) mainMenu.Items.Add(pasteMenuItem) mainPanel.Children.Add(mainMenu) mainPanel.Children.Add(mainTextBox) ' Defining DockPanel layout. DockPanel.SetDock(mainMenu, Dock.Top) DockPanel.SetDock(mainTextBox, Dock.Bottom) End Sub
|How to: Hook Up a Command to a Control with No Command Support||The following example shows how to hook up a RoutedCommand to a Control which does not have built in support for the command. For a complete sample which hooks up commands to multiple sources, see the Create a Custom RoutedCommand Sample sample.|
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.