Andy (Steve) De George
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title, ms.date, dev_langs, helpviewer_keywords, ms.assetid
| title | ms.date | dev_langs | helpviewer_keywords | ms.assetid | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| How to: Hook Up a Command to a Control with No Command Support | 03/30/2017 |
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dad08f64-700b-46fb-ad3f-fbfee95f0dfe |
How to: Hook Up a Command to a Control with No Command Support
The following example shows how to hook up a xref:System.Windows.Input.RoutedCommand to a xref:System.Windows.Controls.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.
Example
Windows Presentation Foundation (WPF) provides a library of common commands which application programmers encounter regularly. The classes which comprise the command library are: xref:System.Windows.Input.ApplicationCommands, xref:System.Windows.Input.ComponentCommands, xref:System.Windows.Input.NavigationCommands, xref:System.Windows.Input.MediaCommands, and xref:System.Windows.Documents.EditingCommands.
The static xref:System.Windows.Input.RoutedCommand objects which make up these classes do not supply command logic. The logic for the command is associated with the command with a xref:System.Windows.Input.CommandBinding. Many controls in WPF have built in support for some of the commands in the command library. xref:System.Windows.Controls.TextBox, for example, supports many of the application edit commands such as xref:System.Windows.Input.ApplicationCommands.Paste%2A, xref:System.Windows.Input.ApplicationCommands.Copy%2A, xref:System.Windows.Input.ApplicationCommands.Cut%2A, xref:System.Windows.Input.ApplicationCommands.Redo%2A, and xref:System.Windows.Input.ApplicationCommands.Undo%2A. The application developer does not have to do anything special to get these commands to work with these controls. If the xref:System.Windows.Controls.TextBox is the command target when the command is executed, it will handle the command using the xref:System.Windows.Input.CommandBinding that is built into the control.
The following shows how to use a xref:System.Windows.Controls.Button as the command source for the xref:System.Windows.Input.ApplicationCommands.Open%2A command. A xref:System.Windows.Input.CommandBinding is created that associates the specified xref:System.Windows.Input.CanExecuteRoutedEventHandler and the xref:System.Windows.Input.CanExecuteRoutedEventHandler with the xref:System.Windows.Input.RoutedCommand.
First, the command source is created. A xref:System.Windows.Controls.Button is used as the command source.
[!code-xamlcommandWithHandler#CommandHandlerCommandSource]
[!code-csharpCommandHandlerProcedural#CommandHandlerButtonCommandSource] [!code-vbCommandHandlerProcedural#CommandHandlerButtonCommandSource]
Next, the xref:System.Windows.Input.ExecutedRoutedEventHandler and the xref:System.Windows.Input.CanExecuteRoutedEventHandler are created. The xref:System.Windows.Input.ExecutedRoutedEventHandler simply opens a xref:System.Windows.MessageBox to signify that the command executed. The xref:System.Windows.Input.CanExecuteRoutedEventHandler sets the xref:System.Windows.Input.CanExecuteRoutedEventArgs.CanExecute%2A property to true. Normally, the can execute handler would perform more robust checks to see if the command could execute on the current command target.
[!code-csharpcommandWithHandler#CommandHandlerBothHandlers] [!code-vbcommandWithHandler#CommandHandlerBothHandlers]
Finally, a xref:System.Windows.Input.CommandBinding is created on the root xref:System.Windows.Window of the application that associates the routed events handlers to the xref:System.Windows.Input.ApplicationCommands.Open%2A command.
[!code-xamlcommandWithHandler#CommandHandlerCommandBinding]
[!code-csharpCommandHandlerProcedural#CommandHandlerBindingInit] [!code-vbCommandHandlerProcedural#CommandHandlerBindingInit]