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Commands in WPF: Part I

On March 09, 2010 Articles | WPF
In this article we will see what Commands are and how we can use them in WPF.
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Introduction

In this article we will see what Commands are and how we can use them in WPF.

Commands

It is often helpful to focus on what the user wants our application to do. WPF supports this through the command abstraction - a command is an action the application performs at the user's request.

WPF's command system lets us treat them as different expressions of the same command.

The command system lets a UI element provide a single handler for a command, reducing clutter and improving the clarity of your code.

The way in which a command is invoked isn't usually important. Whether the user presses Ctrl-C, selects the Edit -> Copy menu item, or clicks the Copy button on the toolbar, the application's response should be the same in each case: it should copy the current selection to the clipboard.

So let's have a sample application that will describe the above described things.

Creating a WPF Application

Fire up Visual Studio 2008 and Create a WPF Application, name it as CommandsWPF.

CommandsWPF1.gif

Now let's have few controls that would fulfil our sample to understand Commands.

Such as some Buttons displaying Copy, Cut, and Paste. And obviously a Text Box that would be the target where we can see the application working.

CommandsWPF2.gif

The following is the XAML for reference:

CommandsWPF3.gif

Now we will see how Commands can be applied to the respective Clipboard Buttons.

Now run the application and see the output as, all the buttons are in disabled.

CommandsWPF4.gif

Even if you select the text nothing happens, that is because we haven't added the Target Control to handle.

Add the CommandTarget property and set the Bindings as follows:

CommandsWPF5.gif

Now run the application and see how we have achieved the Clipboard Commands in Buttons.

CommandsWPF6.gif

As soon as you select the Text the Cut and Copy Buttons are enabled.

CommandsWPF7.gif

As soon as you perform the Copy or Cut Commands operation Paste Button is enabled.

CommandsWPF8.gif

By default TextBox has the Clipboard as ContextMenu, so even if we don't add commands in Buttons the Menu is displayed.

CommandsWPF9.gif

Hope this article helps for the beginning in Commands in WPF. In next part we will explore more.

Diptimaya Patra

Visit in http://diptimayapatra.wordpress.com for latest articles.Facebook Page: https://www.facebook.com/MethodOfTried

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