Damian Schenkelman’s Blog

Most developers are familiar with code snippets. They are really useful while developing code, mainly because they make some of the most common developing tasks easier and faster, by making us just fill in a couple of blanks.

This is great, but Julian had an idea that I believe will make the code snippets we created even more useful. He said: “What if we not only provide the code snippets, but we also add some guidance, links and tips based on our experience as Prism developers, that will help others with these common tasks”. Matias, Ezequiel and me thought this was a great idea, specially for people starting with Prism. The guidance offered in the snippets will provide insight about how Prism works, leading to better and faster development. This guidance can simply be deleted once the code is put into place as it is just composed of code comments.

Without further introduction, the code snippets we created are useful for the most common ways of performing the following tasks (between brackets how to insert the snippet in code):

• View Discovery (prismviewdisc)
• View Injection (prismviewinj)
• Event Publishing (prismeventpub)
• Event Subscribing (prismeventsub)
• Command with attached behavior (prismcmdbehavior, this was updated from this snippet)

Below you can find a picture of the generated code for the Event Subscription snippet, so you can get an idea of about these snippets with tips:

Pre-Requirements

1. Download the Snippet Visual Studio installer and run the installer (the snippets are provided “AS IS” with no warranties and confers no rights). You can also get the .zip file from here if you want to edit the snippets.

I hope the snippets help you learn Prism while developing. As always your feedback is really appreciated.

One of the most common questions we get at the Prism forums is of the type: “How do I execute my command when X happens?” (X not being a button being clicked ).  A sample of this type of question can be seen here, where a particular command needs to be executed whenever a textbox’s text changes. Our answer usually is that the user can create a command with an attached behavior. However, users are not always happy with this answer because of the complexity of having to create an attached behavior to hook up the command

For this reason, with the help of Matias Bonaventura, and Diego Poza’s Snippet Creator tool and this group of MSDN sites we created a code snippet that will enable developers to easily create this commands with attached behaviors.

Pre-Requirements

1. Download the Snippet Visual Studio installer and run the installer (the snippet is provided “AS IS” with no warranties and confers no rights).
2. The class where you run the snippet must have the following using statements:
   • The namespace of the Control that has the event your command will attach to.
   • Microsoft.Practices.Composite.Presentation.Commands. The snippet uses the CommandBehaviorBase<T> class of Prism-v2. MSDN site here.
   • System.Windows: For DependencyProperty class for example.
   • System.Windows.Input: Has the ICommand interface.

Using the snippet

Once you have performed the previous steps, you must take into account the following considerations:

• The snippet will create two classes. You will probably want to put the code it generates in a separate class file, dedicated to that particular command.
• The shortcut to insert the code snippet is: cmdbehavior. You must press TAB as any other code snippet requires to be inserted in your code.
• You must fill four replacements (the rectangles in green):
  1. CommandAction: A description of what the behavior handles. Example: TextChanged.
  2. BehaviorNameCommandBehavior: Replace with the name of the command behavior. Example: TextBoxTextChangedCommandBehavior.
  3. ControlType: The type of the control that has the events your command will attach to. Example: TextBox.
  4. EventName: The event of your control you will attach to.
• To bind the command in XAML, you simply need to add a definition to the namespace and then bind the command property of the $CommandAction$ class to the command in your ViewModel. Example:

  <Window x:Class=”WpfApplication1.Window1″
      …
      xmlns:cmd=”clr-namespace:Commanding.Modules.Order.Views”>
      <Grid>
          <TextBox cmd:TextChanged.Command=”{Binding Path=TextChangedCommand}”></TextBox>
      </Grid>
  </Window>

I hope this snippet is useful for you, and that you are able to save time and problems using it. I know I am .