relaycommand

I develop an Universal app that uses the MVVM-Lght toolkit . On a page, I show a list of comments. I would like that an user could add a new comment, and edit or delete its existing comments. For adding new comment, I use an AppBarButton on the CommandBar and it works fine. For editing and deleting the existing comments, I would like to display a MenuFlyout that offers 2 items: " edit " and " delete ". I can display the MenuFlyout but nothing happens when I click on its items... Here is my concerned xaml code: <ListView x:Name="myCommentaires" ItemsSource="{Binding Comments}"

What are the performance implications of using the CanExecuteCommand of the ICommand object. Is the method executed over and over again? I need to iterate through a collection of about 200 objects based on which its decided whether the button bound to the Command should be enabled? Does the CanExecuteCommand get executed repeatedly which will make my application slow The ICommand interface is the following: public interface ICommand { // two methods bool CanExecute(object parameter); void Execute(object parameter); // one event event EventHandler CanExecuteChanged; } The CanExecuteChanged

How do you get event sender when using RelayCommand? This is one of those pain-in-the-%¤# answers where I don't actually answer your question, but instead lecture you about what you should be doing differently. So, sorry about that. Here goes: If you find yourself in a position where you need to get at the sender object in your viewmodel, then you should probably do something different. By referencing, say, a Button or a ListBox in your viewmodel you have made that viewmodel aware of UI concepts that it should not know anything about. My suggestion is to instead hook up to the event in the

So my first attempt did everything out of the code behind, and now I'm trying to refactor my code to use the MVVM pattern, following the guidance of the MVVM in the box information. I've created a viewmodel class to match my view class, and I'm moving the code out of the code behind into the viewmodel starting with the commands. My first snag is trying to implement a 'Close' button that closes the window if the data has not been modified. I've rigged up a CloseCommand to replace the 'onClick' method and all is good except for where the code tries to run this.Close() . Obviously, since the code

I got the following code from Josh Smith's MVVM tutorial . Can anyone provide a quick explanation of what this code actually does? public event EventHandler CanExecuteChanged { add { CommandManager.RequerySuggested += value; } remove { CommandManager.RequerySuggested -= value; } } I can't understand two things: what does the CanExecuteChanged event do? what does the CommandManager.RequerySuggested do? The above code is from the RelayCommand Class from here . CanExecuteChanged notifies any command sources (like a Button or MenuItem ) that are bound to that ICommand that the value returned by