Question

I am just starting to use commanding with MVVM in an application. I’ve found a number of examples and have tried it both ways in my code. Some examples have the command binding in the xaml like so:

<CommandBinding Command="local:MainWindow.OpenRecentFile" 
                Executed="{Binding OpenRecentFile_Executed}" />
...
<MenuItem Header="{x:Static culture:TextResource.RecentFilesMenuItem}" 
          Command="local:MainWindow.RecentFilesCommand" >

With OpenRecentFile_Executed being a method in the ViewModel and a static ICommand like so:

 public static readonly ICommand OpenRecentFile = 
     new RoutedCommand("Open Recent", typeof(MainWindow));

I have also seen where there is a property on the ViewModel that is of type ICommand that is bound to in the View like so:

<MenuItem Header="Close Current File" 
          Command="{Binding CloseCurrentFileCommand}" 
          CommandParameter="{TemplateBinding DataContext}"/>

and in the ViewModel:

private ICommand closeCurrentFileCommand;
public ICommand CloseCurrentFileCommand
{
    get
    {
        if (closeCurrentFileCommand == null)
        {
            closeCurrentFileCommand = 
                new RelayCommand(param => this.CloseCurrentCedarFile(param));
        }
        return closeCurrentFileCommand;
    }
}

What are the benefits/drawbacks to each method?

Answer 1

It depends on your design. If you’re going for the quick approach – a Window with back-end code then declaring commands in XAML will probably save you some time and reduce the effort in the long run.

If you are going for a MVVM app then I would strongly suggest the binding to ICommand as commands in general are ways to manipulate your data (opening/saving/editing) and this should be defined in the ViewModel. Possibly more effort depends on the functionality but MVVM is a great way to go if you’re doing a larger application.

In the end both will work the same but it’s your design and approach which matter.