Is it okay to use ICommand in view-model

Question

Most of the WPF mvvm applications, we are using ICommand in the view-model. But it is referring to System.Windows.Input. so the view-model is now tightly couple with System.Windows.Input namespace. according to my understanding view-model should be able to use in normal C# winform application or asp.net application.

Normally we are using following code lines to the command with RelayCommand implementation.

private RelayCommand testCommand;// or private ICommand testCommand;

public ICommand TestCommand
{
    get
    {
        return testCommand ?? 
            (testCommand = new RelayCommand(param => Test()));
    }
}

public void Test()
{

}

What i feel is we need to remove all the ICommand and use RelayCommand instead. So we can eliminate the System.Windows namespace from the view-model. so final code will looks like this,

private RelayCommand testCommand;

public RelayCommand TestCommand
{
    get
    {
        return testCommand ?? 
            (testCommand = new RelayCommand(param => Test()));
    }
}

public void Test()
{

}

Any suggestions on this approach? or is there any way to eliminate the System.Windows namespace from the view-model?

Answer 1

Any suggestions on this approach?

This still doesn't decouple you from System.Windows.Input as RelayCommand still must implement ICommand, even if it's indirectly implementing it.

Implementing ICommand within the ViewModel is one of those things that tends to be required in order to be pragmatic. Ideally, ICommand (or a similar interface) would have been implemented in a namespace that wasn't XAML specific. That being said, it is supported directly within the Portable Class Libraries, so it is not tied to a specific framework (WPF, Silverlight, Phone, etc) as much as XAML in general.