How to implement Command with Tooltip in MVVM?

Most MVVM frameworks implement basic Command pat开发者_如何学Pythontern (for example DelegateCommand in PRISM), that uses Execute and CanExecute methods from ViewModel.

Hovewer, I often need to add a tooltip to the command. For example, I want to describe the purpose of a command or explain, why it has been disabled.

Currently my tooltips are independent, but this results in code duplication of style definitions.

Is there a way to integrate tooltips with the MVVM Command pattern?

Should I create my own Command class, or is it considered bad practice?

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I think your question is perfectly valid. I'm not aware of such a command. RoutedUICommand is the closest I can think of, but it's obviously routed (no good for MVVM) and only defines a Text property - no ToolTip.

As you've hinted, you could certainly define your own. Alternatively, you could define some kind of command registration service, whereby modules register ICommand implementations along with metadata about that command (including the tooltip).

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Why not just extend PRISM's 'Delegate Command' and add a ToolTip property?

public class DelegateCommandEx : DelegateCommand 
{
    public string ToolTip { get; set; }
}

I believe by default WPF commands don't have that property because a ToolTip doesn't have to be a string in WPF - it can be an object, a control, a group of controls, etc

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An ICommand is a way to bind to events raised by the UI in MVVM. It doesn't have a ToolTip property, and I don't see how this is useful as the command is acting as a handler and has no UI. Are you referring to a ToolTip specific Command in which case it does make sense?

Generally you would use the ToolTipService with WPF.