UI Commands details

MSDN says that one can create a custom command in 2 ways: either by declaring a class that implements ICommand or by "using" RoutedCommand or RouterUICommand classes (that derive from Command).

Question 1: what is the difference between those 2 approaches? MSDN says that first one gives you more flexibility, but what exactly?

Let`s use the second approach. To define a custom command I should use the following code:

public static RoutedUICommand DownloadCommand = new RoutedUICommand("Download data", "DownloadCommand", typeof(DownloadCommandWrapper), new InputGestureCollection(new InputGesture[] { new KeyGesture(Key.F2, ModifierKeys.None, "Download data") }));

That`s ok. I could call this command eg. from a button by assigning this command under 'Command' property of a button. But how could I call it from a control that does not expose such property? For example, I would like to call this command after user clicks the Image.

Thank you in advance for help