Passing a parameter to RelayCommand - wpf

Question

I'm experimenting with the ICommand and RelayCommand constructs. Looking around, I've put together the following code:
public class RelayCommand : ICommand
{
private Action<object> _executeMethod;
private Func<object, bool> _canExecuteMethod;
public RelayCommand(Action<object> ExecuteMethod, Func<object, bool> CanExecuteMethod)
{
_executeMethod = ExecuteMethod;
_canExecuteMethod = CanExecuteMethod;
}
public event EventHandler CanExecuteChanged;
public bool CanExecute(object parameter)
{
if (_canExecuteMethod != null)
{
return _canExecuteMethod(parameter);
}
else
{
return false;
}
}
public void Execute(object parameter)
{
if (_executeMethod != null)
{
_executeMethod(parameter);
}
}
}
and I use all this from my main code as follows:
private bool CanExecuteMyCommand (object parameter) { /* do something here */ }
private void ExecuteMyCommand(object parameter) { /* do something here */ }
private ICommand _execMyCmd;
public ICommand ExecMyCmd
{
get { return _execMyCmd; }
set { _execMyCmd = value; }
}
ExecMyCmd = new RelayCommand(ExecuteMyCommand, CanExecuteMyCommand);
This works fine, but one thing I've not been able to find is how to pass a parameter to ExecuteMyCommand. I've tried something like:
ExecMyCmd = new RelayCommand(ExecuteMyCommand ("foo"), CanExecuteMyCommand);
but Visual Studio shows an error. Can anybody shed some light on this?
Thanks
Gianni

Answer 1

Command parameters are typically passed by the control which binds to the command. Here is an example:
<Button x:Name="btn"
Content="Click"
Command="{Binding ExecMyCmd}"
CommandParameter="{Binding ElementName=btn, Path=Content}"/>
This will pass the content of the button, which is "Click", as parameter. Note that this is an example, so you could pass what ever you want here.