How to add Command Args?

Heyho, I am currently working on something and trying to add
a command which should be like this /grab <player> .. the selected player should return then his UserID and print it back to the BasePlayer
I kind of fail to add the second argument to get the <player> working. 

 

It looks like this currently:

[ChatCommand("grab")]
private void grabCMD(BasePlayer player, string command, string[] args)
{
var Active = BasePlayer.activePlayerList as List<BasePlayer>;


if (!permission.UserHasPermission(player.UserIDString, perm))
{
  // Do something
}
else
{

foreach (BasePlayer plyer in Active)
{ 
   // Function

}

}

}
args is string[], that means that first string in the list is arg wich are first (args[0]), etc....
switch (args[0]) // argument #1
{
                case "pos":
                    // action                        
                    break;
                    
                    
                case "player":
                    // action
                    break;
                    
                default:
                    // action
                    break;
}