public override bool CheckPreconditions()
 {
     if (!base.CheckPreconditions())
     {
         return(false);
     }
     if (!_persistance.GroupExists(Mapping[AddGroupChannelArguments.Group]))
     {
         Messages.Add(string.Format("Groupname {0} doesn't exists.", Mapping[AddGroupChannelArguments.Group]));
         return(false);
     }
     if (_persistance.GroupChannelExists(Mapping[AddGroupChannelArguments.Channel]))
     {
         Messages.Add(string.Format("Channel {0} already exists.", Mapping[AddGroupChannelArguments.Channel]));
         return(false);
     }
     return(true);
 }