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); }