protected override bool OnCanExecute(object parameter) { if (parameter is IUserDescriptor userDescriptor) { return(UserUtility.CanSendMessage(this.authenticator, userDescriptor)); } else if (parameter is IDomainMemberDescriptor domainMemberDescriptor) { return(DomainMemberUtility.CanSendMessage(this.authenticator, domainMemberDescriptor)); } return(false); }