void btnPassword_Click(object sender, RoutedEventArgs e)
 {
     metadata_password = this.xtnTableField.SelectedMetaData;
     if (null == metadata_password)
     {
         Wrapper.ShowDialog("请选择要关联的密码字段!");
     }
     _PasswordField = metadata_password.column_name;
 }
 void btnUsername_Click(object sender, RoutedEventArgs e)
 {
     metadata_username = this.xtnTableField.SelectedMetaData;
     if (null == metadata_username)
     {
         Wrapper.ShowDialog("请选择要关联的用户名字段!");
     }
     _UserField = metadata_username.column_name;
 }