判字符串断输入非法字符

 //正则表达式，判断是否含有除了字母及数字外的其他字符
          Regex regex = new Regex(@"^[a-zA-z0-9]+$");       
         if (!regex.IsMatch(txtPsw.Value))
         {
             labMessage.Text = "密码包含非法字符";
             return;
         }
         //判断用户名是否是汉字、字母、数字组合
          char[] arrChar = txtUser.Value.ToCharArray(0, txtUser.Value.Trim().Length);
         foreach (char char1 in arrChar)
         {
             if (!char.IsLetterOrDigit(char1))
             {
                 labMessage.Text = "用户名包含非法字符";
                 return;
             }
         }