<asp:TextBox ID="tbLink" runat="server" MaxLength="32" style="ime-mode:disabled;"></asp:TextBox>

//原生JavaScript全角转换为半角函数 
function ToCDB(str){
  var result = '';
  for(var i=0; i < str.length; i++){
    code = str.charCodeAt(i);
    if(code >= 65281 && code <= 65374){
      result += String.fromCharCode(str.charCodeAt(i) - 65248);
    }else if (code == 12288){
      result += String.fromCharCode(str.charCodeAt(i) - 12288 + 32);
    }else{
      result += str.charAt(i);
    }
  }
 return result;
}

 　　　　/// <summary>
        /// 转换为半角字符串
        /// </summary>
        /// <param name="text"></param>
        /// <returns></returns>
        public static string ConvertToHalf(string text) 
        {
            char[] c = text.ToCharArray();

            for (int i = 0; i < c.Length; i++)
            {
                byte[] b = System.Text.Encoding.Unicode.GetBytes(c, i, 1);
                if (b.Length == 2)
                {
                    if (b[1] == 255)
                    {
                        b[0] = (byte)(b[0] + 32);
                        b[1] = 0;
                        c[i] = System.Text.Encoding.Unicode.GetChars(b)[0];
                    }
                }
            }
            return new string(c);
        }