<script type="text/javascript">
    $(function () { 
      $("#txtemail").blur(function () {
        $.ajax({
          type: "post",
          url: "reg.ashx?email=" + $.trim($("#txtemail").val()) + "&d=" + (+new date()),
          success: function (data) {
            var vcount = parseint(data);
            if (vcount == 0) {
              alert("邮箱可以使用");
            }
            else {
              alert("邮箱已经被占用");
            }
          }
        });
      });
      $("#checkpwd").blur(function () {
        return checkpwd();
      });
    });
    function checkpwd()
    {
      var bcheck = true;
      if ($.trim($("#pwd").val()) != $.trim($("#checkpwd").val()))
      {
        alert("两次密码输入不一致");
        bcheck = false;
      }
      return bcheck;
    }
  </script>

using system;
using system.collections.generic;
using system.linq;
using system.web;
namespace webt1.ti.html2
{
  /// <summary>
  /// reg 的摘要说明
  /// </summary>
  public class reg : ihttphandler
  {
    public void processrequest(httpcontext context)
    {
      if (context.request["email"] != null)
      {
        string stremail = context.request["email"];
        list<usermodel> lstuser = dataservice.getuserlist();
        var v = lstuser.where(p => p.email == stremail);
        int icount = 0;
        if (v.count() > 0)
        {
          icount = 1;
        }
        context.response.contenttype = "text/plain";
        context.response.write(icount.tostring());
      }
    }
    public bool isreusable
    {
      get
      {
        return false;
      }
    }
  }
  public class dataservice
  {
    /// <summary>
    /// 模拟已注册用户数据
    /// </summary>
    public static list<usermodel> getuserlist()
    {
      var list = new list<usermodel>();
      list.add(new usermodel() { email = "t1@demo.com" });
      list.add(new usermodel() { email = "t2@demo.com" });
      list.add(new usermodel() { email = "t3@demo.com" });
      list.add(new usermodel() { email = "t4@demo.com" });
      list.add(new usermodel() { email = "t5@demo.com" });
      return list;
    }
  }
  public class usermodel
  {
    public string email { get; set; }
  }
}