AJAX之xmlHttp

<script type="text/javascript" language="javascript">
        <!--
        //以XML求取数据
        function XmlPost(theEmail)
        {
　　        var webFileUrl = "../User/CheckUser.aspx?LogonName=" + theEmail;
　　        var result = "";
　　        　　       
　　        if (window.ActiveXObject) {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            else if (window.XMLHttpRequest) {
            xmlHttp = new XMLHttpRequest();
            }

　　        //var xmlHttp = new ActiveXObject("MSXML2.XMLHTTP");
　　        xmlHttp.open("POST", webFileUrl, false);
　　        xmlHttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded");   
　　        xmlHttp.send("");　　    　　       
　　               
            xmlHttp.onreadystatechange=function()
            {
                if (xmlHttp.readyState==4)
                {
                    result = xmlHttp.responseText;
                }
            }
            if(xmlHttp.status!=200)
            {
                alert ('网络故障(xmlHttp.status='+xmlHttp.status+')，请稍后再试！');
            }
               
            result = xmlHttp.responseText;　
　　        result = result.substring(0,result.indexOf("?EX"));
　　       
　　        if(result != "false")
　　        {　　　　       
　　　　        return true;
　　        }
　　        else
　　        {
　　　　        return false;
　　        }
        }
        //-->
    </script>''' <summary>
''' 检测用户是否存在<文件名：../User/CheckUser.aspx>
''' </summary>
''' <remarks>Created by dzh @2006/06/27 18:22</remarks>
Partial Class Web_User_CheckUser
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If Request.QueryString("LogonName") Is Nothing Then
            Response.Write("false" + "?EX")
            Response.End()
            Exit Sub
        End If

        If (New EasyClick.EasyBusiness.UserBusiness).GetUserByLogonName(Request.QueryString("LogonName").ToString) Is Nothing Then
            Response.Write("false" + "?EX")
            Response.End()
            Exit Sub
        Else
            Response.Write("true" + "?EX")
            Response.End()
            Exit Sub
        End If
    End Sub
End Class