jquery调用webservice

1.给webserver加 [System.Web.Script.Services.ScriptService]标签
如:

[WebService(Namespace = "http://abc.org.cn/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.Web.Script.Services.ScriptService]
public class user : System.Web.Services.WebService
{
    [WebMethod]
    public bool CheckPwd(string name,string pwd)
    {
        return SchoolMIS.Sys.User.UserFactiory.GetUser().CheckPwd(name, pwd);
    }

}

2.js

   $(
        function()
        {
            function WebService(url,pars,callback)
            { 
                $.ajax
                ({ 
                    async :false,
                    data:pars, 
                    url: url, 
                    type: "POST", 
                    contentType: "application/json;utf-8", 
                    dataType:'json', 
                    cache: false, 
                    success: function(json){ 
                        callback(json);
                    },
                    beforeSend:function(xml)
                    { 
                        if(!pars) 
                        {
                            xml.setRequestHeader("Content-Type", "application/json;utf-8")
                        } 
                    },
                    error:function(xml,status)
                    { 
                        if(status=='error')
                        { 
                            try
                            { 
                                var json = eval('(' + xml.responseText + ')'); 
                                alert('Err:' + json.Message+'\n'+json.StackTrace); 
                            }
                            catch(e)
                            {} 
                        }
                        else
                        { 
                            alert('Err:' + status); 
                        } 
                    }                           
                });
            }
            
            $("#btnLogin").click
            (
                function()
                {
                   var n,p,r;
                    n=$("#txtUsername").val();
                    p=$("#txtPassword").val();
                    if(n.length==0 || p.length==0)
                    {
                        alert("Please input user name and password.");
                        $("#txtUsername")[0].focus();
                        if(n.length>0)
                            $("#txtPassword")[0].focus();
                         return false;
                    }
                    WebService(
                        "user.asmx/Login",
                        "{name:'" + n + "',pwd:'" + p + "'}",
                        function(jason)
                        {
                            if(!jason)
                            {
                                alert("User name or password error,please retry.");
                                $("#txtPassword")[0].focus();
                                r = false;
                            }
                            else
                            {
                                r = true;
                            }
                        }
                    );
                    if(r)
                        window.location.href="/MainForm.aspx";
                    return false;
                }            
            )
        }
    )