使用ajax调用WebService函数

        string js;
        js = "";
        js += "function CallWebServices(){";
        js += "AutoComplete.GetLoginUserCount(onOK);";
        js += "}";
        js += "function onOK(returnData){";
        js += "$get('TextBox1').value=returnData;";
        js += "}";
        js = "<script>" + js + "</script>";
        ClientScript.RegisterStartupScript(typeof(string), "", js);
        Button1.Attributes.Add("onclick", "CallWebServices();");
        ScriptManager1.Services.Add(new System.Web.UI.ServiceReference("AutoComplete.asmx")); 

    [WebMethod]
    public string GetLoginUserCount()
    {
        string UserCount="0";
        UserCount =  Convert.ToString(SqlHelper.ExecuteScalar(ConfigurationSettings.AppSettings["connString"], "GetUsersLoginedCount")).Trim();//已登陆用户总数
        return UserCount;
    }