问当web服务试图与SharePoint 2007通信时，登录失败

EN

namespace WebService1
{
    /// <summary>
    /// Summary description for Service1
    /// </summary>
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
    // [System.Web.Script.Services.ScriptService]
    public class Service1 : System.Web.Services.WebService
    {
        [WebMethod]
        public string HelloWorld()
        {
            return "Hello World";
        }

        [WebMethod]
        public string ShowSPMyList()
        {
            string username = this.User.Identity.Name;
            return GetList();
        }

        private string GetList()
        {
            string resutl = "";
            SPSite siteCollection = new SPSite("http://localhost:89");
            using (SPWeb web = siteCollection.OpenWeb())
            {
                SPList mylist = web.Lists["MySPList"];
                SPQuery query = new SPQuery();
                query.Query = "<Where><Eq><FieldRef Name=\"AssignedTo\"/><Value Type=\"Text\">Ramprasad</Value></Eq></Where>";
                SPListItemCollection items = mylist.GetItems(query);
                foreach (SPListItem item in items)
                {
                    resutl = resutl + SPEncode.HtmlEncode(item["Title"].ToString());
                }
            }
            return resutl;
        }
    }
}