在windows服务中打开spweb

我想检查SharePoint库中的文档属性。请告诉我如何在windows服务中打开SharePoint网站。我在windows服务中使用以下代码，它给出"站点未发现错误"。

SPSite spSite = new SPSite("http://xyz/sites/abc");

Detail Error is，

System.IO.FileNotFoundException: The Web application at http://xyz/sites/abc could not be found. Verify that you have typed the URL correctly. If the URL should be serving existing content, the system administrator may need to add a new request URL mapping to the intended application.
   at Microsoft.SharePoint.SPSite..ctor(SPFarm farm, Uri requestUri, Boolean contextSite, SPUserToken userToken)
   at Microsoft.SharePoint.SPSite..ctor(String requestUrl)
   at SSP_DL_notify_service.Service1.GetMail(Object sender, ElapsedEventArgs args) in C:'Users'pqr'Documents'Visual Studio 2010'Projects'SSP_DL_notify_service'SSP_DL_notify_service'Service1.cs:line 54