Crystal Report：无法从数据库加载

Question

我正在使用此代码，但却给了我这个错误：

  

无法从数据库中检索数据。详细信息：[数据库供应商代码：201]

public JsonResult ReportCertificateOfEmployment(int EmployeeId, int SigId, string SigPosition)
    {
        string Userkey = "gHeOai6bFzWskyUxX2ivq4+pJ7ALwbzwF55dZvy/23BrHAfvDVj7mg  ";
        string PassKey = "lLAHwegN8zdS7mIZyZZj+EmzlkUXkvEYxLvgAYjuBVtU8sw6wKXy2g  ";

        string rptlogin = ConfigurationManager.AppSettings.Get("rptlogin");
        string rptPassword = ConfigurationManager.AppSettings.Get("rptPassword");

        MemoryStream oStream;
        CertificateOfEmployment rpt = new CertificateOfEmployment();
        rpt.Refresh();
        rpt.SetDatabaseLogon(rptlogin, rptPassword);
        rpt.SetParameterValue(0, EmployeeId);
        rpt.SetParameterValue(1, SigId);
        rpt.SetParameterValue(2, SigPosition);
        rpt.SetParameterValue(3, DateTime.Now);

       oStream = (MemoryStream)rpt.ExportToStream(CrystalDecisions.Shared.ExportFormatType.PortableDocFormat); --------- this gives me an error

      // extract only the fielname
        string filename = Convert.ToString((DateTime.Now.Month) + Convert.ToString(DateTime.Now.Day) + Convert.ToString(DateTime.Now.Year) + Convert.ToString(DateTime.Now.Hour) + Convert.ToString(DateTime.Now.Minute) + Convert.ToString(DateTime.Now.Second) + Convert.ToString(DateTime.Now.Millisecond)) + "BarangayClearance";
        var len = oStream.Length;
        // store the file inside ~/App_Data/uploads folder
        // var path = Path.Combine(Server.MapPath("~/Content/Images"), fileName);
        // file.SaveAs(path);

        FileTransferServiceClient client2 = new FileTransferServiceClient();
        RemoteFileInfo rmi = new RemoteFileInfo();
        DateTime dt = DateTime.Now;
        // upload file using webservice
        DownloadRequest dr = new DownloadRequest();
        //web service method to upload a file and return the unique id of the newly uploaded file
        string fId = client2.UploadFileGetId("", filename, len, PassKey, Userkey, oStream);
        //Instantiate the object Img which is a table in the database server of the application
        //Download file using web service;
        //DownloadFile in Refence.cs has been edited to return a RemoteFileInfo Class
        //before, the return type of DownloadFile method was a  Stream type
        JsonResult result = new JsonResult();
        result.Data = new
        {
            fileId = fId,
            filename = filename
        }; 

        rpt.Close();
        rpt.Dispose();

        var arr = oStream.ToArray();

        oStream.Close();
        oStream.Dispose();

        result.JsonRequestBehavior = JsonRequestBehavior.AllowGet;
        return result;
    }