Still getting "The report filename was empty" error

Question

I tried re-opening this earlier discussion...
"The report filename was empty" rears its ugly head again
... after this error came back; we moved our data source and I had to switch from using the viewer SDK to the engine SDK. Since I haven't seen any replies, I thought I should try creating a new discussion thread. It seems that my report which has parameters will work with the engine/ReportDocument code, but the one without parameters produces the above error. The sample code is in the other thread so I won't re-copy it here unless advised to do so. I really need to get this resolved so any guidance is greatly appreciated.
- Robert -

Answer 1

In the previous thread I attempted to provide some sample code I used for my test. Here's the meat of it, which gets called during the Page_Load event:
        private void ConfigureCrystalWithDbOverride(string ReportFile)
            ConnectionInfo crConn = CreateConnectionInfo();
            ReportDocument rptDoc = new ReportDocument();
            rptDoc.Load(Server.MapPath(ReportFile));
            Tables crTables = rptDoc.Database.Tables;
            foreach (CrystalDecisions.CrystalReports.Engine.Table tbl in crTables)
                tbl.LogOnInfo.ConnectionInfo = crConn;
                tbl.ApplyLogOnInfo(tbl.LogOnInfo);
            // If the selected report has parameters, clear them out first to ensure the viewer prompts each
            // time for user input.
            if (this.crviewer1.ParameterFieldInfo.Count > 0)
                this.crviewer1.ParameterFieldInfo.Clear();
            // Get database logon info from web.config
            Session["DynamicReport"] = rptDoc;   // Save to Session object which will be needed during subsequent postbacks
            DisplayReportInViewer(rptDoc);
        private ConnectionInfo CreateConnectionInfo()
            ConnectionInfo crInfo = new ConnectionInfo();
            string conn = ConfigurationManager.ConnectionStrings["MAS_ConnectionString"].ConnectionString;
            SqlConnection sqlConn = new SqlConnection(conn);
            crInfo.ServerName = sqlConn.DataSource;
            crInfo.DatabaseName = sqlConn.Database;
            crInfo.IntegratedSecurity = true;
            return crInfo;
        private void DisplayReportInViewer(ReportDocument rptDoc)
            this.crviewer1.ReportSource = rptDoc;
            this.crviewer1.RefreshReport();
I should probably point out one other change from the original environment. Originally we were connecting with SQL authentication and now we're using integrated security. Not sure whether that's relevant to this particular issue, but wanted to make sure it was known.