Date format issue in SAP C#.Net Conenction

I am using SAPConnectionManager with C# to connect to SAP system.
My connection is successfull but I am not getting any data from SAP.

Initially I suspect there might not be any data for parameter I am passing, but then I found the data is present in SAP system. My code for fetching data is as below.

   SapConnection con =newSapConnection();
   SAPSystemConnect sapCfg =newSAPSystemConnect();

   RfcDestinationManager.RegisterDestinationConfiguration(con);
   RfcDestination dest =RfcDestinationManager.GetDestination("NSP");
   RfcRepository repo = dest.Repository;

   IRfcFunction fReadTable =repo.CreateFunction("ZCAR_FI_AGF_GET_INVOICES");
   fReadTable.SetValue("IM_COMPANYCODE","0005");
   fReadTable.SetValue("IM_SAPCUSTOMER","19273");
   fReadTable.SetValue("IM_INVDATE_FROM","20130101");
   fReadTable.SetValue("IM_INVDATE_TO","20141231");

   fReadTable.Invoke(dest);
   IRfcTable objRfcTable = fReadTable[0].GetStructure().GetTable(0);

   if(objRfcTable.RowCount>0)
   {
   foreach(IRfcStructure row in objRfcTable)
   {
   object obj = row[0].GetValue();



I am always getting objRFCTable.RowCount as 0.

I suspect that there might be dateformat issue as date expected in SAP is yyyyMMdd but after passing 20130101 as a prameter when I go to quick watch on the request I see date getting passed as {IMPORT PARAMETER IM_INVDATE_FROM=2013-01-01}.

Can anyone help me with what is the issue. Is there any issue with dateformat or connection.

Thanks In Advance