Inventory Transfer Transaction Not Getting Rollbacked!

Hi

I am trying to rollback the Inventory Transfer Transaction from my code yet the entry is getting saved. I am pasting my code below. Any help will be appreciated.

private string Create_InvTransfer_BeforeSave(SAPbouiCOM.Form oform, string Type, string Warehouse, int QCDocentry)
{


    string DisplayError = "";


    try
    {


        oEdit1 = (SAPbouiCOM.EditText)oform.Items.Item("txtDocEnt").Specific;
        oEdit2 = (SAPbouiCOM.EditText)oform.Items.Item("txtDocNum").Specific;
        oComboBox1 = (SAPbouiCOM.ComboBox)oform.Items.Item("cmbPrdCd").Specific;
        oEdit4 = (SAPbouiCOM.EditText)oform.Items.Item("txtInspQty").Specific;


        if (Type == "Approve")
        {
            oEdit3 = (SAPbouiCOM.EditText)oform.Items.Item("txtApprQty").Specific;
            oComboBox = (SAPbouiCOM.ComboBox)oform.Items.Item("cmbAppWH").Specific;
        }
        else if (Type == "Sample")
        {
            oEdit3 = (SAPbouiCOM.EditText)oform.Items.Item("txtQcSmp").Specific;
            oComboBox = (SAPbouiCOM.ComboBox)oform.Items.Item("cmbSamWH").Specific;
        }
        else if (Type == "Reject")
        {
            oEdit3 = (SAPbouiCOM.EditText)oform.Items.Item("txtManRej").Specific;
            oComboBox = (SAPbouiCOM.ComboBox)oform.Items.Item("cmbRejWH").Specific;
        }


        


        int RetVal = 0;
        string ErrMsg = "";
        int ErrCode = 0;
        oCompany.StartTransaction();
        SAPbobsCOM.StockTransfer oInvTrans = default(SAPbobsCOM.StockTransfer);
        oInvTrans = (SAPbobsCOM.StockTransfer)oCompany.GetBusinessObject(SAPbobsCOM.BoObjectTypes.oStockTransfer);


        oInvTrans.DocDate = DateTime.Now;
        oInvTrans.FromWarehouse = Warehouse;
        oInvTrans.ToWarehouse = oComboBox.Value.Trim();


        oInvTrans.Lines.SetCurrentLine(0);
        oInvTrans.Lines.ItemCode = oComboBox1.Value.Trim();
        oInvTrans.Lines.FromWarehouseCode = Warehouse;
        oInvTrans.Lines.WarehouseCode = oComboBox.Value.Trim();
        oInvTrans.Lines.Quantity = double.Parse (oEdit3.Value);


        oInvTrans.Lines.UserFields.Fields.Item("U_DocEntry").Value = QCDocentry;
        if (Type == "Approve")
        {
            oInvTrans.Lines.UserFields.Fields.Item("U_ObjType").Value = "Is_OnlQc " + Type;
        }
        else if (Type == "Sample")
        {
            oInvTrans.Lines.UserFields.Fields.Item("U_ObjType").Value = "Is_OnlQc " + Type;
        }
        else if (Type == "Reject")
        {
            oInvTrans.Lines.UserFields.Fields.Item("U_ObjType").Value = "Is_OnlQc " + Type;
        }
        oInvTrans.Lines.UserFields.Fields.Item("U_InspQty").Value = double.Parse (oEdit4.Value);


        oInvTrans.Lines.Add();
        RetVal = oInvTrans.Add();
        if (RetVal != 0)
        {
            oCompany.GetLastError(out ErrCode, out  ErrMsg);
            DisplayError = ErrMsg;
            return DisplayError;


        }
        else
        {
            oCompany.EndTransaction(BoWfTransOpt.wf_RollBack);
            return DisplayError;


        }


    }
    catch (Exception ex)
    {
        oCompany.EndTransaction(BoWfTransOpt.wf_RollBack);
        DisplayError = ex.ToString ();
        return DisplayError;
    }
}