After installing SAPActivity as a prerequisite.
Import SAP.Middleware.Connector into your namespace.
//Connection
SAP.Middleware.Connector.RfcConfigParameters cfgParams = new SAP.Middleware.Connector.RfcConfigParameters();
cfgParams.Add("NAME", "Test");
cfgParams.Add("ASHOST", "XXXXXXX");
cfgParams.Add("CLIENT", "XXX");
cfgParams.Add("USER", "XXXXX");
cfgParams.Add("PASSWD", "XXXSX");
cfgParams.Add("LANGUAGE", "XX");
Destination = SAP.Middleware.Connector.RfcDestinationManager.GetDestination(cfgParams);
RfcFunction_SalesOrder = Destination.Repository.CreateFunction("BAPI_SALESORDER_CREATEFROMDAT2");
RfcFunction_Commit = Destination.Repository.CreateFunction("BAPI_TRANSACTION_COMMIT");
/*
//Fill in the data
SAP.Middleware.Connector.IRfcTable RfcTable = RfcFunction_SalesOrder.GetTable("ORDER_ITEMS_IN");
RfcTable.Append();
RfcTable.SetValue("ORDER_ITEMS_IN",[TableData]);
SAP.Middleware.Connector.IRfcStructure RfcStructure = RfcFunction_SalesOrder.GetStructure("ORDER_HEADER_IN");
RfcStructure.SetValue("ORDER_HEADER_IN",[StructureData]);
RfcFunction_SalesOrder.SetValue([ValueNAME],XX)
*/
//BAPIExcute
SAP.Middleware.Connector.RfcSessionManager.BeginContext(Destination);
RfcFunction_SalesOrder.Invoke(Destination);
RfcFunction_Commit.Invoke(Destination);
SAP.Middleware.Connector.RfcSessionManager.EndContext(Destination);