Bapi_Salesorder_Getlist return no items

Question

When calling the Bapi_Salesorder_Getlist from .NET Connector but got no items return.
I can browse the order for customer 1012 in SAPGUI.
If the problem is caused by the searching parameters?
Please check the code for me.
Thanks!
     Orders.SAPProxyOrders proxyorders= new Orders.SAPProxyOrders(cs);
     // call the RFM method on the proxy
     Orders.BAPIRETURN Return0=new Orders.BAPIRETURN();
     Orders.BAPIORDERSTable Sales_Orders=new Orders.BAPIORDERSTable();
     try
          proxyorders.Bapi_Salesorder_Getlist("1012", "", "", "", "", "", "", "*", out Return0, ref Sales_Orders);
     catch(SAP.Connector.RfcCommunicationException exp)
          MessageBox.Show(exp.Message);
          return;
     catch(Exception exp)
          MessageBox.Show(exp.Message);
          return;
               this.labelResultNumber.Text=Sales_Orders.Count.ToString();

Answer 1

Thanks.
Your hint is very helpful.
Bapi_Customer_GetDetail can read single customer by giving customernumber (Knnum)
Bapi_Order_GetStatus can also read a single order by giving order number.
But When calling Bapi_Order_GetList or Bapi_Customer_GetList, it return no Rows.
The BAPIREAUT.Number is 748, its Message said "No cusomter was found by giving criteria.
I still suspect the searching parameters is wrong.
The requirement is to list all the orders of a customer.
Or could you give me such code directyly.
Thanks a lot