Do you need to write back to Sage 100?  If not, ODBC may be easier.

can you please share the ODBC example?

This is a VBScript example, but I assume you can translate the concept to C#.  (SOTAMAS90 is a user DSN created when logging in to Sage 100... the user / password / company code are set higher in the script, as are the Div / Vendor values).

None of this is specific to Sage 100, except for the connection string is the syntax for the Providex ODBC driver, so you should be able to Google to find C# examples of ODBC queries.

    strConn = "DSN=SOTAMAS90;UID=" & sSageUser & ";PWD=" & sSagePassword & ";company=" & sSageCompanyCode

    Set DBConn = CreateObject("ADODB.Connection")
    DBConn.open strConn    
    sSelect = "SELECT CheckEntryNo FROM AP_CheckHeader WHERE APDivisionNo= '" & sAPDiv & "' " & "AND VendorNo = '" & sVendor & "' "
    Set ReturnSet = CreateObject("ADODB.RecordSet")
    ReturnSet.Open sSelect, DBConn
    do until ReturnSet.EoF
       ...
       ReturnSet.MoveNext
    loop
    ReturnSet.Close
    DBConn.Close

Thanks Kevin

Thanks Kevin

How to get an Invoice and Line Item details? 

Can you please share the code or share the line item keywords?

I did get the Invoice No, Date and Shipping Address but I can not fetch the Line Items details?

One more thing, I have also got the PO & SO detail and Line Items details, but I am struggling in Invoice Line Items.

Can you please help me?

 oSS.InvokeMethod("nSetDate", "S/O", DateTime.Now.ToString("yyyyMMdd"));
            oSS.InvokeMethod("nSetModule", "S/O");

            int TaskID = (int)oSS.InvokeMethod("nLookupTask", "SO_Invoice_ui");
            int setProgramTest = (int)oSS.InvokeMethod("nSetProgram", TaskID);

            //we create two lists to store the line keys and quantities in.
            List<Invoice> invoiceList = new List<Invoice>();

            using (DispatchObject soObject = new DispatchObject(pvx.InvokeMethod("NewObject", "SO_Invoice_bus", oSS.GetObject())))
            {
                soObject.InvokeMethod("nMoveFirst");
                int sEOF = (int)soObject.GetProperty("nEOF");
                do
                {
                    var invoiceNo = soObject.GetDataObject("InvoiceNo$");

                    var invoice = new Invoice();
                    invoice.InvoiceNo = invoiceNo;
                    invoice.ShipToAddress1 = soObject.GetDataObject("ShipToAddress1$");
                    invoice.OrderDate = TextUtilities.ConvertDate(soObject.GetDataObject("InvoiceDate$"));

                    using (DispatchObject so_line = new DispatchObject(soObject.GetProperty("oLines")))
                    {
                        so_line.InvokeMethod("nMoveFirst");
                        int EOF = (int)so_line.GetProperty("nEOF");
                        do
                        {
                            var ItemCode = so_line.GetDataObject("ItemCode$");