Linq Identify Duplicate Rows only based on 2 columns

Hi Team,

I want to identify if duplicate rows found in a datatable

using the below linq to find duplicate rows but it loops all the columns to find duplicate rows but want to check if duplicate rows found on CreditDebit and Invoice Number column

(From r1 In TransactionData.AsEnumerable()
Let cnt = TransactionData.AsEnumerable.Where(Function (r2) r1.ItemArray.SequenceEqual(r2.ItemArray)).Count
Where cnt > 1
Select r1).toList


Want to check if Multiple Credit is available, if yes then need to check if InvoiceNumber is same or different for credit rows.

have a look here:
FindDupsUniquesFirstFromGroup_By2Cols.xaml (12.3 KB)