Question

I want to select those gesellschaft_id’s who have duplicates. I used the code below. this is selecting distinct gesellschaft_id. How to write the select expression to select that row, which rows, gesellschaft_id have more values in the datatable?

foreach (DataRow dr1 in table1.Rows)
        {
            DataRow[] drDup = table2.Select("('" + dr1[0].ToString() + "' = gesellschaft_id ) AND Count(gesellschaft_id)>1");

        }

Answer 1

This will give you the DataRows which have a gesellschaft_id which exists in more than one row:

var rowsWithADuplicateGesellschaftId = table1.Rows
    .Cast<DataRow>()
    .GroupBy(row => row["gesellschaft_id"])
    .Where(group => group.Count() > 1)
    .ToArray();