Filtering duplicate records from datatable
public DataTable RemoveDuplicateRows(DataTable dTable, string colName)
{
Hashtable hTable = new Hashtable();
ArrayList duplicateList = new ArrayList();

foreach (DataRow drow in dTable.Rows)
{
if (hTable.Contains(drow[colName]))
duplicateList.Add(drow);
else
hTable.Add(drow[colName], string.Empty);
}

foreach (DataRow dRow in duplicateList)
dTable.Rows.Remove(dRow);

return dTable;
}