How to get duplicate records from DataTable and save in another DataTable using LINQ in ASP.Net

Hi iammann,

Below is the right way of finding the duplicate records and save them into new datatable.

C#

DataTable dt = new DataTable();
dt.Columns.Add("RowId");
dt.Columns.Add("FirstName");
dt.Columns.Add("LastName");
dt.Columns.Add("Quality");
dt.Rows.Add(1, "Tom", "Hilton", "ABC");
dt.Rows.Add(1, "Tom", "Hilton", "ABC");
dt.Rows.Add(3, "Test3", "Sample3", "AWR");
dt.Rows.Add(4, "Test4", "Sample4", "XYZ");
dt.Rows.Add(5, "Test5", "Sample5", "BCA");

DataTable resultTable = new DataTable();
resultTable.Columns.Add(new DataColumn("RowId"));
resultTable.Columns.Add(new DataColumn("FirstName"));
resultTable.Columns.Add(new DataColumn("LastName"));
resultTable.Columns.Add(new DataColumn("Quality"));

var result = from c in dt.AsEnumerable()
                group c by new
                {
                    RowId = c.Field<string>("RowId"),   //column names for checking duplicate values.
                    FirstName = c.Field<string>("FirstName"),
                    LastName = c.Field<string>("LastName"),
                    Quality = c.Field<string>("Quality")
                } into g
                where g.Count() > 1
                select new
                {
                    g.Key.RowId,
                    g.Key.FirstName,
                    g.Key.LastName,
                    g.Key.Quality
                };

for (int i = 0; i < result.ToList().Count; i++)
{
    var item = result.ToList()[i];
    resultTable.Rows.Add(item.RowId, item.FirstName, item.LastName, item.Quality);
}