Copy rows from one Datatable to another DataTable?

foreach (DataRow dr in dataTable1.Rows) {
    if (/* some condition */)
        dataTable2.Rows.Add(dr.ItemArray);
}

The above example assumes that dataTable1 and dataTable2 have the same number, type and order of columns.

Try This

    String matchString="ID0001"//assuming we have to find rows having key=ID0001
    DataTable dtTarget = new DataTable();
    dtTarget = dtSource.Clone();
    DataRow[] rowsToCopy;
    rowsToCopy = dtSource.Select("key='" + matchString + "'");
    foreach (DataRow temp in rowsToCopy)
    {
        dtTarget.ImportRow(temp);
    }

Copy Specified Rows from Table to another

// here dttablenew is a new Table  and dttableOld is table Which having the data 

dttableNew  = dttableOld.Clone();  

foreach (DataRow drtableOld in dttableOld.Rows)
{
   if (/*put some Condition */)
   {
      dtTableNew.ImportRow(drtableOld);
   }
}

Check this out, you may like it (previously, please, clone table1 to table2):

table1.AsEnumerable().Take(recodCount).CopyToDataTable(table2,LoadOption.OverwriteChanges);

Or:

table1.AsEnumerable().Where ( yourcondition  ) .CopyToDataTable(table2,LoadOption.OverwriteChanges);