howto delete rows from DataTable in C# with a filter?

Question

i have a DataTable with some rows, one of it is a ID (a string) and a System.DateTime. the other rows are not important now.

now i want to delete all the rows with the same ID that have an older DateTime as the newest.

is this possible?

here an example

• ID:123 Date:24.12.2010 ...
• ID:123 Date:23.12.2010 ...
• ID:123 Date:22.12.2010 ...

after this i only want:

• ID:123 Date:24.12.2010 ...

Answer 1

Try next

public void DeleteOldById(DataTable table, int id)
{
      var rows = table.Rows.Cast<DataRow>().Where(x => (int)x["ID"] == id);
      DateTime specifyDate = rows.Max(x => (DateTime)x["Date"])

      rows.Where(x =>(DateTime)x["Date"] < specifyDate).ToList().
           ForEach(x => x.Delete());
}


public void DeleteAllOldRows(DataTable table)
{
     var ids = table.Rows.Cast<DataRow>().Select(x => (int)x["ID"]).Distinct();
     foreach(int id in ids)
        DeleteOldById(table,id);
}