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 ...

Stecya · Accepted Answer · 2011-05-16 14:57:31Z

7

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);
}

edited May 16, 2011 at 14:57

answered May 16, 2011 at 14:22

Stecya

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5 Comments

hansgiller Over a year ago

is it not possible with the select method?

hansgiller Over a year ago

i dont know a specifyDate before

Stecya Over a year ago

See my edit. You can calculate specifyDate before executing query

hansgiller Over a year ago

now the second thing is, that you get only one max, but i have several ID's and each ID should after the select statement only exists one time tihe the newest date

hansgiller Over a year ago

all fine but he dont get the specifyDate (changes Date to Time) my definition looks like: time.ColumnName = "Time"; time.DataType = Type.GetType("System.DateTime"); data.Columns.Add(time);

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