Hi nabilabolo,

Refer below code.

C#

DataTable dt = new DataTable();
dt.Columns.AddRange(new DataColumn[]
{
    new DataColumn("Date",typeof(DateTime)),
    new DataColumn("Data",typeof(string))
});
dt.Rows.Add("2021-01-01", "A");
dt.Rows.Add("2021-01-26", "A");
dt.Rows.Add("2020-12-21", "B");

var result = dt.AsEnumerable().OrderByDescending(x=>x["Date"]).GroupBy(x => x["Data"]).Select(x => x.First()).ToList();

VB.Net

Dim dt As DataTable = New DataTable()
dt.Columns.AddRange(New DataColumn() {New DataColumn("Date", GetType(DateTime)), New DataColumn("Data", GetType(String))})
dt.Rows.Add("2021-01-01", "A")
dt.Rows.Add("2021-01-26", "A")
dt.Rows.Add("2020-12-21", "B")
Dim result = dt.AsEnumerable().OrderByDescending(Function(x) x("Date")).GroupBy(Function(x) x("Data")).Select(Function(x) x.First()).ToList()