Sub CSVR()

        Dim tbl_csv As New DataTable
        Dim data() As String
        Dim separator As String = ","

        cmb_clmn.Items.Clear()
        For i = 0 To DataGridView1.Columns.Count - 1
            If DataGridView1.Columns(i).HeaderText.Contains("Lastseen") Then
                tbl_csv.Columns.Add(DataGridView1.Columns.Item(i).HeaderText, GetType(Date))
            Else
                tbl_csv.Columns.Add(DataGridView1.Columns.Item(i).HeaderText)
            End If
            'tbl_csv.Columns(i).Caption = DataGridView1.Columns.Item(i).HeaderText
            cmb_clmn.Items.Add(DataGridView1.Columns.Item(i).HeaderText)
        Next

        Try
            Using csv As New IO.StreamReader(lbl_pth.Text)
                Do While csv.EndOfStream = False
                    data = Split(csv.ReadLine(), separator)
                    tbl_csv.Rows.Add(data)
                Loop
            End Using

            DataGridView1.Columns("Lastseen").DefaultCellStyle.Format = "d"
            'tbl_csv.Columns("Lastseen").DateTimeMode = DataSetDateTime.UnspecifiedLocal
            'tbl_csv.Columns("Lastseen").DataType = GetType(DateTime)
            'tbl_csv.Columns.Item("Lastseen") = DateTime.Parse(tbl_csv.Columns.Item("Lastseen"))
            DataGridView1.DataSource = Nothing
            DataGridView1.Columns.Clear()
            DataGridView1.DataSource = tbl_csv

            For i As Integer = 0 To tbl_csv.Columns.Count - 1
               ' DataGridView1.Columns.Item(i).Visible = False
                'DataGridView1.Columns.Item(i).ReadOnly = True
                'DataGridView1.Columns.Item(i).SortMode = DataGridViewColumnSortMode.Automatic
            Next
       Catch ex As Exception
            '///////////////////////////////////////////////
            MsgBox(ex.Message, MsgBoxStyle.Critical, "erR0r in CSVR")
        End Try
    End Sub

    Public Shared Function DatTime(ByVal txtDate As String)
        Dim tempDate As DateTime
        DateTime.TryParseExact(txtDate, "dd/MM/yyyy", System.Globalization.CultureInfo.CurrentCulture, Globalization.DateTimeStyles.None, tempDate)
        Return tempDate
    End Function

    Public Function RemoveDuplicateRows(ByVal dTable As DataTable, ByVal colName As String) 'As DataTable
        ' On Error Resume .
        Dim dict As New Dictionary(Of String, DataRow)
        Dim dtb As New DataTable

        For Each dtRow As DataRow In dTable.Rows
            Dim key As String = dtRow("PublishingPoint") + "," + dtRow("Username") + "," + dtRow("IP") + "," + dtRow("Status") + "," + dtRow("Req URL") '+ ","  + dtRow("Last seen")
            Dim dictRow As DataRow = Nothing
            If dict.TryGetValue(key, dictRow) Then
                'check and update date
                'you can skip this part, if your data is sorted
                If DatTime(dtRow(colName)) > DatTime(dictRow(colName)) Then
                    dictRow(colName) = DatTime(dtRow(colName))

                End If
            Else
                dict.Add(key, dictRow)
            End If
        Next

        Return dict.Values.ToArray()

    End Function

 Private Sub chb_remdup_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles chb_remdup.CheckedChanged

        DataGridView1.DataSource = RemoveDuplicateRows(DataGridView1.DataSource, "Lastseen")

    End Sub






My *.csv Content:

-,AST-VM2003\Administrator,192.168.137.221,2,file:--C:\WMPub\WMRoot\industrial.wmv,10-10-2014
-,AST-VM2003\Administrator,192.168.137.221,2,file:--C:\WMPub\WMRoot\industrial.wmv,11-10-2014
-,AST-VM2003\Administrator,192.168.137.221,2,file:--C:\WMPub\WMRoot\industrial.wmv,12-30-2014
-,AST-VM2003\Administrator,192.168.137.222,2,file:--C:\WMPub\WMRoot\industrial.wmv,12-10-2014
-,AST-VM2003\Administrator,192.168.137.222,2,file:--C:\WMPub\WMRoot\industrial.wmv,12-11-2014
-,AST-VM2003\Administrator,192.168.137.222,2,file:--C:\WMPub\WMRoot\industrial.wmv,12-12-2014