Прочесть и обработать текстовый файл "log.txt" в котором несколько миллионов строк

 Dim str() As String = IO.File.ReadAllLines(pth, System.Text.Encoding.Default)     
        Dim sFind As String = TextBox6.Text
        Dim query = From s As String In str Where InStr(1, s, sFind) = 1 Order By s.Split()(1) Descending
        ListBox1.Items.Clear()
        ListBox1.Items.AddRange((query.ToArray))

     Dim query = From s As String In str Where InStr(1, s, sFind) = 1 Order By DateTime.ParseExact(s.Split()(1) & " " & s.Split()(2), "dd.MM.yyyy HH:mm:ss",
                                       System.Globalization.CultureInfo.InvariantCulture) Descending

        Dim query = From s As String In str _
                  Where InStr(1, s, sFind) = 1 _
                  Order By DateTime.ParseExact(s.Substring(s.IndexOf(" ") + 1), "dd.MM.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture) Descending

 Dim rgx As New Regex("\s(.*)", RegexOptions.IgnoreCase)
'
'
        Dim queryR = From s As String In Lines _
               Where InStr(1, s, sFind) = 1 _
              Order By DateTime.ParseExact(rgx.Match(s).Groups(1).Value, "dd.MM.yyyy HH:mm:ss", System.Globalization.CultureInfo.InvariantCulture) Descending

'...
Dim ss() As String = query.ToArray
Dim myComparer = New cmpDateTime()
Array.Sort(ss, myComparer)
ListBox1.Items.Clear()
ListBox1.Items.AddRange(ss)
'...
 
Public Class cmpDateTime
    Implements IComparer
    Function Compare(ByVal q1 As Object, ByVal q2 As Object) As Integer _
       Implements IComparer.Compare
        Dim s1() As String = DirectCast(q1, String).Split(Chr(32))
        Dim s2() As String = DirectCast(q2, String).Split(Chr(32))
        Dim d1 As Date = Convert.ToDateTime(s1(1) & Chr(32) & s1(2))
        Dim d2 As Date = Convert.ToDateTime(s2(1) & Chr(32) & s2(2))
        Dim t As Integer = Date.Compare(d1, d2)
        Return Date.Compare(d1, d2)
    End Function
End Class

'...
Dim j As Integer
'...
Dim query = From s As String In str Where s.Contains(sFind) Select s
j = query.Count
tm.Stop()
'...