Public Class frmFilter
 
    Dim dttest As New DataTable
    Dim dtselect As New DataTable
 
    Dim dgv As New DataGridView With {.Parent = Me, .Dock = DockStyle.Fill}
 
 
    Private Sub frmFilter_Load(sender As Object, e As EventArgs) Handles _
      MyBase.Load
 
        With dtTest
            .Columns.Add("Id", GetType(Integer))
            .Columns.Add("Vor", GetType(String))
            .Columns.Add("Nach", GetType(String))
 
            .Rows.Add(1, "Test", "Daten")
            .Rows.Add(15, "Robert", "Wer")
            .Rows.Add(18, "Norbert", "Wer")
            .Rows.Add(20, "Silvia", "Was")
            .Rows.Add(21, "Rudi", "Was")
            .Rows.Add(33, "Alles", "Wer")
            .Rows.Add(35, "Tim", "Burst")
            .Rows.Add(37, "Allen", "Cylon")
        End With
 
        dtselect = dttest.Clone
        dtselect.Columns.Add("Häufigkeit", GetType(Integer))
 
        Dim found As Boolean, l As Integer
 
        For i As Integer = 0 To dttest.Rows.Count - 1
            'Suche in übertragenen Sätzen
            found = False
            For k As Integer = 0 To dtselect.Rows.Count - 1
                If dtselect.Rows(k)("Nach").ToString = dttest.Rows(i)( _
                  "Nach").ToString Then
                    found = True : l = k : Exit For
                End If
            Next k
 
 
            If found Then
                'Name bereits vorhanden - Zählen
                dtselect.Rows(l)("Häufigkeit") = CInt(dtselect.Rows(l)( _
                  "Häufigkeit")) + 1
            Else
                'Name nicht vorhanden - Satz hinzufügen
                dtselect.Rows.Add(dttest.Rows(i).ItemArray)
                dtselect.Rows(dtselect.Rows.Count - 1)("Häufigkeit") = 1
            End If
        Next i
 
        dgv.DataSource = dtselect
    End Sub
End Class