'richtextbox1 Quelle
 
 Dim text As String = "hi hi hi hi hi" 'Der inhalt in dem "gesucht" werden soll.
 
'er soll hier aber den Inhalt der richtextbox1 benutzen 
 
 
 
 Dim searchTerm As String = "hi"  ' der inhalt der "durchsucht" werden soll.
 
'er soll hier auch den Inhalt der richtextbox1 benutzen 
 
 
 
 
       Dim dataSource As String() = text.Split(New Char() {" ", ",", ".", ";", _
         ":"},
                                                 StringSplitOptions.RemoveEmpty_
                                                 Entries)
 
 
        Dim matchQuery = From word In dataSource
                      Where word.ToLowerInvariant() = _
                        searchTerm.ToLowerInvariant()
                      Select word
 
 
        Dim count As Integer = matchQuery.Count()
 
        RichTextBox2.Text = searchTerm & count 
 
 
' Ergebniss  >>>>> hi 6

Dim Richtextbox1 As New RichTextBox
Richtextbox1.LoadFile("Pfad/Name der RTF Datei")
 
Dim searchTerm As String = "Regelung"
Dim anz As Integer = CountWord(richtextbox1.Text, searchTerm)
 
Dim wordindex As Integer = -1, counter As Integer = 0
 
Do
 
   wordindex = Richtextbox1.Find_
    (searchTerm, wordindex + 1, RichTextBoxFinds.WholeWord)
 
   If Not wordindex = -1 Then
      Richtextbox1.SelectionStart = wordindex
      counter += 1
   End If
 
Loop While Not wordindex = -1

Public Function CountWord(ByVal text As String, _
            ByVal wordtocount As String) As Integer
 
    If String.IsNullOrWhiteSpace(text) Then Return -1
    If String.IsNullOrWhiteSpace(wordtocount) Then Return -1
 
    wordtocount = GetWord(wordtocount)
 
    Dim splitchars As String = " ,;.:?!"
 
    Dim dataSource As String() = _
     text.Split(splitchars.ToArray, _
     StringSplitOptions.RemoveEmptyEntries)
 
    Dim matchquery As IEnumerable(Of String) = _
     From word As String In dataSource _
     Where String.Compare(GetWord(word), wordtocount, True) = 0
 
    Return matchquery.Count()
 
End Function
 
 
 
Private Function GetWord(ByVal word As String) As String
 
    If String.IsNullOrWhiteSpace(word) Then Return String.Empty
 
    Dim trimchars As String = "<>[]{}()+-*/\|@#"
 
    word = word.Trim(trimchars.ToArray)
 
    Return word
 
End Function

Dim anz As Integer = CountWord(Richtextbox1.Text, searchTerm)

'Datei öffnen , laden
        Using OpenFileDialog1 As New OpenFileDialog
            OpenFileDialog1.InitialDirectory = Application.StartupPath
            If OpenFileDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
 
                Dim lines() As String = System.IO.File.ReadAllLines( _
                  OpenFileDialog1.FileName, System.Text.Encoding.Default) _
                  'Umlaute Aktivieren[System.Text.Encoding.Default] 2/3
 
                'Reader.Items.Clear()
                For Each line As String In lines
                    Dim Split() As String = line.Split()
                    Dim saubermachen As New ListViewItem(New String() {Split( _
                      0), Split(1), Split(2)})   'Umlaute 
                    ' Aktivieren[System.Text.Encoding.Default] 2/3
 
                    'Datei Lesen
                    c.AppendText(line) 'einfügen
                Next
                'Jetzt erst Säubern, [ist schneller]
 
 
                Dim line1 As String = "-,_|~:#12345678910."
                c.Text = Regex.Replace(c.Text, line1 & "\t]+|[" & line1 & _
                  "\t]+", String.Empty, RegexOptions.Multiline)   'zahlen 
                ' Entfernen
                ToolStripStatusLabel2.Text = "Geöffnete Liste: " & _
                  OpenFileDialog1.SafeFileName
 
                'wir haben eine Saubere richtextbox1 mit Wörtern drin, jetzt 
                ' verwenden wir sie als Such Quelle. 
 
'soon
 
 
            End If
        End Using
    End Sub

'Datei öffnen , laden
        Using OpenFileDialog1 As New OpenFileDialog
            OpenFileDialog1.InitialDirectory = Application.StartupPath
            If OpenFileDialog1.ShowDialog() = Windows.Forms.DialogResult.OK Then
                Dim lines() As String = System.IO.File.ReadAllLines( _
                  OpenFileDialog1.FileName, System.Text.Encoding.Default)
                Dim myReader As StreamReader
                myReader = New StreamReader(OpenFileDialog1.FileName, _
                  System.Text.ASCIIEncoding.Default)
                c.AppendText(myReader.ReadToEnd)
                RegexOptions.Multiline)  
                End If
        End Using