________
Alle Angaben ohne Gewähr. Keine Haftung für Vorschläge, Tipps oder sonstige Hilfe, falls es schiefgeht, nur Zeit verschwendet oder man sonst nicht zufrieden ist

Dim reader As New System.IO.StreamReader("C:\A.txt")
Dim Writer As New System.IO.StreamWriter("C:\A.txt")
Dim txt As String = reader.ReadToEnd
Writer.Write(txt)
Writer.WriteLine("...")
Writer.Close()
reader.Close()

Dim lines() As String = _
System.IO.File.ReadAllLines(Pfad der Datei)
 
Dim fields() As String 
 
for i as integer = 0 to lines.length-1
    fields = lines(i).Split(";"c)

Dim FS As New FileStream("...", FileMode.Append)
Dim SW As New StreamWriter(FS)
 
SW.WriteLine("Neue Zeile")
 
SW.Close()

My.Computer.FileSystem.WriteAllText(pfad, "Neue zeile", True)

________
Alle Angaben ohne Gewähr. Keine Haftung für Vorschläge, Tipps oder sonstige Hilfe, falls es schiefgeht, nur Zeit verschwendet oder man sonst nicht zufrieden ist

"iPod oder EiPott?"

Option Strict On : Option Explicit On : Option Infer Off
Public Class cDataTableCSV
    Inherits System.Data.DataTable
 
    Public Function LoadFile(ByVal filename As String, _
        ByVal textencoder As System.Text.Encoding, _
        Optional ByVal FeldTrennzeichen As Char = ";"c, _
        Optional ByVal ZeilenTrennzeichen As String = _
        Microsoft.VisualBasic.vbNewLine) As Boolean
 
        Me.Rows.Clear() : Me.Columns.Clear()
        Try
            'Zeilen lesen
            Dim lines() As String = _
            System.IO.File.ReadAllLines(filename, textencoder)
            'Maximale Feldzahl pro Zeile
            Dim fields() As String, maxfields As Integer = 0
            For i As Integer = 0 To lines.GetUpperBound(0)
                If lines(i) <> String.Empty Then
                    fields = lines(i).Split(FeldTrennzeichen)
                    maxfields = System.Math.Max(maxfields, fields.Length)
                End If
            Next i
            If maxfields < 1 Then Return False
 
            'Spalten für Felder erstellen
            For i As Integer = 0 To maxfields - 1
                Me.Columns.Add("SP_" + CStr(i), GetType(String))
                'Einige Standardeigenschaften der Spalten
                Me.Columns(i).AllowDBNull = True
                Me.Columns(i).DefaultValue = String.Empty
                Me.Columns(i).ReadOnly = False
            Next i
 
            'Datatable: Zeilen füllen
            Dim r As System.Data.DataRow
            For i As Integer = 0 To lines.GetUpperBound(0)
                If lines(i) <> String.Empty Then
                    fields = lines(i).Split(FeldTrennzeichen)
                    System.Array.Resize(fields, maxfields)
                    r = Me.NewRow
                    For k As Integer = 0 To maxfields - 1
                        If String.IsNullOrEmpty(fields(k)) Then
                            r(k) = String.Empty
                        Else
                            r(k) = fields(k).Trim
                        End If
                    Next k 'Felderschleife
                    Me.Rows.Add(r)
                End If
            Next i
            Return Me.Rows.Count > 0
        Catch ex As System.Exception
            Return False
        End Try
    End Function
 
    Public Function SaveFile _
    (ByVal Filename As String, ByVal Feldtrennzeichen As Char) As Boolean
        If Me.Rows.Count < 1 Then Return False
        Try
            Dim lines(Me.Rows.Count - 1) As String
            Dim fields(Me.Columns.Count - 1) As String
            For i As Integer = 0 To Me.Rows.Count - 1
                'Felder aus der Table zusammenstellen
                For k As Integer = 0 To Me.Columns.Count - 1
                    fields(k) = CType(Me.Rows(i).Item(k), String)
                Next k
                'Felder zusammenfügen
                lines(i) = System.String.Join(Feldtrennzeichen, fields)
                'Leere Spalten am Zeilenende entfernen
                While lines(i).EndsWith(Feldtrennzeichen)
                    lines(i) = lines(i).Substring(0, lines(i).Length - 1)
                End While
            Next i
            'Datei füllen
            System.IO.File.WriteAllLines(Filename, lines)
            Return True
        Catch ex As System.Exception
            Return False
        End Try
    End Function
 
    Public Sub AddColumn()
        Dim k As Integer = Me.Columns.Count
        Dim cn As String = "SP_" & CStr(k)
        Me.Columns.Add(cn, GetType(String))
        For i As Integer = 0 To Me.Rows.Count - 1
            Me.Rows(i).Item(k) = String.Empty
        Next i
    End Sub
End Class