Открытие, поиск и замена текста, сохранение измененного файла

Imports System.IO
 
Public Class Form1
    Dim path As String
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        OpenFileDialog1.ShowDialog()
        path = OpenFileDialog1.FileName
        Label1.Text = OpenFileDialog1.FileName
        If OpenFileDialog1.FileName > " " Then
            Dim strreader As New StreamReader(OpenFileDialog1.FileName, System.Text.Encoding.UTF8)
            Dim text As String = strreader.ReadToEnd
            TextBox1.Text = text
            strreader.Close()
        Else
            MessageBox.Show("Необходимо выбрать файл")
        End If
 
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        SaveFileDialog1.ShowDialog()
        path = SaveFileDialog1.FileName
        If SaveFileDialog1.FileName > " " Then
            Label2.Text = path
            WriteFile()
        End If
 
    End Sub
 
    Sub WriteFile()
        Dim strwr As New StreamWriter(path)
        strwr.Write(TextBox1.Text, System.Text.Encoding.GetEncoding(1251))
        strwr.Close()
    End Sub
 
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        WriteFile()
    End Sub
End Class

        Dim Txt As String = IO.File.ReadAllText("C:\1.txt", System.Text.Encoding.Default)
        Txt = Txt.Replace("Old", "new")
        IO.File.WriteAllText("C:\2.txt", Txt, System.Text.Encoding.Default)

Option Compare Text

        Dim input As String = "        09261114282D"
        Dim output As String = input
 
        Dim pattern As String = "^        [0-9]{11}D"
 
        Dim regexp As Regex = New Regex(pattern)
 
        If regexp.IsMatch(input) Then
            output = input.Replace("        ", "-ISIS-")
        End If
 
        MsgBox(output)

Imports System.Text.RegularExpressions

Txt = Txt.Replace("          ###########D", "  -ISIS-  ###########D")

        Dim pattern As String = "^        [0-9]{11}D"
 
        Dim regexp As Regex = New Regex(pattern)
 
        Dim Txt() As String = IO.File.ReadAllLines("C:\1.txt", System.Text.Encoding.Default)
 
        For x = 0 To Txt.Length - 1
            If regexp.IsMatch(Txt(x)) Then
                Txt(x) = Txt(x).Replace("        ", "-ISIS-")
            End If
        Next
 
 
        IO.File.WriteAllLines("C:\2.txt", Txt, System.Text.Encoding.Default)

Imports System.Text.RegularExpressions
 
Public Class Form1
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim text(2000000) As String
        For x = 0 To 2000000
 
            If x Mod 10000 = 0 Then
                text(x) = "        " & Rnd() * 55555555 \ 1 + 10000000000 & "D"
            Else
                text(x) = Rnd() * 5000000 & "rrrr fffff aaa" & x
            End If
        Next
 
        IO.File.WriteAllLines("C:\3.txt", text, System.Text.Encoding.Default)
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim pattern As String = "^        [0-9]{11}D"
 
        Dim regexp As Regex = New Regex(pattern)
 
        Dim Txt() As String = IO.File.ReadAllLines("C:\3.txt", System.Text.Encoding.Default)
        Dim y As Integer
        For x = 0 To Txt.Length - 1
            If regexp.IsMatch(Txt(x)) Then
                Txt(x) = Txt(x).Replace("        ", "-ISIS-")
                y += 1
            End If
        Next
 
 
        IO.File.WriteAllLines("C:\4.txt", Txt, System.Text.Encoding.Default)
        MsgBox(y)
    End Sub
End Class

     Dim pattern As String = "[*]E[*]"
                Dim regexp As Regex = New Regex(pattern)
                Dim Txt() As String = IO.File.ReadAllLines(OpenFileDialog1.FileName, System.Text.Encoding.Default)
                For x = 0 To Txt.Length - 1
                    If regexp.IsMatch(Txt(x)) Then
                        Txt(x) = Txt(x).Replace("[*]E[*]", "[кавычка]")
                    Exit For                    
                    End If
                    
                Next
 
                Dim pattern As String = "\n"
                Dim regexp As Regex = New Regex(pattern)
                Dim Txt() As String = IO.File.ReadAllLines(OpenFileDialog1.FileName, System.Text.Encoding.Default)
                For x = 0 To Txt.Length - 1
                    If regexp.IsMatch(Txt(x)) Then
                        Txt(x) = Txt(x).Replace("\n", ", ")
                    End If
                    Next
 
                IO.File.WriteAllLines("C:\2.txt", Txt, System.Text.Encoding.Default)

Replace("олд", "нью")

S = S.Relace(VbCrLf, ", ")

Dim pattern As String = "VbCrLf"
                Dim regexp As Regex = New Regex(pattern)
                Dim Txt() As String = IO.File.ReadAllLines(OpenFileDialog1.FileName, System.Text.Encoding.Default)
                For x = 0 To Txt.Length - 1
                    If regexp.IsMatch(Txt(x)) Then
                        Txt(x) = Txt(x).Replace("VbCrLf", ", ")
                        strc = strc + 1
                    End If
                Next