Текстовый редактор: копирование, вставка и удаление текста - Visual Basic .NET

Public Class Form1
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        TextBox1.multiline = True
        TextBox1.Clear()
        Me.Text = "Простой текстовый редактор"
        OpenFileDialog1.FileName = Nothing
        OpenFileDialog1.Filter = "Текстовые файлы (*.txt) |'.txt|A11 files (*.*)|*.*"
        SaveFileDialog1.Filter = "Текстовые файлы (f.txt) |*.txt|A11 files (*.*)|*.*"
    End Sub
    Private Sub ФайлToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ФайлToolStripMenuItem.Click
        OpenFileDialog1.ShowDialog()
        If OpenFileDialog1.FileName = Nothing Then Exit Sub
        Try
            Dim Читатель As New IO.StreamReader(OpenFileDialog1.FileName, System.Text.Encoding.GetEncoding(1251))
            Читатель.Close()
        Catch Exc As System.IO.FileNotFoundException
            MessageBox.Show("Нет такого файла", "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
        Catch Exc As Exception
            MessageBox.Show(Exc.Message, "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
 
        End Try
    End Sub
    Private Sub СохранитьКакToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles СохранитьКакToolStripMenuItem.Click
        SaveFileDialog1.FileName = SaveFileDialog1.FileName
        If SaveFileDialog1.ShowDialog = DialogResult.OK Then Запись()
    End Sub
    Sub Запись()
        Try
            Dim Писатель As New IO.StreamWriter(SaveFileDialog1.FileName, False, System.Text.Encoding.GetEncoding(1251))
            Писатель.Write(TextBox1.Text)
            Писатель.Close()
            TextBox1.Modified = False
        Catch Exc As Exception
            MessageBox.Show(Exc.Message, "Ошибка", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
        End Try
    End Sub
    Private Sub ВыходToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ВыходToolStripMenuItem.Click
        Me.Close()
    End Sub
    Private Sub Form1_Closeing(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
        If TextBox1.Modified - False Then Exit Sub
        Dim MBox As DialogResult
        MessageBox.Show("Текст был изменен." & vbCrLf & "Сохранить изменения?", "Простой редактор", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Exclamation)
        If MBox = DialogResult.No Then Exit Sub
        If MBox = DialogResult.Cancel Then e.Cancel = True
        If MBox = DialogResult.Yes Then
            If SaveFileDialog1.ShowDialog = DialogResult.OK Then
                Запись() : Exit Sub
            Else
                e.Cancel = True
            End If
        End If
    End Sub
   
    Private Sub ВставитьToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ВставитьToolStripMenuItem.Click
        Clipboard.Clear() 
        Clipboard.SetText(RichTextBox1.SelectedText) 
        RichTextBox1.SelectedText = Clipboard.GetText() 
    End Sub
 
    Private Sub ШрифтToolStripMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ШрифтToolStripMenuItem.Click
        FontDialog1.ShowColor = True
        FontDialog1.ShowDialog()
        RichTextBox1.SelectionFont = FontDialog1.Font
        RichTextBox1.SelectionColor = FontDialog1.Color
    End Sub
 
    Private Function FontDialog1() As Object
        Throw New NotImplementedException
    End Function