How to Append Text character by character?

Dim Counter as integer = 0
Dim String1 as string = "This is typed character-by-character!"

If Not Counter > String1.Length - 1 Then
  TextBox1.AppendText(String1(Counter))
  Counter += 1
Else
  Timer1.Enabled = False
  Counter = 0
End If

Imports System.Threading
Public Class Form1
    Delegate Sub AppTextCallback(ByVal [text] As String)
    Dim Thread1 As Thread
    Dim Counter As Short
    Dim String1 As String = "This string is typed character by character. It is just fine in the beginning of the text, but as the string becomes longer and longer, then, the blinking issues appear to the viewer! This string is typed character by character. It is just fine in the beginning of the text, but as the string becomes longer and longer, then, the blinking issues appear to the viewer!"

    Private Sub AppTxtThread()
        While (Counter < String1.Length)
            AppText(String1(Counter))
            Thread.Sleep(100)
            Counter += 1
        End While
    End Sub


    Private Sub AppText(ByVal [text] As String)
        If TextBox1.InvokeRequired Then
            Dim d As New AppTextCallback(AddressOf AppText)
            Me.Invoke(d, New Object() {[text]})
        Else
            TextBox1.Select()
            TextBox1.AppendText([text])
            TextBox1.SelectionStart = TextBox1.Text.Length
        End If
    End Sub


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        'ThreadSafe Method
        Thread1 = New Thread(AddressOf AppTxtThread)
        Thread1.IsBackground = True
        Thread1.Start()
    End Sub


    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        'Regular Method
        Counter = 0
        TextBox1.Select()
        While (Counter < String1.Length)
            TextBox1.AppendText(String1(Counter))
            TextBox1.SelectionStart = TextBox1.Text.Length
            Thread.Sleep(100)
            Counter += 1
        End While
    End Sub
End Class

Imports System.Threading
Public Class Form1
    Public Delegate Sub AppendDelegate(ByVal aString As Char)
    Public Delegate Sub CheckSetDelegate(ByVal Status As Boolean)
    Dim Thread1 As Thread
    Dim C As Short
    Dim String1 As String = "This string is typed using threads. How is the performance?"
    Dim WaitHandle As ManualResetEvent
    
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Thread1 = New Thread(AddressOf AppTxtThread)
        'Thread1.IsBackground = True
        WaitHandle = New ManualResetEvent(False)
    End Sub


    Private Sub AppTxtThread()
        While (C < String1.Length)
            WaitHandle.WaitOne()
            TextBox1.Invoke(New AppendDelegate(AddressOf AppendTxt), String1(C))
            C += 1
            Thread.Sleep(100)
        End While
        CheckBox1.Invoke(New CheckSetDelegate(AddressOf CheckboxSet), False)
        C = 0
    End Sub


    Private Sub AppendTxt(ByVal Chr As Char)
        TextBox1.AppendText(Chr)
    End Sub


    Private Sub CheckboxSet(ByVal Stat As Boolean)
        If Stat = False Then
            CheckBox1.Checked = False
        Else
            CheckBox1.Checked = True
        End If
    End Sub


    Private Sub CheckToggled(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CheckBox1.CheckedChanged
        If CheckBox1.Checked Then
            If Thread1.ThreadState = ThreadState.Unstarted Then
                Thread1.Start()
            ElseIf Thread1.ThreadState = ThreadState.Stopped Then
                Thread1 = New Thread(AddressOf AppTxtThread)
                Thread1.Start()
            End If
            WaitHandle.Set()
        Else
            WaitHandle.Reset()
        End If
    End Sub
End Class