Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
        MySource.AddRange(New String() _
      { _
          "@outlook.com", _
          "@hotmail.com", _
          "@stofanet.dk", _
          "@gmail.com", _
          "@nuhme.dk"
      })
        With TextBox1
            .AutoCompleteCustomSource = MySource
            .AutoCompleteMode = AutoCompleteMode.SuggestAppend
            .AutoCompleteSource = AutoCompleteSource.CustomSource
        End With
    End Sub
 
   Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles _
     TextBox1.TextChanged
        If TextBox1.Text.Length > 0 Then
            t = TextBox1.Text(TextBox1.Text.Length - 1)
            If t = "@" Then
 
            End If
        End If
    End Sub