.NET (Core and Framework)

'To load the favourites on startup:    
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        For Each item As String In "C:/Program Files/Testfile.txt"
            ComboBox1.Items.Add(item)
        Next
    End Sub

    'To add the content of a textbox to your favourites   
    Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
        texty.Text = WebBrowser1.Url.ToString()



        'If My.Settings.Favourites.Contains(texty.Text) Then
        ' MessageBox.Show("It has been in your favourites!")
        'Else
        '


        ComboBox1.Items.Add(texty.Text)

        Dim objStreamWriter As StreamWriter

        'Pass the file path and the file name to the StreamWriter constructor.
        objStreamWriter = New StreamWriter("C:\Program Files\Testfile.txt")

        'Write a line of text.
        objStreamWriter.WriteLine(texty.Text)

        

        'Close the file.
        objStreamWriter.Close()


        'End If
    End Sub




    Private Sub ToolStripButton2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ToolStripButton2.Click
        WebBrowser1.Navigate(ComboBox1.Text)

    End Sub