[silverlight]

كود :

  Dim stringsArray() As String = RichTextBox1.Lines
       Dim startIndex As Integer = 5
       Dim endIndex As Integer = 20
       For i As Integer = startIndex To endIndex
           Dim txt As String = stringsArray(i)
           ' add lines to richTextBox2
           RichTextBox2.Text += txt + Environment.NewLine
       Next