help in richtextbox vb.net

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VB

VS2010

RichTextBox

For j As Integer = 0 To RichTextBox1.Lines.Length - 1

           Dim lines() As String = Me.RichTextBox1.Lines
           RichTextBox1.SelectedText = lines(j).IndexOf("http")
           RichTextBox1.SelectionLength = (30)

           RichTextBox2.Text = RichTextBox1.SelectedText.ToString



       Next

i want to copy all lines in richtextbox1 contain word "http", i follow this code but it showing different error.
can anyone suggest other code or help in this code :)