Public i As Integer
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim counter As Integer
        Dim tempArray() As String
        tempArray = richtextBox1.Lines
        counter = tempArray.GetUpperBound(0)
        For i = 0 To counter
            RichTextBox2.Text = RichTextBox2.Text + tempArray(i) + vbCrLf
            If (i >= counter) Then MsgBox("已到内容尾端 ")

        Next i

    End Sub