在Richtext框VB.net中替换文本

Question

我正在解决富文本框（V​​B.net）中的文本中的一个问题。这是行不通的。

你知道我有问题吗？

Dim number_lines As Integer
number_lines = RichTextBox1.Lines.Count
Dim counting As Integer
counting = 0
For Each line As String In RichTextBox1.Lines
    counting = counting + 1

    If ((number_lines - 1) = counting) Or (number_lines = counting) Then

    Else
        If line.Contains("M30") Then
           Me.RichTextBox1.Lines(counting).Replace("M30", "")
        End If

        If line.Contains("M406") Then
            Me.RichTextBox1.Lines(counting).Replace("M406", "M405")
            'line.Replace("M406", "M405")
        End If
    End If
Next line