[RESOLVED] Change a text in richtextbox but keep image in it

I have a richtextbox with images and text.
I want to change specified text but i want to keep my image.
How can i do that.
I use :

Dim aLines() As String = rtbDisplay.Lines
aLines(i) = aLines(i).Replace(str, "")
rtbDisplay.Lines = aLines

but do not work.

You can't using Lines I don't think. You'll have to find the text you want to replace, set SelectionStart and SelectionLength, then set SelectedText.

OK. THANKS JM.
I resolved :

Code:

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Private Sub Hamthaydoidong(ByVal str As String)
        Dim aLines() As String = rtbDisplay.Lines
        If aLines(rtbDisplay.Lines.Length - 2).Contains(str) = True Then
            rtbDisplay.SelectionStart = rtbDisplay.Text.IndexOf(str)
            rtbDisplay.SelectionLength = str.Length
            rtbDisplay.SelectedText = "":duck:
        End If

    End Sub

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