Suche in RichTextBox vb.net

Dim index As Integer = 0

'TextBox1 = text to be searched in the rich text box
'RichTextBox1 = text being searched

While index < RichTextBox1.Text.LastIndexOf(TextBox1.Text)
	RichTextBox1.Find(TextBox1.Text, index, RichTextBox1.TextLength, RichTextBoxFinds.None)
	RichTextBox1.SelectionBackColor = Color.Turquoise
	index = RichTextBox1.Text.IndexOf(TextBox1.Text, index) + 1
End While
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