OK i have this code that changes the color of word in a rtb can someone help convert it to .net?

Code:
Public Sub HighlightText(sKeyword As String)

Dim nStart As Integer, sPrevChar As String, sNextChar As String
    
nStart = InStr(1, LCase(frmIM.rtbRecever.Text), sKeyword)

Do While nStart <> 0
If nStart > 1 Then
    sPrevChar = Mid$(frmIM.rtbRecever.Text, nStart - 1, 1)
Else
    sPrevChar = " "
End If
                                                

If Len(frmIM.rtbRecever.Text) >= nStart + Len(sKeyword) Then
    sNextChar = Mid$(frmIM.rtbRecever.Text, nStart + Len(sKeyword), 1)
Else
    sNextChar = " "
End If
                                         

If (sPrevChar = Chr(32) Or sPrevChar = Chr(13) Or _
sPrevChar = Chr(10) Or sPrevChar = Chr(9)) And _
(sNextChar = Chr(32) Or sNextChar = Chr(13) Or _
sNextChar = Chr(10) Or sNextChar = Chr(9)) Then

With frmIM.rtbRecever

    .SelStart = nStart - 1
    .SelLength = Len(sKeyword)
    .SelColor = vbBlue
    .SelText = UCase(sKeyword)
    .SelStart = Len(frmIM.rtbRecever.Text)
    .SelColor = vbBlack

End With
End If

                                                

nStart = InStr(nStart + Len(sKeyword), LCase(frmIM.rtbRecever.Text), sKeyword)

Loop

End Sub
Code:
Private Sub rtbRecever_Change()

With rtbRecever
    .SelStart = 0
    .SelLength = Len(.Text)
    .SelColor = vbBlack
    .SelStart = Len(.Text)
End With

                                            
' You can add words to the highlight list. I have game you
' a few to start off with.
HighlightText frmIMSettings.txtScreenName.Text
HighlightText "brb"
HighlightText "lol"
HighlightText "G2G"
HighlightText "visual basic"
HighlightText "java"
                            
End Sub