Dim s1 As String = "Some $data hi!"
       Dim s2 As String = "$Data"
       Dim s3 As String
 
       s3 = VB_Replace(s1, s2, "123,456", True)

Imports System.Runtime.CompilerServices
Module MoreStringStuff
    <Extension()> _
    Public Function Replace(ByVal theString As String, ByVal findString As _
    String, ByVal replaceString As String, Optional ByVal comparison As _
    StringComparison = StringComparison.CurrentCulture) As String
        Dim idx As Integer = theString.IndexOf(findString, comparison)
        If idx > -1 Then
            Return theString.Substring(0, idx) & replaceString & _
              theString.Substring(idx + findString.Length)
        End If
        Return theString
    End Function
End Module

        s3 = s1.Replace(s2, "123,456", _
          StringComparison.CurrentCultureIgnoreCase)

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