Imports System
Imports System.Text
Public Class Test
Public Shared Function string_char_tolower(s As String, idx as Integer) As String
Dim len As Integer = s.Length
If (idx > len Or idx < 0) Then
return s
End If
Dim sb As StringBuilder = new StringBuilder(s)
sb(idx) = Char.ToLower(sb(idx))
return sb.ToString()
End Function
Public Shared Sub Main()
Dim s As String = "VB.NET PROGRAMMING"
s = string_char_tolower(s, 4)
Console.Write(s)
End Sub
End Class
' run:
'
' VB.NeT PROGRAMMING