Imports System
Imports System.Globalization
Imports System.Threading

Class Sample
  Shared Sub Main()
    Console.WriteLine(Thread.CurrentThread.CurrentCulture)

    Console.WriteLine("Compare CurrentCulture             : {0}", String.Compare("i", "I", StringComparison.CurrentCulture))
    Console.WriteLine("Compare CurrentCultureIgnoreCase   : {0}", String.Compare("i", "I", StringComparison.CurrentCultureIgnoreCase))
    Console.WriteLine("Compare InvariantCulture           : {0}", String.Compare("i", "I", StringComparison.InvariantCulture))
    Console.WriteLine("Compare InvariantCultureIgnoreCase : {0}", String.Compare("i", "I", StringComparison.InvariantCultureIgnoreCase))

    Console.WriteLine("{0} => {1}", "i", "i".ToUpper())
    Console.WriteLine("{0} => {1}", "I", "I".ToLower())

    ' 現在のスレッドのカルチャをtr-TR(トルコ語/トルコ)に変更
    Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("tr-TR")

    Console.WriteLine(Thread.CurrentThread.CurrentCulture)

    Console.WriteLine("Compare CurrentCulture             : {0}", String.Compare("i", "I", StringComparison.CurrentCulture))
    Console.WriteLine("Compare CurrentCultureIgnoreCase   : {0}", String.Compare("i", "I", StringComparison.CurrentCultureIgnoreCase))
    Console.WriteLine("Compare InvariantCulture           : {0}", String.Compare("i", "I", StringComparison.InvariantCulture))
    Console.WriteLine("Compare InvariantCultureIgnoreCase : {0}", String.Compare("i", "I", StringComparison.InvariantCultureIgnoreCase))

    Console.WriteLine("{0} => {1}", "i", "i".ToUpper())
    Console.WriteLine("{0} => {1}", "I", "I".ToLower())
  End Sub
End Class

ja-JP
Compare CurrentCulture             : -1
Compare CurrentCultureIgnoreCase   : 0
Compare InvariantCulture           : -1
Compare InvariantCultureIgnoreCase : 0
i => I
I => i
tr-TR
Compare CurrentCulture             : 1
Compare CurrentCultureIgnoreCase   : 1
Compare InvariantCulture           : -1
Compare InvariantCultureIgnoreCase : 0
i => İ
I => ı