Example of when the culture parameter of string.Equals (c#) actually makes a difference?

Question

I don’t fully understand the second parameter of string.Equals, and this is because I can’t find any examples of when it would actually make a difference. For example, the example given here is the same, regardless of the value of the second parameter (aside from IgnoreCase): http://msdn.microsoft.com/en-us/library/c64xh8f9.aspx

I am just talking about the values StringComparison.CurrentCulture, InvariantCulture, or Ordinal.
I can understand the difference between these and their IgnoreCase equivalents.

Answer 1

This MSDN page (Best Practices for Using Strings in the .NET Framework) has a lot of information about using strings and the following example is taken from it:

using System;
using System.Globalization;
using System.Threading;

public class Example
{
   public static void Main()
   {
      string[] values= { "able", "ångström", "apple", "Æble", 
                         "Windows", "Visual Studio" };
      Array.Sort(values);
      DisplayArray(values);

      // Change culture to Swedish (Sweden).
      string originalCulture = CultureInfo.CurrentCulture.Name;
      Thread.CurrentThread.CurrentCulture = new CultureInfo("sv-SE");
      Array.Sort(values);
      DisplayArray(values);

      // Restore the original culture.
      Thread.CurrentThread.CurrentCulture = new CultureInfo(originalCulture);
    }

    private static void DisplayArray(string[] values)
    {
      Console.WriteLine("Sorting using the {0} culture:",  
                        CultureInfo.CurrentCulture.Name);
      foreach (string value in values)
         Console.WriteLine("   {0}", value);

      Console.WriteLine();
    }
}
// The example displays the following output:
//       Sorting using the en-US culture:
//          able
//          Æble
//          ångström
//          apple
//          Visual Studio
//          Windows
//       
//       Sorting using the sv-SE culture:
//          able
//          Æble
//          apple
//          Windows
//          Visual Studio
//          ångström

Answer 2

Differences between StringComparison.InvariantCulture and StringComparison.Ordinal are fairly easy to find, since Ordinal means that the string is not normalized before it is compared. So we just have to combine an normalized string to an unnormalized string.

Finding differences between StringComparison.InvariantCulture and StringComparison.CurrentCulture (or differences between different CurrentCultures) is a bit more difficult, but they do exist.

Here is one example:

    string a = "\u00C4";       // "LATIN CAPITAL LETTER A WITH DIAERESIS"
    string b = "\u0041\u0308"; // "LATIN CAPITAL LETTER A" - "COMBINING DIAERESIS"

    Console.WriteLine(a.Equals(b, StringComparison.InvariantCulture)); // true

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US", false);
    Console.WriteLine(a.Equals(b, StringComparison.CurrentCulture));   // true

    Thread.CurrentThread.CurrentCulture = new CultureInfo("da-DK", false);
    Console.WriteLine(a.Equals(b, StringComparison.CurrentCulture));   // false

    Console.WriteLine(a.Equals(b, StringComparison.Ordinal));          // false

Or this one that only uses ASCII characters:

    string ddzs = "ddzs";
    string dzsdzs = "dzsdzs";

    Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US", false);
    Console.WriteLine(ddzs.Equals(dzsdzs, StringComparison.CurrentCulture)); // false

    Thread.CurrentThread.CurrentCulture = new CultureInfo("hu-HU", false);
    Console.WriteLine(ddzs.Equals(dzsdzs, StringComparison.CurrentCulture)); // true