feat: Update example of String Format instead of just round trip

src/Chapter02.Tests/Listing02.09.Tests.cs

@@ -1,4 +1,4 @@
-using AddisonWesley.Michaelis.EssentialCSharp.Shared;
+using System.Globalization;
 
 namespace AddisonWesley.Michaelis.EssentialCSharp.Chapter02.Listing02_09.Tests;
 
@@ -8,19 +8,14 @@ public class ProgramTests
     [TestMethod]
     public void Main_WriteBooleanStatements()
     {
-        string netCoreApp2expected =
-$@"False: {1.61803398874989} == {1.61803398874989}
-True: {1.61803398874989} == {1.61803398874989}";
-
-        string expected = // netcoreapp3.0 and later
-$@"True: {1.618033988749895} == {1.618033988749895}
-True: {1.618033988749895} == {1.618033988749895}";
-
-        string netCoreVersion = NetCore.GetNetCoreVersion();
-        if (string.Compare(netCoreVersion, "3")<0)
-        {
-            expected = netCoreApp2expected;
-        }
+        var number = 86540910.21;
+        string currentCultureString = number.ToString("C");
+        string greekCultureString = number.ToString("C", CultureInfo.GetCultureInfo("el-GR"));
+        string expected =
+$@"{number}
+{currentCultureString}
+True: {currentCultureString} == {currentCultureString}
+{greekCultureString}";
 
         IntelliTect.TestTools.Console.ConsoleAssert.Expect(
                 expected, Program.Main);

src/Chapter02/Listing02.09.UsingStringFormat.cs

@@ -0,0 +1,32 @@
+namespace AddisonWesley.Michaelis.EssentialCSharp.Chapter02.Listing02_09;
+
+using System;
+using System.Globalization;
+
+public class Program
+{
+    public static void Main()
+    {
+        #region INCLUDE
+        // ...
+        const double number = 86540910.21;
+        string currencyText;
+
+        currencyText = $"{number}";
+        Console.WriteLine(currencyText);
+
+        currencyText = $"{number:C}";
+        Console.WriteLine(currencyText);
+
+        // Prove that string interpolation and the ToString method produce equivalent results with format specifiers
+        string toStringCurrencyText = number.ToString("C");
+        Console.WriteLine($"{currencyText == toStringCurrencyText}: {currencyText} == {toStringCurrencyText}");
+
+        // el-GR represents the Greek locale code
+        toStringCurrencyText = number.ToString("C", CultureInfo.GetCultureInfo("el-GR"));
+        Console.WriteLine(toStringCurrencyText);
+
+        // ...
+        #endregion INCLUDE
+    }
+}