Initial commit

vs4win/Chapter05/Chapter05.sln

@@ -3,9 +3,11 @@ Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio Version 17
 VisualStudioVersion = 17.2.32210.308
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "PacktLibrary", "PacktLibrary\PacktLibrary.csproj", "{9E796C3B-6FF6-4E0A-8B6D-A591B6FD1308}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PacktLibrary", "PacktLibrary\PacktLibrary.csproj", "{9E796C3B-6FF6-4E0A-8B6D-A591B6FD1308}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "PeopleApp", "PeopleApp\PeopleApp.csproj", "{DF7885A2-C9F1-4959-9D13-C72E5E77CCDA}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PeopleApp", "PeopleApp\PeopleApp.csproj", "{DF7885A2-C9F1-4959-9D13-C72E5E77CCDA}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Namespaces", "Namespaces\Namespaces.csproj", "{AA8F156C-1105-4AB2-8C42-637990E44EB4}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -21,6 +23,10 @@ Global
 		{DF7885A2-C9F1-4959-9D13-C72E5E77CCDA}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{DF7885A2-C9F1-4959-9D13-C72E5E77CCDA}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{DF7885A2-C9F1-4959-9D13-C72E5E77CCDA}.Release|Any CPU.Build.0 = Release|Any CPU
+		{AA8F156C-1105-4AB2-8C42-637990E44EB4}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{AA8F156C-1105-4AB2-8C42-637990E44EB4}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{AA8F156C-1105-4AB2-8C42-637990E44EB4}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{AA8F156C-1105-4AB2-8C42-637990E44EB4}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

vs4win/Chapter05/Namespaces/France.Paris.cs

@@ -0,0 +1,6 @@
+namespace France
+{
+  public class Paris
+  {
+  }
+}

vs4win/Chapter05/Namespaces/Namespaces.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vs4win/Chapter05/Namespaces/Program.cs

@@ -0,0 +1,10 @@
+using France;
+using us = Texas; // us becomes alias for the namespace and it is not imported
+using Env = System.Environment;
+
+Paris p1 = new();
+us.Paris p2 = new();
+
+WriteLine(Env.OSVersion);
+WriteLine(Env.MachineName);
+WriteLine(Env.CurrentDirectory);

vs4win/Chapter05/Namespaces/Texas.Paris.cs

@@ -0,0 +1,6 @@
+namespace Texas
+{
+  public class Paris
+  {
+  }
+}

vs4win/Chapter06/Ch06Ex02Inheritance/Ch06Ex02Inheritance.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vs4win/Chapter06/Ch06Ex02Inheritance/Circle.cs

@@ -0,0 +1,29 @@
+namespace Packt.Shared;
+
+public class Circle : Square
+{
+  public Circle() { }
+
+  public Circle(double radius) : base(width: radius * 2) { }
+
+  public double Radius
+  {
+    get
+    {
+      return height / 2;
+    }
+    set
+    {
+      Height = value * 2;
+    }
+  }
+
+  public override double Area
+  {
+    get
+    {
+      double radius = height / 2;
+      return Math.PI * radius * radius;
+    }
+  }
+}

vs4win/Chapter06/Ch06Ex02Inheritance/Program.cs

@@ -0,0 +1,10 @@
+using Packt.Shared;
+
+Rectangle r = new(height: 3, width: 4.5);
+WriteLine($"Rectangle H: {r.Height}, W: {r.Width}, Area: {r.Area}");
+
+Square s = new(5);
+WriteLine($"Square    H: {s.Height}, W: {s.Width}, Area: {s.Area}");
+
+Circle c = new(radius: 2.5);
+WriteLine($"Circle    H: {c.Height}, W: {c.Width}, Area: {c.Area}");

vs4win/Chapter06/Ch06Ex02Inheritance/Rectangle.cs

@@ -0,0 +1,20 @@
+namespace Packt.Shared;
+
+public class Rectangle : Shape
+{
+  public Rectangle() { }
+
+  public Rectangle(double height, double width)
+  {
+    this.height = height;
+    this.width = width;
+  }
+
+  public override double Area
+  {
+    get
+    {
+      return height * width;
+    }
+  }
+}

vs4win/Chapter06/Ch06Ex02Inheritance/Shape.cs

@@ -0,0 +1,37 @@
+namespace Packt.Shared;
+
+public abstract class Shape
+{
+  // fields
+  protected double height;
+  protected double width;
+
+  // properties
+  public virtual double Height
+  {
+    get
+    {
+      return height;
+    }
+    set
+    {
+      height = value;
+    }
+  }
+
+  public virtual double Width
+  {
+    get
+    {
+      return width;
+    }
+    set
+    {
+      width = value;
+    }
+  }
+
+  // Area must be implemented by derived classes
+  // as a read-only property
+  public abstract double Area { get; }
+}

vs4win/Chapter06/Ch06Ex02Inheritance/Square.cs

@@ -0,0 +1,26 @@
+namespace Packt.Shared;
+
+public class Square : Rectangle
+{
+  public Square() { }
+
+  public Square(double width) : base(height: width, width: width) { }
+
+  public override double Height
+  {
+    set
+    {
+      height = value;
+      width = value;
+    }
+  }
+
+  public override double Width
+  {
+    set
+    {
+      height = value;
+      width = value;
+    }
+  }
+}

vs4win/Chapter06/Chapter06.sln

@@ -0,0 +1,49 @@
+
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.2.32210.308
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PacktLibrary", "PacktLibrary\PacktLibrary.csproj", "{6D52FBD2-D3F0-478F-9820-5C5786D4EAC0}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "PeopleApp", "PeopleApp\PeopleApp.csproj", "{AE82F198-19F8-4AE9-B1C4-2B04D5EE3EEF}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "NullHandling", "NullHandling\NullHandling.csproj", "{879C7E63-B7FE-4FE4-B3D4-C7CB24C3A73E}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "CodeAnalyzing", "CodeAnalyzing\CodeAnalyzing.csproj", "{2E477494-6458-437D-8CB7-A1803A64786C}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Ch06Ex02Inheritance", "Ch06Ex02Inheritance\Ch06Ex02Inheritance.csproj", "{BE4C568B-3904-42DA-8F46-14E0F76E7BED}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{6D52FBD2-D3F0-478F-9820-5C5786D4EAC0}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{6D52FBD2-D3F0-478F-9820-5C5786D4EAC0}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{6D52FBD2-D3F0-478F-9820-5C5786D4EAC0}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{6D52FBD2-D3F0-478F-9820-5C5786D4EAC0}.Release|Any CPU.Build.0 = Release|Any CPU
+		{AE82F198-19F8-4AE9-B1C4-2B04D5EE3EEF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{AE82F198-19F8-4AE9-B1C4-2B04D5EE3EEF}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{AE82F198-19F8-4AE9-B1C4-2B04D5EE3EEF}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{AE82F198-19F8-4AE9-B1C4-2B04D5EE3EEF}.Release|Any CPU.Build.0 = Release|Any CPU
+		{879C7E63-B7FE-4FE4-B3D4-C7CB24C3A73E}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{879C7E63-B7FE-4FE4-B3D4-C7CB24C3A73E}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{879C7E63-B7FE-4FE4-B3D4-C7CB24C3A73E}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{879C7E63-B7FE-4FE4-B3D4-C7CB24C3A73E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{2E477494-6458-437D-8CB7-A1803A64786C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{2E477494-6458-437D-8CB7-A1803A64786C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{2E477494-6458-437D-8CB7-A1803A64786C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{2E477494-6458-437D-8CB7-A1803A64786C}.Release|Any CPU.Build.0 = Release|Any CPU
+		{BE4C568B-3904-42DA-8F46-14E0F76E7BED}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{BE4C568B-3904-42DA-8F46-14E0F76E7BED}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{BE4C568B-3904-42DA-8F46-14E0F76E7BED}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{BE4C568B-3904-42DA-8F46-14E0F76E7BED}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(SolutionProperties) = preSolution
+		HideSolutionNode = FALSE
+	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {188D9438-CE6A-4BA3-92E6-3220E788EBD1}
+	EndGlobalSection
+EndGlobal

vs4win/Chapter06/CodeAnalyzing/CodeAnalyzing.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+		<GenerateDocumentationFile>true</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.406">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+	<ItemGroup>
+		<None Remove="stylecop.json" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<AdditionalFiles Include="stylecop.json" />
+	</ItemGroup>
+
+</Project>

vs4win/Chapter06/CodeAnalyzing/Program.cs

@@ -0,0 +1,23 @@
+// <copyright file="Program.cs" company="Packt">
+// Copyright (c) Packt. All rights reserved.
+// </copyright>
+namespace CodeAnalyzing;
+
+using System.Diagnostics;
+
+/// <summary>
+/// The main class for this console app.
+/// </summary>
+public class Program
+{
+  /// <summary>
+  /// The main entry point for this console app.
+  /// </summary>
+  /// <param name="args">
+  /// A string array of arguments passed to the console app.
+  /// </param>
+  public static void Main(string[] args)
+  {
+    Debug.WriteLine("Hello, Debugger!");
+  }
+}

vs4win/Chapter06/CodeAnalyzing/stylecop.json

@@ -0,0 +1,12 @@
+{
+  "$schema": "https://raw.githubusercontent.com/DotNetAnalyzers/StyleCopAnalyzers/master/StyleCop.Analyzers/StyleCop.Analyzers/Settings/stylecop.schema.json",
+  "settings": {
+    "orderingRules": {
+      "usingDirectivesPlacement": "preserve"
+    },
+    "documentationRules": {
+      "companyName": "Packt",
+      "copyrightText": "Copyright (c) Packt. All rights reserved."
+    }
+  }
+}

vs4win/Chapter06/NullHandling/Address.cs

@@ -0,0 +1,7 @@
+public class Address
+{
+  public string? Building;
+  public string Street = string.Empty;
+  public string City = string.Empty;
+  public string Region = string.Empty;
+}

vs4win/Chapter06/NullHandling/NullHandling.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vs4win/Chapter06/NullHandling/Program.cs

@@ -0,0 +1,29 @@
+int thisCannotBeNull = 4;
+//thisCannotBeNull = null; // compile error!
+WriteLine(thisCannotBeNull);
+
+int? thisCouldBeNull = null;
+
+WriteLine(thisCouldBeNull);
+WriteLine(thisCouldBeNull.GetValueOrDefault());
+
+thisCouldBeNull = 7;
+
+WriteLine(thisCouldBeNull);
+WriteLine(thisCouldBeNull.GetValueOrDefault());
+
+// the actual type of int? is Nullable<int>
+Nullable<int> thisCouldAlsoBeNull = null;
+thisCouldAlsoBeNull = 9;
+WriteLine(thisCouldAlsoBeNull);
+
+// Declaring non-nullable variables and parameters
+
+Address address = new();
+address.Building = null;
+address.Street = null!; // null-forgiving operator
+address.City = "London";
+address.Region = "UK";
+
+WriteLine(address.Building?.Length);
+WriteLine(address.Street.Length);

vs4win/Chapter06/PacktLibrary/DisplacementVector.cs

@@ -0,0 +1,22 @@
+namespace Packt.Shared;
+
+public struct DisplacementVector
+{
+  public int X { get; set; }
+  public int Y { get; set; }
+
+  public DisplacementVector(int initialX, int initialY)
+  {
+    X = initialX;
+    Y = initialY;
+  }
+
+  public static DisplacementVector operator +(
+    DisplacementVector vector1,
+    DisplacementVector vector2)
+  {
+    return new(
+      vector1.X + vector2.X,
+      vector1.Y + vector2.Y);
+  }
+}

vs4win/Chapter06/PacktLibrary/DvdPlayer.cs

@@ -0,0 +1,14 @@
+namespace Packt.Shared;
+
+public class DvdPlayer : IPlayable
+{
+  public void Pause()
+  {
+    WriteLine("DVD player is pausing.");
+  }
+
+  public void Play()
+  {
+    WriteLine("DVD player is playing.");
+  }
+}

vs4win/Chapter06/PacktLibrary/Employee.cs

@@ -0,0 +1,22 @@
+namespace Packt.Shared;
+
+public class Employee : Person
+{
+  public string? EmployeeCode { get; set; }
+  public DateTime HireDate { get; set; }
+
+  public new void WriteToConsole()
+  {
+    WriteLine(format:
+      "{0} was born on {1:dd/MM/yy} and hired on {2:dd/MM/yy}",
+      arg0: Name,
+      arg1: DateOfBirth,
+      arg2: HireDate);
+  }
+
+  public override string ToString()
+  {
+    return $"{Name}'s code is {EmployeeCode}";
+  }
+
+}

vs4win/Chapter06/PacktLibrary/IPlayable.cs

@@ -0,0 +1,11 @@
+namespace Packt.Shared;
+
+public interface IPlayable
+{
+  void Play();
+  void Pause();
+  void Stop() // default interface implementation
+  {
+    WriteLine("Default implementation of Stop.");
+  }
+}

vs4win/Chapter06/PacktLibrary/PacktLibrary.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vs4win/Chapter06/PacktLibrary/Person.cs

@@ -0,0 +1,98 @@
+namespace Packt.Shared;
+
+public class Person : object, IComparable<Person?>
+{
+  // properties
+  public string? Name { get; set; }
+  public DateTime DateOfBirth { get; set; }
+
+  // methods
+  public void WriteToConsole()
+  {
+    WriteLine($"{Name} was born on a {DateOfBirth:dddd}.");
+  }
+
+  // delegate field
+  public event EventHandler? Shout;
+
+  // data field
+  public int AngerLevel;
+
+  // method
+  public void Poke()
+  {
+    AngerLevel++;
+    if (AngerLevel >= 3)
+    {
+      /*
+      // if something is listening...
+      if (Shout != null)
+      {
+        // ...then call the delegate
+        Shout(this, EventArgs.Empty);
+      }
+      */
+
+      // simplified syntax available in C# 6 or later
+      Shout?.Invoke(this, EventArgs.Empty);
+    }
+  }
+
+  public int CompareTo(Person? other)
+  {
+    int position;
+    if ((this is not null) && (other is not null))
+    {
+      if ((Name is not null) && (other.Name is not null))
+      {
+        // if both Name values are not null,
+        // use the string implementation of CompareTo
+        position = Name.CompareTo(other.Name);
+      }
+      else if ((Name is not null) && (other.Name is null))
+      {
+        position = -1; // else this Person precedes other Person
+      }
+      else if ((Name is null) && (other.Name is not null))
+      {
+        position = 1; // else this Person follows other Person
+      }
+      else
+      {
+        position = 0; // this Person and other Person are at same position
+      }
+    }
+    else if ((this is not null) && (other is null))
+    {
+      position = -1; // this Person precedes other Person
+    }
+    else if ((this is null) && (other is not null))
+    {
+      position = 1; // this Person follows other Person
+    }
+    else
+    {
+      position = 0; // this Person and other Person are at same position
+    }
+    return position;
+  }
+
+  // overridden methods
+  public override string ToString()
+  {
+    return $"{Name} is a {base.ToString()}";
+  }
+
+  public void TimeTravel(DateTime when)
+  {
+    if (when <= DateOfBirth)
+    {
+      throw new PersonException("If you travel back in time to a date earlier than your own birth, then the universe will explode!");
+    }
+    else
+    {
+      WriteLine($"Welcome to {when:yyyy}!");
+    }
+  }
+
+}

vs4win/Chapter06/PacktLibrary/PersonComparer.cs

@@ -0,0 +1,56 @@
+namespace Packt.Shared;
+
+public class PersonComparer : IComparer<Person?>
+{
+  public int Compare(Person? x, Person? y)
+  {
+    int position;
+    if ((x is not null) && (y is not null))
+    {
+      if ((x.Name is not null) && (y.Name is not null))
+      {
+        // if both Name values are not null...
+
+        // ...compare the Name lengths...
+        int result = x.Name.Length.CompareTo(y.Name.Length);
+
+        /// ...if they are equal... 
+        if (result == 0)
+        {
+          // ...then compare by the Names...
+          return x.Name.CompareTo(y.Name);
+        }
+        else
+        {
+          // ...otherwise compare by the lengths.
+          position = result;
+        }
+      }
+      else if ((x.Name is not null) && (y.Name is null))
+      {
+        position = -1; // else x Person precedes y Person
+      }
+      else if ((x.Name is null) && (y.Name is not null))
+      {
+        position = 1; // else x Person follows y Person
+      }
+      else
+      {
+        position = 0; // x Person and y Person are at same position
+      }
+    }
+    else if ((x is not null) && (y is null))
+    {
+      position = -1; // x Person precedes y Person
+    }
+    else if ((x is null) && (y is not null))
+    {
+      position = 1; // x Person follows y Person
+    }
+    else
+    {
+      position = 0; // x Person and y Person are at same position
+    }
+    return position;
+  }
+}

vs4win/Chapter06/PacktLibrary/PersonException.cs

@@ -0,0 +1,11 @@
+namespace Packt.Shared;
+
+public class PersonException : Exception
+{
+  public PersonException() : base() { }
+
+  public PersonException(string message) : base(message) { }
+
+  public PersonException(string message, Exception innerException)
+    : base(message, innerException) { }
+}

vs4win/Chapter06/PacktLibrary/StringExtensions.cs

@@ -0,0 +1,15 @@
+using System.Text.RegularExpressions; // to get Regex
+
+namespace Packt.Shared;
+
+public static class StringExtensions
+{
+  public static bool IsValidEmail(this string input)
+  {
+    // use a simple regular expression to check
+    // that the input string is a valid email
+
+    return Regex.IsMatch(input,
+      @"[a-zA-Z0-9\.-_]+@[a-zA-Z0-9\.-_]+");
+  }
+}

vs4win/Chapter06/PeopleApp/PeopleApp.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+	  <Using Include="System.Console" Static="true" />
+  </ItemGroup>
+
+	<ItemGroup>
+		<ProjectReference
+			Include="..\PacktLibrary\PacktLibrary.csproj" />
+	</ItemGroup>
+
+</Project>

vs4win/Chapter06/PeopleApp/Program.EventHandlers.cs

@@ -0,0 +1,24 @@
+using Packt.Shared;
+
+partial class Program
+{
+  // a method to handle the Shout event received by the harry object
+  static void Harry_Shout(object? sender, EventArgs e)
+  {
+    if (sender is null) return;
+    Person? p = sender as Person;
+    if (p is null) return;
+
+    WriteLine($"{p.Name} is this angry: {p.AngerLevel}.");
+  }
+
+  // another method to handle the Shout event received by the harry object
+  static void Harry_Shout2(object? sender, EventArgs e)
+  {
+    if (sender is null) return;
+    Person? p = sender as Person;
+    if (p is null) return;
+
+    WriteLine($"Stop it!");
+  }
+}

vs4win/Chapter06/PeopleApp/Program.Helpers.cs

@@ -0,0 +1,19 @@
+using Packt.Shared;
+
+partial class Program
+{
+  static void OutputPeopleNames(IEnumerable<Person?> people, string title)
+  {
+    WriteLine(title);
+    foreach (Person? p in people)
+    {
+      WriteLine("  {0}",
+        p is null ? "<null> Person" : p.Name ?? "<null> Name");
+
+
+      /* if p is null then output: <null> Person
+         else output: p.Name
+         unless p.Name is null in which case output: <null> Name */
+    }
+  }
+}

vs4win/Chapter06/PeopleApp/Program.cs

@@ -0,0 +1,184 @@
+using Packt.Shared;
+
+Person harry = new()
+{
+  Name = "Harry",
+  DateOfBirth = new(year: 2001, month: 3, day: 25)
+};
+
+harry.WriteToConsole();
+
+// non-generic lookup collection
+System.Collections.Hashtable lookupObject = new();
+lookupObject.Add(key: 1, value: "Alpha");
+lookupObject.Add(key: 2, value: "Beta");
+lookupObject.Add(key: 3, value: "Gamma");
+lookupObject.Add(key: harry, value: "Delta");
+
+int key = 2; // lookup the value that has 2 as its key
+
+WriteLine(format: "Key {0} has value: {1}",
+  arg0: key,
+  arg1: lookupObject[key]);
+
+// lookup the value that has harry as its key
+WriteLine(format: "Key {0} has value: {1}",
+  arg0: harry,
+  arg1: lookupObject[harry]);
+
+// generic lookup collection
+Dictionary<int, string> lookupIntString = new();
+lookupIntString.Add(key: 1, value: "Alpha");
+lookupIntString.Add(key: 2, value: "Beta");
+lookupIntString.Add(key: 3, value: "Gamma");
+lookupIntString.Add(key: 4, value: "Delta");
+
+key = 3;
+
+WriteLine(format: "Key {0} has value: {1}",
+  arg0: key,
+  arg1: lookupIntString[key]);
+
+// Defining and handling delegates
+
+// assign event handler methods to Shout event
+harry.Shout += Harry_Shout;
+harry.Shout += Harry_Shout2;
+
+// call the Poke method that raises the Shout event
+harry.Poke();
+harry.Poke();
+harry.Poke();
+harry.Poke();
+
+// Comparing objects when sorting
+
+Person?[] people =
+{
+  null,
+  new() { Name = "Simon" },
+  new() { Name = "Jenny" },
+  new() { Name = "Adam" },
+  new() { Name = null },
+  new() { Name = "Richard" }
+};
+
+OutputPeopleNames(people, "Initial list of people:");
+
+Array.Sort(people);
+
+OutputPeopleNames(people, 
+  "After sorting using Person's IComparable implementation:");
+
+Array.Sort(people, new PersonComparer());
+
+OutputPeopleNames(people,
+  "After sorting using PersonComparer's IComparer implementation:");
+
+// Equality of types
+
+int a = 3;
+int b = 3;
+WriteLine($"a: {a}, b: {b}");
+WriteLine($"a == b: {(a == b)}");
+
+Person p1 = new() { Name = "Kevin" };
+Person p2 = new() { Name = "Kevin" };
+WriteLine($"p1: {p1}, p2: {p2}");
+WriteLine($"p1 == p2: {(p1 == p2)}");
+
+Person p3 = p1;
+WriteLine($"p3: {p3}");
+WriteLine($"p1 == p3: {(p1 == p3)}");
+
+WriteLine($"p1.Name: {p1.Name}, p2.Name: {p2.Name}");
+WriteLine($"p1.Name == p2.Name: {(p1.Name == p2.Name)}");
+
+// Defining struct types
+
+DisplacementVector dv1 = new(3, 5);
+DisplacementVector dv2 = new(-2, 7);
+DisplacementVector dv3 = dv1 + dv2;
+WriteLine($"({dv1.X}, {dv1.Y}) + ({dv2.X}, {dv2.Y}) = ({dv3.X}, {dv3.Y})");
+
+DisplacementVector dv4 = new();
+WriteLine($"({dv4.X}, {dv4.Y})");
+
+// Inheriting from classes
+
+Employee john = new()
+{
+  Name = "John Jones",
+  DateOfBirth = new(year: 1990, month: 7, day: 28)
+};
+john.WriteToConsole();
+
+john.EmployeeCode = "JJ001";
+john.HireDate = new(year: 2014, month: 11, day: 23);
+WriteLine($"{john.Name} was hired on {john.HireDate:dd/MM/yy}");
+
+WriteLine(john.ToString());
+
+Employee aliceInEmployee = new()
+{ Name = "Alice", EmployeeCode = "AA123" };
+
+Person aliceInPerson = aliceInEmployee;
+aliceInEmployee.WriteToConsole();
+aliceInPerson.WriteToConsole();
+WriteLine(aliceInEmployee.ToString());
+WriteLine(aliceInPerson.ToString());
+
+if (aliceInPerson is Employee)
+{
+  WriteLine($"{nameof(aliceInPerson)} IS an Employee");
+
+  Employee explicitAlice = (Employee)aliceInPerson;
+
+  // safely do something with explicitAlice
+}
+
+/* alternative syntax
+if (aliceInPerson is Employee explicitAlice)  
+{
+  WriteLine($"{nameof(aliceInPerson)} IS an Employee"); 
+  // safely do something with explicitAlice
+}
+ */
+
+Employee? aliceAsEmployee = aliceInPerson as Employee; // could be null
+
+if (aliceAsEmployee is not null)
+{
+  WriteLine($"{nameof(aliceInPerson)} AS an Employee");
+
+  // safely do something with aliceAsEmployee
+}
+
+try
+{
+  john.TimeTravel(when: new(1999, 12, 31));
+  john.TimeTravel(when: new(1950, 12, 25));
+}
+catch (PersonException ex)
+{
+  WriteLine(ex.Message);
+}
+
+string email1 = "pamela@test.com";
+string email2 = "ian&test.com";
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email1,
+  arg1: StringExtensions.IsValidEmail(email1));
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email2,
+  arg1: StringExtensions.IsValidEmail(email2));
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email1,
+  arg1: email1.IsValidEmail());
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email2,
+  arg1: email2.IsValidEmail());

vscode/Chapter05/Chapter05.code-workspace

@@ -5,6 +5,9 @@
 		},
 		{
 			"path": "PeopleApp"
+		},
+		{
+			"path": "Namespaces"
 		}
 	]
 }

vscode/Chapter05/Namespaces/France.Paris.cs

@@ -0,0 +1,6 @@
+namespace France
+{
+  public class Paris
+  {
+  }
+}

vscode/Chapter05/Namespaces/Namespaces.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vscode/Chapter05/Namespaces/Program.cs

@@ -0,0 +1,10 @@
+using France;
+using us = Texas; // us becomes alias for the namespace and it is not imported
+using Env = System.Environment;
+
+Paris p1 = new();
+us.Paris p2 = new();
+
+WriteLine(Env.OSVersion);
+WriteLine(Env.MachineName);
+WriteLine(Env.CurrentDirectory);

vscode/Chapter05/Namespaces/Texas.Paris.cs

@@ -0,0 +1,6 @@
+namespace Texas
+{
+  public class Paris
+  {
+  }
+}

vscode/Chapter06/Ch06Ex02Inheritance/Ch06Ex02Inheritance.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vscode/Chapter06/Ch06Ex02Inheritance/Circle.cs

@@ -0,0 +1,29 @@
+namespace Packt.Shared;
+
+public class Circle : Square
+{
+  public Circle() { }
+
+  public Circle(double radius) : base(width: radius * 2) { }
+
+  public double Radius
+  {
+    get
+    {
+      return height / 2;
+    }
+    set
+    {
+      Height = value * 2;
+    }
+  }
+
+  public override double Area
+  {
+    get
+    {
+      double radius = height / 2;
+      return Math.PI * radius * radius;
+    }
+  }
+}

vscode/Chapter06/Ch06Ex02Inheritance/Program.cs

@@ -0,0 +1,10 @@
+using Packt.Shared;
+
+Rectangle r = new(height: 3, width: 4.5);
+WriteLine($"Rectangle H: {r.Height}, W: {r.Width}, Area: {r.Area}");
+
+Square s = new(5);
+WriteLine($"Square    H: {s.Height}, W: {s.Width}, Area: {s.Area}");
+
+Circle c = new(radius: 2.5);
+WriteLine($"Circle    H: {c.Height}, W: {c.Width}, Area: {c.Area}");

vscode/Chapter06/Ch06Ex02Inheritance/Rectangle.cs

@@ -0,0 +1,20 @@
+namespace Packt.Shared;
+
+public class Rectangle : Shape
+{
+  public Rectangle() { }
+
+  public Rectangle(double height, double width)
+  {
+    this.height = height;
+    this.width = width;
+  }
+
+  public override double Area
+  {
+    get
+    {
+      return height * width;
+    }
+  }
+}

vscode/Chapter06/Ch06Ex02Inheritance/Shape.cs

@@ -0,0 +1,37 @@
+namespace Packt.Shared;
+
+public abstract class Shape
+{
+  // fields
+  protected double height;
+  protected double width;
+
+  // properties
+  public virtual double Height
+  {
+    get
+    {
+      return height;
+    }
+    set
+    {
+      height = value;
+    }
+  }
+
+  public virtual double Width
+  {
+    get
+    {
+      return width;
+    }
+    set
+    {
+      width = value;
+    }
+  }
+
+  // Area must be implemented by derived classes
+  // as a read-only property
+  public abstract double Area { get; }
+}

vscode/Chapter06/Ch06Ex02Inheritance/Square.cs

@@ -0,0 +1,26 @@
+namespace Packt.Shared;
+
+public class Square : Rectangle
+{
+  public Square() { }
+
+  public Square(double width) : base(height: width, width: width) { }
+
+  public override double Height
+  {
+    set
+    {
+      height = value;
+      width = value;
+    }
+  }
+
+  public override double Width
+  {
+    set
+    {
+      height = value;
+      width = value;
+    }
+  }
+}

vscode/Chapter06/Chapter06.code-workspace

@@ -0,0 +1,19 @@
+{
+	"folders": [
+		{
+			"path": "PacktLibrary"
+		},
+		{
+			"path": "PeopleApp"
+		},
+		{
+			"path": "NullHandling"
+		},
+		{
+			"path": "CodeAnalyzing"
+		},
+		{
+			"path": "Ch06Ex02Inheritance"
+		}
+	]
+}

vscode/Chapter06/CodeAnalyzing/CodeAnalyzing.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+		<GenerateDocumentationFile>true</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.406">
+      <PrivateAssets>all</PrivateAssets>
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+    </PackageReference>
+  </ItemGroup>
+
+	<ItemGroup>
+		<None Remove="stylecop.json" />
+	</ItemGroup>
+
+	<ItemGroup>
+		<AdditionalFiles Include="stylecop.json" />
+	</ItemGroup>
+
+</Project>

vscode/Chapter06/CodeAnalyzing/Program.cs

@@ -0,0 +1,23 @@
+// <copyright file="Program.cs" company="Packt">
+// Copyright (c) Packt. All rights reserved.
+// </copyright>
+namespace CodeAnalyzing;
+
+using System.Diagnostics;
+
+/// <summary>
+/// The main class for this console app.
+/// </summary>
+public class Program
+{
+  /// <summary>
+  /// The main entry point for this console app.
+  /// </summary>
+  /// <param name="args">
+  /// A string array of arguments passed to the console app.
+  /// </param>
+  public static void Main(string[] args)
+  {
+    Debug.WriteLine("Hello, Debugger!");
+  }
+}

vscode/Chapter06/CodeAnalyzing/stylecop.json

@@ -0,0 +1,12 @@
+{
+  "$schema": "https://raw.githubusercontent.com/DotNetAnalyzers/StyleCopAnalyzers/master/StyleCop.Analyzers/StyleCop.Analyzers/Settings/stylecop.schema.json",
+  "settings": {
+    "orderingRules": {
+      "usingDirectivesPlacement": "preserve"
+    },
+    "documentationRules": {
+      "companyName": "Packt",
+      "copyrightText": "Copyright (c) Packt. All rights reserved."
+    }
+  }
+}

vscode/Chapter06/NullHandling/Address.cs

@@ -0,0 +1,7 @@
+public class Address
+{
+  public string? Building;
+  public string Street = string.Empty;
+  public string City = string.Empty;
+  public string Region = string.Empty;
+}

vscode/Chapter06/NullHandling/NullHandling.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vscode/Chapter06/NullHandling/Program.cs

@@ -0,0 +1,29 @@
+int thisCannotBeNull = 4;
+//thisCannotBeNull = null; // compile error!
+WriteLine(thisCannotBeNull);
+
+int? thisCouldBeNull = null;
+
+WriteLine(thisCouldBeNull);
+WriteLine(thisCouldBeNull.GetValueOrDefault());
+
+thisCouldBeNull = 7;
+
+WriteLine(thisCouldBeNull);
+WriteLine(thisCouldBeNull.GetValueOrDefault());
+
+// the actual type of int? is Nullable<int>
+Nullable<int> thisCouldAlsoBeNull = null;
+thisCouldAlsoBeNull = 9;
+WriteLine(thisCouldAlsoBeNull);
+
+// Declaring non-nullable variables and parameters
+
+Address address = new();
+address.Building = null;
+address.Street = null!; // null-forgiving operator
+address.City = "London";
+address.Region = "UK";
+
+WriteLine(address.Building?.Length);
+WriteLine(address.Street.Length);

vscode/Chapter06/PacktLibrary/DisplacementVector.cs

@@ -0,0 +1,22 @@
+namespace Packt.Shared;
+
+public struct DisplacementVector
+{
+  public int X { get; set; }
+  public int Y { get; set; }
+
+  public DisplacementVector(int initialX, int initialY)
+  {
+    X = initialX;
+    Y = initialY;
+  }
+
+  public static DisplacementVector operator +(
+    DisplacementVector vector1,
+    DisplacementVector vector2)
+  {
+    return new(
+      vector1.X + vector2.X,
+      vector1.Y + vector2.Y);
+  }
+}

vscode/Chapter06/PacktLibrary/DvdPlayer.cs

@@ -0,0 +1,14 @@
+namespace Packt.Shared;
+
+public class DvdPlayer : IPlayable
+{
+  public void Pause()
+  {
+    WriteLine("DVD player is pausing.");
+  }
+
+  public void Play()
+  {
+    WriteLine("DVD player is playing.");
+  }
+}

vscode/Chapter06/PacktLibrary/Employee.cs

@@ -0,0 +1,22 @@
+namespace Packt.Shared;
+
+public class Employee : Person
+{
+  public string? EmployeeCode { get; set; }
+  public DateTime HireDate { get; set; }
+
+  public new void WriteToConsole()
+  {
+    WriteLine(format:
+      "{0} was born on {1:dd/MM/yy} and hired on {2:dd/MM/yy}",
+      arg0: Name,
+      arg1: DateOfBirth,
+      arg2: HireDate);
+  }
+
+  public override string ToString()
+  {
+    return $"{Name}'s code is {EmployeeCode}";
+  }
+
+}

vscode/Chapter06/PacktLibrary/IPlayable.cs

@@ -0,0 +1,11 @@
+namespace Packt.Shared;
+
+public interface IPlayable
+{
+  void Play();
+  void Pause();
+  void Stop() // default interface implementation
+  {
+    WriteLine("Default implementation of Stop.");
+  }
+}

vscode/Chapter06/PacktLibrary/PacktLibrary.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+	<ItemGroup>
+		<Using Include="System.Console" Static="true" />
+	</ItemGroup>
+
+</Project>

vscode/Chapter06/PacktLibrary/Person.cs

@@ -0,0 +1,98 @@
+namespace Packt.Shared;
+
+public class Person : object, IComparable<Person?>
+{
+  // properties
+  public string? Name { get; set; }
+  public DateTime DateOfBirth { get; set; }
+
+  // methods
+  public void WriteToConsole()
+  {
+    WriteLine($"{Name} was born on a {DateOfBirth:dddd}.");
+  }
+
+  // delegate field
+  public event EventHandler? Shout;
+
+  // data field
+  public int AngerLevel;
+
+  // method
+  public void Poke()
+  {
+    AngerLevel++;
+    if (AngerLevel >= 3)
+    {
+      /*
+      // if something is listening...
+      if (Shout != null)
+      {
+        // ...then call the delegate
+        Shout(this, EventArgs.Empty);
+      }
+      */
+
+      // simplified syntax available in C# 6 or later
+      Shout?.Invoke(this, EventArgs.Empty);
+    }
+  }
+
+  public int CompareTo(Person? other)
+  {
+    int position;
+    if ((this is not null) && (other is not null))
+    {
+      if ((Name is not null) && (other.Name is not null))
+      {
+        // if both Name values are not null,
+        // use the string implementation of CompareTo
+        position = Name.CompareTo(other.Name);
+      }
+      else if ((Name is not null) && (other.Name is null))
+      {
+        position = -1; // else this Person precedes other Person
+      }
+      else if ((Name is null) && (other.Name is not null))
+      {
+        position = 1; // else this Person follows other Person
+      }
+      else
+      {
+        position = 0; // this Person and other Person are at same position
+      }
+    }
+    else if ((this is not null) && (other is null))
+    {
+      position = -1; // this Person precedes other Person
+    }
+    else if ((this is null) && (other is not null))
+    {
+      position = 1; // this Person follows other Person
+    }
+    else
+    {
+      position = 0; // this Person and other Person are at same position
+    }
+    return position;
+  }
+
+  // overridden methods
+  public override string ToString()
+  {
+    return $"{Name} is a {base.ToString()}";
+  }
+
+  public void TimeTravel(DateTime when)
+  {
+    if (when <= DateOfBirth)
+    {
+      throw new PersonException("If you travel back in time to a date earlier than your own birth, then the universe will explode!");
+    }
+    else
+    {
+      WriteLine($"Welcome to {when:yyyy}!");
+    }
+  }
+
+}

vscode/Chapter06/PacktLibrary/PersonComparer.cs

@@ -0,0 +1,56 @@
+namespace Packt.Shared;
+
+public class PersonComparer : IComparer<Person?>
+{
+  public int Compare(Person? x, Person? y)
+  {
+    int position;
+    if ((x is not null) && (y is not null))
+    {
+      if ((x.Name is not null) && (y.Name is not null))
+      {
+        // if both Name values are not null...
+
+        // ...compare the Name lengths...
+        int result = x.Name.Length.CompareTo(y.Name.Length);
+
+        /// ...if they are equal... 
+        if (result == 0)
+        {
+          // ...then compare by the Names...
+          return x.Name.CompareTo(y.Name);
+        }
+        else
+        {
+          // ...otherwise compare by the lengths.
+          position = result;
+        }
+      }
+      else if ((x.Name is not null) && (y.Name is null))
+      {
+        position = -1; // else x Person precedes y Person
+      }
+      else if ((x.Name is null) && (y.Name is not null))
+      {
+        position = 1; // else x Person follows y Person
+      }
+      else
+      {
+        position = 0; // x Person and y Person are at same position
+      }
+    }
+    else if ((x is not null) && (y is null))
+    {
+      position = -1; // x Person precedes y Person
+    }
+    else if ((x is null) && (y is not null))
+    {
+      position = 1; // x Person follows y Person
+    }
+    else
+    {
+      position = 0; // x Person and y Person are at same position
+    }
+    return position;
+  }
+}

vscode/Chapter06/PacktLibrary/PersonException.cs

@@ -0,0 +1,11 @@
+namespace Packt.Shared;
+
+public class PersonException : Exception
+{
+  public PersonException() : base() { }
+
+  public PersonException(string message) : base(message) { }
+
+  public PersonException(string message, Exception innerException)
+    : base(message, innerException) { }
+}

vscode/Chapter06/PacktLibrary/StringExtensions.cs

@@ -0,0 +1,15 @@
+using System.Text.RegularExpressions; // to get Regex
+
+namespace Packt.Shared;
+
+public static class StringExtensions
+{
+  public static bool IsValidEmail(this string input)
+  {
+    // use a simple regular expression to check
+    // that the input string is a valid email
+
+    return Regex.IsMatch(input,
+      @"[a-zA-Z0-9\.-_]+@[a-zA-Z0-9\.-_]+");
+  }
+}

vscode/Chapter06/PeopleApp/PeopleApp.csproj

@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net7.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+  <ItemGroup>
+	  <Using Include="System.Console" Static="true" />
+  </ItemGroup>
+
+	<ItemGroup>
+		<ProjectReference
+			Include="..\PacktLibrary\PacktLibrary.csproj" />
+	</ItemGroup>
+
+</Project>

vscode/Chapter06/PeopleApp/Program.EventHandlers.cs

@@ -0,0 +1,24 @@
+using Packt.Shared;
+
+partial class Program
+{
+  // a method to handle the Shout event received by the harry object
+  static void Harry_Shout(object? sender, EventArgs e)
+  {
+    if (sender is null) return;
+    Person? p = sender as Person;
+    if (p is null) return;
+
+    WriteLine($"{p.Name} is this angry: {p.AngerLevel}.");
+  }
+
+  // another method to handle the Shout event received by the harry object
+  static void Harry_Shout2(object? sender, EventArgs e)
+  {
+    if (sender is null) return;
+    Person? p = sender as Person;
+    if (p is null) return;
+
+    WriteLine($"Stop it!");
+  }
+}

vscode/Chapter06/PeopleApp/Program.Helpers.cs

@@ -0,0 +1,19 @@
+using Packt.Shared;
+
+partial class Program
+{
+  static void OutputPeopleNames(IEnumerable<Person?> people, string title)
+  {
+    WriteLine(title);
+    foreach (Person? p in people)
+    {
+      WriteLine("  {0}",
+        p is null ? "<null> Person" : p.Name ?? "<null> Name");
+
+
+      /* if p is null then output: <null> Person
+         else output: p.Name
+         unless p.Name is null in which case output: <null> Name */
+    }
+  }
+}

vscode/Chapter06/PeopleApp/Program.cs

@@ -0,0 +1,184 @@
+using Packt.Shared;
+
+Person harry = new()
+{
+  Name = "Harry",
+  DateOfBirth = new(year: 2001, month: 3, day: 25)
+};
+
+harry.WriteToConsole();
+
+// non-generic lookup collection
+System.Collections.Hashtable lookupObject = new();
+lookupObject.Add(key: 1, value: "Alpha");
+lookupObject.Add(key: 2, value: "Beta");
+lookupObject.Add(key: 3, value: "Gamma");
+lookupObject.Add(key: harry, value: "Delta");
+
+int key = 2; // lookup the value that has 2 as its key
+
+WriteLine(format: "Key {0} has value: {1}",
+  arg0: key,
+  arg1: lookupObject[key]);
+
+// lookup the value that has harry as its key
+WriteLine(format: "Key {0} has value: {1}",
+  arg0: harry,
+  arg1: lookupObject[harry]);
+
+// generic lookup collection
+Dictionary<int, string> lookupIntString = new();
+lookupIntString.Add(key: 1, value: "Alpha");
+lookupIntString.Add(key: 2, value: "Beta");
+lookupIntString.Add(key: 3, value: "Gamma");
+lookupIntString.Add(key: 4, value: "Delta");
+
+key = 3;
+
+WriteLine(format: "Key {0} has value: {1}",
+  arg0: key,
+  arg1: lookupIntString[key]);
+
+// Defining and handling delegates
+
+// assign event handler methods to Shout event
+harry.Shout += Harry_Shout;
+harry.Shout += Harry_Shout2;
+
+// call the Poke method that raises the Shout event
+harry.Poke();
+harry.Poke();
+harry.Poke();
+harry.Poke();
+
+// Comparing objects when sorting
+
+Person?[] people =
+{
+  null,
+  new() { Name = "Simon" },
+  new() { Name = "Jenny" },
+  new() { Name = "Adam" },
+  new() { Name = null },
+  new() { Name = "Richard" }
+};
+
+OutputPeopleNames(people, "Initial list of people:");
+
+Array.Sort(people);
+
+OutputPeopleNames(people, 
+  "After sorting using Person's IComparable implementation:");
+
+Array.Sort(people, new PersonComparer());
+
+OutputPeopleNames(people,
+  "After sorting using PersonComparer's IComparer implementation:");
+
+// Equality of types
+
+int a = 3;
+int b = 3;
+WriteLine($"a: {a}, b: {b}");
+WriteLine($"a == b: {(a == b)}");
+
+Person p1 = new() { Name = "Kevin" };
+Person p2 = new() { Name = "Kevin" };
+WriteLine($"p1: {p1}, p2: {p2}");
+WriteLine($"p1 == p2: {(p1 == p2)}");
+
+Person p3 = p1;
+WriteLine($"p3: {p3}");
+WriteLine($"p1 == p3: {(p1 == p3)}");
+
+WriteLine($"p1.Name: {p1.Name}, p2.Name: {p2.Name}");
+WriteLine($"p1.Name == p2.Name: {(p1.Name == p2.Name)}");
+
+// Defining struct types
+
+DisplacementVector dv1 = new(3, 5);
+DisplacementVector dv2 = new(-2, 7);
+DisplacementVector dv3 = dv1 + dv2;
+WriteLine($"({dv1.X}, {dv1.Y}) + ({dv2.X}, {dv2.Y}) = ({dv3.X}, {dv3.Y})");
+
+DisplacementVector dv4 = new();
+WriteLine($"({dv4.X}, {dv4.Y})");
+
+// Inheriting from classes
+
+Employee john = new()
+{
+  Name = "John Jones",
+  DateOfBirth = new(year: 1990, month: 7, day: 28)
+};
+john.WriteToConsole();
+
+john.EmployeeCode = "JJ001";
+john.HireDate = new(year: 2014, month: 11, day: 23);
+WriteLine($"{john.Name} was hired on {john.HireDate:dd/MM/yy}");
+
+WriteLine(john.ToString());
+
+Employee aliceInEmployee = new()
+{ Name = "Alice", EmployeeCode = "AA123" };
+
+Person aliceInPerson = aliceInEmployee;
+aliceInEmployee.WriteToConsole();
+aliceInPerson.WriteToConsole();
+WriteLine(aliceInEmployee.ToString());
+WriteLine(aliceInPerson.ToString());
+
+if (aliceInPerson is Employee)
+{
+  WriteLine($"{nameof(aliceInPerson)} IS an Employee");
+
+  Employee explicitAlice = (Employee)aliceInPerson;
+
+  // safely do something with explicitAlice
+}
+
+/* alternative syntax
+if (aliceInPerson is Employee explicitAlice)  
+{
+  WriteLine($"{nameof(aliceInPerson)} IS an Employee"); 
+  // safely do something with explicitAlice
+}
+ */
+
+Employee? aliceAsEmployee = aliceInPerson as Employee; // could be null
+
+if (aliceAsEmployee is not null)
+{
+  WriteLine($"{nameof(aliceInPerson)} AS an Employee");
+
+  // safely do something with aliceAsEmployee
+}
+
+try
+{
+  john.TimeTravel(when: new(1999, 12, 31));
+  john.TimeTravel(when: new(1950, 12, 25));
+}
+catch (PersonException ex)
+{
+  WriteLine(ex.Message);
+}
+
+string email1 = "pamela@test.com";
+string email2 = "ian&test.com";
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email1,
+  arg1: StringExtensions.IsValidEmail(email1));
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email2,
+  arg1: StringExtensions.IsValidEmail(email2));
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email1,
+  arg1: email1.IsValidEmail());
+
+WriteLine("{0} is a valid e-mail address: {1}",
+  arg0: email2,
+  arg1: email2.IsValidEmail());