From 74baaf5669bde29c201a0cea4dbc91bbe5a4c611 Mon Sep 17 00:00:00 2001
From: Mark J Price <markjprice@gmail.com>
Date: Thu, 10 Nov 2022 22:01:07 +0000
Subject: [PATCH] Added item for page 244

---
 docs/errata/README.md                         |  2 +-
 docs/errata/errata.md                         |  9 +++++-
 .../Chapter05/PacktLibraryModern/Records.cs   | 18 +++++++++++
 .../PacktLibraryNetStandard2/Records.cs       |  7 -----
 vs4win/Chapter05/PeopleApp/Program.cs         | 31 +++++++++++++++----
 5 files changed, 52 insertions(+), 15 deletions(-)
 create mode 100644 vs4win/Chapter05/PacktLibraryModern/Records.cs
 delete mode 100644 vs4win/Chapter05/PacktLibraryNetStandard2/Records.cs

diff --git a/docs/errata/README.md b/docs/errata/README.md
index e9b32a8..83884ba 100644
--- a/docs/errata/README.md
+++ b/docs/errata/README.md
@@ -2,7 +2,7 @@
 
 If you find any mistakes in the seventh edition, *C# 11 and .NET 7 - Modern Cross-Platform Development Fundamentals*, or if you have suggestions for improvements, then please [raise an issue in this repository](https://github.com/markjprice/cs11dotnet7/issues) or email me at markjprice (at) gmail.com.
 
-[**Errata** (6 items)](errata.md): Typos, tool user interface changes, or mistakes in code that would cause a compilation error that prevents a successful build.
+[**Errata** (7 items)](errata.md): Typos, tool user interface changes, or mistakes in code that would cause a compilation error that prevents a successful build.
 
 [**Improvements** (1 item)](improvements.md): Changes to text or code that would improve the content. These are optional.
 
diff --git a/docs/errata/errata.md b/docs/errata/errata.md
index dd0a6e0..56a68d9 100644
--- a/docs/errata/errata.md
+++ b/docs/errata/errata.md
@@ -1,4 +1,4 @@
-**Errata (6 items)**
+**Errata (7 items)**
 
 If you find any mistakes, then please [raise an issue in this repository](https://github.com/markjprice/cs11dotnet7/issues) or email me at markjprice (at) gmail.com.
 
@@ -10,6 +10,7 @@ If you find any mistakes, then please [raise an issue in this repository](https:
 - [Page 83 - Formatting using numbered positional arguments](#page-83---formatting-using-numbered-positional-arguments)
 - [Page 86 - Getting text input from the user](#page-86---getting-text-input-from-the-user)
 - [Page 188 - Running unit tests using Visual Studio Code](#page-188---running-unit-tests-using-visual-studio-code)
+- [Page 244 - Init-only properties](#page-244---init-only-properties)
 
 # Page 4, 8 - Pros and cons of the .NET Interactive Notebooks extension, Downloading and installing Visual Studio Code
 
@@ -81,3 +82,9 @@ In Step 3, I wrote, "For the `firstName` variable" when I should have written, "
 > Thanks to [kwatsonkairosmgt](https://github.com/kwatsonkairosmgt) for raising this [issue on 27 October 2022](https://github.com/markjprice/cs10dotnet6/issues/106).
 
 In Step 1, the project name `CalculatorLibUnitTest` should be `CalculatorLibUnitTests`.
+
+# Page 244 - Init-only properties
+
+> Thanks to Bob Molloy for raising this issue via email.
+
+In Step 1, I say to add a new file named `Records.cs` to the `PacktLibraryNetStandard2` project/folder. I should have said to the `PacktLibraryModern` project/folder.
diff --git a/vs4win/Chapter05/PacktLibraryModern/Records.cs b/vs4win/Chapter05/PacktLibraryModern/Records.cs
new file mode 100644
index 0000000..096d29d
--- /dev/null
+++ b/vs4win/Chapter05/PacktLibraryModern/Records.cs
@@ -0,0 +1,18 @@
+namespace Packt.Shared;
+
+public class ImmutablePerson
+{
+  public string? FirstName { get; init; }
+  public string? LastName { get; init; }
+}
+
+public record ImmutableVehicle
+{
+  public int Wheels { get; init; }
+  public string? Color { get; init; }
+  public string? Brand { get; init; }
+}
+
+// simpler way to define a record
+// auto-generates the properties, constructor, and deconstructor
+public record ImmutableAnimal(string Name, string Species);
\ No newline at end of file
diff --git a/vs4win/Chapter05/PacktLibraryNetStandard2/Records.cs b/vs4win/Chapter05/PacktLibraryNetStandard2/Records.cs
deleted file mode 100644
index bfb2a46..0000000
--- a/vs4win/Chapter05/PacktLibraryNetStandard2/Records.cs
+++ /dev/null
@@ -1,7 +0,0 @@
-namespace Packt.Shared;
-
-public class ImmutablePerson
-{
-  //public string? FirstName { get; init; }
-  //public string? LastName { get; init; }
-}
diff --git a/vs4win/Chapter05/PeopleApp/Program.cs b/vs4win/Chapter05/PeopleApp/Program.cs
index f80431d..f57c114 100644
--- a/vs4win/Chapter05/PeopleApp/Program.cs
+++ b/vs4win/Chapter05/PeopleApp/Program.cs
@@ -293,9 +293,28 @@ foreach (Passenger passenger in passengers)
   WriteLine($"Flight costs {flightCost:C} for {passenger}");
 }
 
-//ImmutablePerson jeff = new()
-//{
-//  FirstName = "Jeff",
-//  LastName = "Winger"
-//};
-//jeff.FirstName = "Geoff";
+ImmutablePerson jeff = new()
+{
+  FirstName = "Jeff",
+  LastName = "Winger"
+};
+// We cannot set the properties after initialization because they
+// are init-only.
+// jeff.FirstName = "Geoff";
+
+ImmutableVehicle car = new()
+{
+  Brand = "Mazda MX-5 RF",
+  Color = "Soul Red Crystal Metallic",
+  Wheels = 4
+};
+
+ImmutableVehicle repaintedCar = car
+  with { Color = "Polymetal Grey Metallic" };
+
+WriteLine($"Original car color was {car.Color}.");
+WriteLine($"New car color is {repaintedCar.Color}.");
+
+ImmutableAnimal oscar = new("Oscar", "Labrador");
+var (who, what) = oscar; // calls Deconstruct method 
+WriteLine($"{who} is a {what}.");