Session 11 content (#53)

* Added Records

* Init samples ready

* Completed demos for session 11

* Added content to README

* Updated with final values from session 11

Author: csharpfritz

sessions/0111-CSharpNine/README.md

@@ -1,9 +1,96 @@
 # Session 11 - New C# v9 Features
 
-With the new release of .NET 5 in November 2020, a new version of the C# programming language was shipped.  Let's take a look at five of the largest updates to the language in this session:
+With the new release of .NET 5 in November 2020, a new version of the C# programming language was shipped labeled C# v9.  Let's take a look at five of the largest updates to the language in this session:
 
 1. Record data types
 1. Init Only Setters
 1. Top Level Programs
 1. Pattern Matching Enhancements
 1. Target-Typed New Expressions
+
+[Official Documentation](https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-9?WT.mc_id=visualstudio-twitch-jefritz) of these updates are available online.
+
+## Record Data Types
+
+Records are a new reference type that synthesizes methods to provide semantics for equality.  Records are immutable (cannot be modified) by default.
+
+The compiler will generate the following methods for you in a record type:
+
+- Methods for value-based equality comparisons
+- GetHasCode()
+- Copy and Clone members
+- `PrintMembers` and `ToString()`
+
+Take a look at the samples in `1-Records.cs` to interact with the `record` keyword and types.
+
+## Init Only Setters
+
+Classes can contain fields marked `readonly` that allow their values to only be set through a constructor.  This can be a bit limiting if you'd like to be able to set values through an intializer in the format:
+
+```csharp
+public class Person {
+    public readonly string FirstName;
+}
+
+var p = new Person {
+    FirstName = "Jeff"
+};
+```
+
+That doesn't work...   neither does this:
+
+```csharp
+public class Person {
+    public string FirstName { get; private set; }
+}
+
+var p = new Person {
+    FirstName = "Jeff"
+};
+```
+
+We can now introduce the `init` scope modifier for a property that allows is to only be set in a constructor OR an initializer.
+
+```csharp
+public class Person {
+    public string FirstName { get; init set; }
+}
+
+var p = new Person {
+    FirstName = "Jeff"
+};
+```
+
+Try out the initializers in `2-Init.cs`
+
+## Top Level Programs
+
+You can now place a file in your project with statements not enclosed in a namespace, a class, or a method.  This can help with not just learning, but running methods quickly in a rapid-development scenario.
+
+```csharp
+System.Console.WriteLine("Hello World");
+```
+
+```dotnetcli
+dotnet watch run
+```
+
+You can reach directly into your application and execute methods on classes.  When you're done testing and tinkering, you can remove the top-level file and everything will continue running with a normal `public static void Main` signature.
+
+## Pattern Matching Enhancements
+
+Pattern matching was a comparison technique introduced in C# 7 that allows you to test the _SHAPE_ of an object in an `if` or `switch` statement.
+
+MORE DOCS ABOUT PATTERN-MATCHING FEATURES
+https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-7?WT.mc_id=visualstudio-twitch-jefritz#pattern-matching
+
+
+https://docs.microsoft.com/en-us/dotnet/csharp/whats-new/csharp-8?WT.mc_id=visualstudio-twitch-jefritz#more-patterns-in-more-places
+
+
+## Target-Typed New Expressions
+
+Constructors can now be simplified when the type is known to just a `new()` statement.
+
+Check the samples in `5-NewTarget.cs`
+

sessions/0111-CSharpNine/SampleConsole/1-Records.cs

@@ -11,7 +11,7 @@ public static void Demo()
 		{
 
 			// Create a record object and inspect its string and equals
-			Demo1();
+			//Demo1();
 
 			// Inheritance with records
 			// Demo2();
@@ -28,14 +28,30 @@ public static void Demo1()
 
 			// Create a new record object and inspect its string
 			var p = new Person("jeff", "fritz");
-			WriteLine(p);
+			// WriteLine(p.FirstName);
+
+			//WriteLine(new PersonClass("jeff","fritz"));
 
 			// Change the record object
 			//p.LastName = "smith";
 
 			// second record equals first
-			// var s = new Person("jeff", "fritz");
-			// WriteLine( p == s);
+			var s = new Person("jeff", "fritz");
+			WriteLine( p == s);
+
+		}
+
+		public class PersonClass {
+			public string FirstName { get; set; }
+			public string LastName { get; set; }
+
+			public override string ToString()
+			{
+				return $"{FirstName} {LastName}";
+			}
+
+			public PersonClass(string first, string last) =>
+			(FirstName, LastName) = (first, last);
 
 		}
 
@@ -59,11 +75,11 @@ public static void Demo2()
 
 			// Records support inheritance
 
-			var p = new CoolPerson("jeff", "fritz");
-			WriteLine(p);
+			// var p = new CoolPerson("jeff", "fritz");
+			// WriteLine(p);
 
 			var r = new Rockstar("Freddie", "Mercury", "Queen");
-			WriteLine(r);
+			// WriteLine(r);
 
 			WriteLine(r as CoolPerson);
 
@@ -85,8 +101,9 @@ public static void Demo3() {
 			WriteLine($"First: {first} Last: {last}");
 
 			// Clone using the WITH expression
-			// var s = p with { FirstName = "scott"};
-			// WriteLine(s);
+			var s = p with { FirstName="scott" };
+			WriteLine(s);
+			WriteLine(p);
 
 		}
 

sessions/0111-CSharpNine/SampleConsole/2-Init.cs

@@ -15,25 +15,23 @@ public static void Demo() {
 
 		public static void Demo1() {
 
-/*
 			var l = new LogEntry {
 				Severity = LogSeverity.Error,
 				LogTimestampUtc = DateTime.UtcNow,
 				Description = "Bad dates..."
 			};
 
 			WriteLine(l);
-*/
 
 		}
 
 		public struct LogEntry {
 
-			public readonly LogSeverity Severity;
+			public LogSeverity Severity {get; init;}
 
-			public readonly DateTime LogTimestampUtc;
+			public DateTime LogTimestampUtc {get; init;}
 
-			public readonly string Description;
+			public string Description {get; init;}
 
 			public override string ToString()
 			{

sessions/0111-CSharpNine/SampleConsole/3-Start.cs

@@ -0,0 +1,9 @@
+/*
+using System;
+using SampleConsole;
+
+Console.WriteLine("This is a top-level program");
+Console.WriteLine($"These are the arguments passed in: {string.Join(',',args)}");
+Records.Demo3();
+
+*/