brought back the original in-memory database as project 00, readme updtd

README.md

@@ -33,30 +33,62 @@ Ideally on my birthday, May 22nd!
 
 ## 🏃 Running
 
-Be sure to launch EventStoreDB through Docker. Through a terminal / command prompt:
+### 0️⃣ Project: StudentEnrollment00
+
+Like the other programs that are .NET console application, the database is a glorified key-value store that's in-memory.
+
+To run it, enter the project directory through your shell's associated Change Directory (`cd`) command from the solution root, such as:
 
 ```bash
-docker-compose up
+cd .\StudentEnrollment01
 ```
 
-You can build the entire solution, including all versions of the projects, by running the following at the root of `/StudentEnrollmentConsoleApp/` with:
+and then build the project
 
 ```bash
 dotnet build
 ```
 
+and run it
+
+```bash
+dotnet run
+```
+
+Alternatively, you can do all this from the solution's root by targeting the project with `--project` and `run` it immediately, such as:
+
+```bash
+dotnet run --project .\StudentEnrollment00\StudentEnrollment00.csproj
+```
+
+### 1️⃣ Project: StudentEnrollment01
+
+While still a .NET console app, we're now going to use the Event Store database. So be sure to launch EventStoreDB through Docker. With a terminal / command prompt execute:
+
+```bash
+docker-compose up
+```
+
+Like before, you can change directory into the project or run it from the root.
+
 Run the console application of your choice, change direction to that particular project directory and then execute:
 
 ```bash
+cd .\StudentEnrollment01
+dotnet build
 dotnet run
 ```
 
-Alternatively, you can stay in the root directory `/StudentEnrollmentConsoleApp/` and include the path to the intended project you want to have run. This same operation can be done with the previous `dotnet build` command, too.
+Or alternatively:
 
 ```bash
-dotnet run .\StudentEnrollment01\StudentEnrollment01.csproj
+dotnet run --project .\StudentEnrollment01\StudentEnrollment01.csproj
 ```
 
+### 2️⃣ TBD
+
+Instructions will go here, but will basically be the same as above!
+
 ## 🔗 Resources
 
 Erik Shafer (me):

StudentEnrollment00/Events/Event.cs

@@ -0,0 +1,8 @@
+namespace StudentEnrollment00.Events;
+
+public abstract class Event
+{
+    public abstract Guid StreamId { get; }
+
+    public DateTime CreatedAtUtc { get; set; }
+}

StudentEnrollment00/Events/StudentCreated.cs

@@ -0,0 +1,11 @@
+namespace StudentEnrollment00.Events;
+
+public class StudentCreated : Event
+{
+    public required Guid StudentId { get; init; }
+    public required string FullName { get; init; }
+    public required string Email { get; init; }
+    public required DateTime DateOfBirth { get; init; }
+
+    public override Guid StreamId => StudentId;
+}

StudentEnrollment00/Events/StudentEnrolled.cs

@@ -0,0 +1,9 @@
+namespace StudentEnrollment00.Events;
+
+public class StudentEnrolled : Event
+{
+    public required Guid StudentId { get; init; }
+    public required string CourseName { get; init; }
+
+    public override Guid StreamId => StudentId;
+}

StudentEnrollment00/Events/StudentUnEnrolled.cs

@@ -0,0 +1,9 @@
+namespace StudentEnrollment00.Events;
+
+public class StudentUnEnrolled : Event
+{
+    public required Guid StudentId { get; init; }
+    public required string CourseName { get; init; }
+
+    public override Guid StreamId => StudentId;
+}

StudentEnrollment00/Events/StudentUpdated.cs

@@ -0,0 +1,10 @@
+namespace StudentEnrollment00.Events;
+
+public class StudentUpdated : Event
+{
+    public required Guid StudentId { get; init; }
+    public required string FullName { get; init; }
+    public required string Email { get; init; }
+
+    public override Guid StreamId => StudentId;
+}

StudentEnrollment00/InMemoryDatabase.cs

@@ -0,0 +1,34 @@
+using StudentEnrollment00.Events;
+
+namespace StudentEnrollment00;
+
+public sealed class InMemoryDatabase
+{
+    private readonly Dictionary<Guid, SortedList<DateTime, Event>> _studentEvents = new();
+
+    public void Append(Event @event)
+    {
+        var stream = _studentEvents!.GetValueOrDefault(@event.StreamId, null);
+        if (stream is null)
+        {
+            _studentEvents[@event.StreamId] = new SortedList<DateTime, Event>();
+        }
+
+        @event.CreatedAtUtc = DateTime.UtcNow;
+        _studentEvents[@event.StreamId].Add(@event.CreatedAtUtc, @event);
+    }
+
+    public Student? GetStudent(Guid id)
+    {
+        if (_studentEvents.ContainsKey(id) is false)
+            return null;
+
+        var student = new Student();
+        var studentEvents = _studentEvents[id];
+
+        foreach (var @event in studentEvents) 
+            student.Apply(@event.Value);
+
+        return student;
+    }
+}

StudentEnrollment00/Program.cs

@@ -0,0 +1,24 @@
+using StudentEnrollment00;
+using StudentEnrollment00.Events;
+
+var id = Guid.Parse("a662d446-4920-415e-8c2a-0dd4a6c58908");
+var now = DateTime.Now;
+
+var studentCreated = new StudentCreated
+{
+    CreatedAtUtc = now.ToUniversalTime(),
+    StudentId = id,
+    FullName = "Erik Shafer",
+    Email = "[email protected]",
+    DateOfBirth = new DateTime(1987, 1, 1)
+};
+
+var inMemoryDb = new InMemoryDatabase();
+inMemoryDb.Append(studentCreated);
+
+var student = inMemoryDb.GetStudent(id);
+
+Console.WriteLine(
+    "StudentId: {0} | FullName: {1} | Email: {2} | DOB: {3} | CreatedAtUtc: {4}", 
+    student!.Id, student.FullName, student.Email, student.DateOfBirth, student.CreatedAtUtc);
+Console.WriteLine();

StudentEnrollment00/Student.cs

@@ -0,0 +1,58 @@
+using StudentEnrollment00.Events;
+
+namespace StudentEnrollment00;
+
+public class Student
+{
+    public Guid Id { get; set; } = default!;
+    public string FullName { get; set; } = default!;
+    public string Email { get; set; } = default!;
+    public DateTime DateOfBirth { get; set; }
+    public DateTime CreatedAtUtc { get; set; }
+    public List<string> EnrolledCourses { get; set; } = [];
+
+    public void Apply(Event @event)
+    {
+        switch (@event)
+        {
+            case StudentCreated created:
+                Apply(created);
+                break;
+            case StudentUpdated updated:
+                Apply(updated);
+                break;
+            case StudentEnrolled enrolled:
+                Apply(enrolled);
+                break;
+            case StudentUnEnrolled unEnrolled:
+                Apply(unEnrolled);
+                break;
+        }
+    }
+
+    private void Apply(StudentCreated @event)
+    {
+        Id = @event.StudentId;
+        FullName = @event.FullName;
+        Email = @event.Email;
+    }
+
+    private void Apply(StudentUpdated @event)
+    {
+        Id = @event.StudentId; // Updating the identity, huh? Interesting... 👀
+        FullName = @event.FullName;
+        Email = @event.Email;
+    }
+
+    private void Apply(StudentEnrolled @event)
+    {
+        if (EnrolledCourses.Contains(@event.CourseName) is false)
+            EnrolledCourses.Add(@event.CourseName);
+    }
+
+    private void Apply(StudentUnEnrolled @event)
+    {
+        if (EnrolledCourses.Contains(@event.CourseName))
+            EnrolledCourses.Add(@event.CourseName);
+    }
+}

StudentEnrollment00/StudentEnrollment00.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net8.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <DockerDefaultTargetOS>Linux</DockerDefaultTargetOS>
+    </PropertyGroup>
+
+</Project>

StudentEnrollment01/Events/Event.cs

@@ -3,4 +3,5 @@ namespace StudentEnrollment01.Events;
 public abstract record Event
 {
     public string Id { get; init; } = default!;
+    public DateTime CreatedAtUtc { get; set; }
 }

StudentEnrollmentConsoleApp.sln

@@ -10,6 +10,8 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution
 		README.md = README.md
 	EndProjectSection
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "StudentEnrollment00", "StudentEnrollment00\StudentEnrollment00.csproj", "{B8D543AF-F986-4E50-AD1D-492B38A58ECF}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -20,5 +22,9 @@ Global
 		{446FF6B7-B58B-4CFB-8E98-C5B3AED9BA4D}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{446FF6B7-B58B-4CFB-8E98-C5B3AED9BA4D}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{446FF6B7-B58B-4CFB-8E98-C5B3AED9BA4D}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B8D543AF-F986-4E50-AD1D-492B38A58ECF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B8D543AF-F986-4E50-AD1D-492B38A58ECF}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B8D543AF-F986-4E50-AD1D-492B38A58ECF}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B8D543AF-F986-4E50-AD1D-492B38A58ECF}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal