Practice on Observable and Observer completed

Author: hakanyavaseng

Advanced-C#-Programming/21_IObservable-IObserver/21_IObservable-IObserver.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net8.0</TargetFramework>
+    <RootNamespace>_21_IObservable_IObserver</RootNamespace>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>

Advanced-C#-Programming/21_IObservable-IObserver/Program.cs

@@ -0,0 +1,62 @@
+Console.WriteLine();
+
+#region Practice 1
+
+MyObservable observable = new();
+
+using var sub1 = observable.Subscribe(new MyObserver("1"));
+using var sub2 = observable.Subscribe(new MyObserver("2"));
+using var sub3 = observable.Subscribe(new MyObserver("3"));
+
+observable.NotifyObservers(10);
+observable.NotifyObservers(20);
+observable.NotifyObservers(30);
+
+
+
+class MyObservable : IObservable<int>
+{
+    List<IObserver<int>> observers = new();
+    public IDisposable Subscribe(IObserver<int> observer)
+    {
+        if (!observers.Contains(observer))
+            observers.Add(observer);
+
+        return new Unsubscription(() =>
+        {
+            observers.Remove(observer);
+            observer.OnCompleted();
+        });
+    }
+
+    public void NotifyObservers(int value) => observers.ForEach(observer => observer.OnNext(value));
+}
+
+class Unsubscription(Action unSubscription) : IDisposable
+{
+    public void Dispose()
+    {
+        unSubscription.Invoke();
+        unSubscription = null;
+    }
+}
+
+class MyObserver(string observerName) : IObserver<int>
+{
+    public void OnCompleted()
+    {
+        Console.WriteLine($"{observerName} Completed");
+    }
+
+    public void OnError(Exception error)
+    {
+        Console.WriteLine($"{observerName} Error: {error.Message}");
+    }
+
+    public void OnNext(int value)
+    {
+        Console.WriteLine($"{observerName} Value: {value}");
+    }
+}
+
+#endregion

Advanced-C#-Programming/Advanced-C#-Programming.sln

@@ -39,7 +39,9 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "18_Custom-Collection-Initia
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "19_Attributes", "19_Attributes\19_Attributes.csproj", "{F78E01F6-04B9-4941-B5CF-69013C4921E4}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "20_Reflection", "20_Reflection\20_Reflection.csproj", "{13B7EA4F-231D-4553-BEAC-6A439C1370D6}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "20_Reflection", "20_Reflection\20_Reflection.csproj", "{13B7EA4F-231D-4553-BEAC-6A439C1370D6}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "21_IObservable-IObserver", "21_IObservable-IObserver\21_IObservable-IObserver.csproj", "{B287980D-96C5-47DB-B46B-0A34ACB9C9E7}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -123,6 +125,10 @@ Global
 		{13B7EA4F-231D-4553-BEAC-6A439C1370D6}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{13B7EA4F-231D-4553-BEAC-6A439C1370D6}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{13B7EA4F-231D-4553-BEAC-6A439C1370D6}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B287980D-96C5-47DB-B46B-0A34ACB9C9E7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B287980D-96C5-47DB-B46B-0A34ACB9C9E7}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B287980D-96C5-47DB-B46B-0A34ACB9C9E7}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B287980D-96C5-47DB-B46B-0A34ACB9C9E7}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE