template design pattern

Program.cs

@@ -22,6 +22,7 @@ using design_patterns.behavioral.memento;
 using design_patterns.behavioral.observer;
 using design_patterns.behavioral.state;
 using design_patterns.behavioral.strategy;
+using design_patterns.behavioral.template;
 
 namespace design_patterns
 {
@@ -57,7 +58,8 @@ namespace design_patterns
                 // await MementoSample.Run();
                 // await ObserverSample.Run();
                 // await StateSample.Run();
-                await StrategySample.Run();
+                // await StrategySample.Run();
+                await TemplateSample.Run();
             }
             catch (System.Exception ex)
             {

behavioral/template/TemplateSample.cs

@@ -0,0 +1,98 @@
+using System;
+using System.Threading.Tasks;
+
+namespace design_patterns.behavioral.template
+{
+    /// <summary>
+    /// Template Method is a behavioral design pattern that defines 
+    /// the skeleton of an algorithm in the superclass but lets 
+    /// subclasses override specific steps of the algorithm 
+    /// without changing its structure.
+    /// 
+    /// Use it when:
+    /// - you want to let clients extend only particular steps 
+    ///     of an algorithm, but not the whole algorithm or its structure.
+    /// - you have several classes that contain almost identical algorithms
+    ///     with some minor differences. As a result, you might need to modify 
+    ///     all classes when the algorithm changes.
+    /// </summary>
+    public class TemplateSample
+    {
+        public static async Task Run()
+        {
+            Console.WriteLine("Behavioral - Template");
+            System.Console.WriteLine("Execute Service1");
+            var service1 = new Service1();
+            service1.RunService();
+            System.Console.WriteLine("Execute Service2");
+            var service2 = new Service2();
+            service2.RunService();
+        }
+
+        // template
+        public abstract class AbstractService {
+            public void RunService(){
+                this.BaseOperation1();
+                this.Operation1();
+                this.Operation2();
+                this.Operation3();
+                this.Operation4();
+                this.BaseOperation2();
+            }
+
+            protected void BaseOperation1() {
+                // some base implementation
+                System.Console.WriteLine("Base implementation for BaseOperation1");
+            }
+            protected void BaseOperation2() {
+                // some base implementation
+                System.Console.WriteLine("Base implementation for BaseOperation2");
+            }
+
+            // abstract methods that needs to be implemented by subclasses
+            public abstract void Operation1();
+            public abstract void Operation2();
+
+            // virtual methods that can be overriden by subclasses
+            public virtual void Operation3() {
+                System.Console.WriteLine("Base implementation for Operation3");
+            }
+            public virtual void Operation4() {
+                System.Console.WriteLine("Base implementation for Operation4");
+            }
+        }
+
+        public class Service1 : AbstractService
+        {
+            public override void Operation1()
+            {
+                System.Console.WriteLine("Service1 override for Operation1");
+            }
+
+            public override void Operation2()
+            {
+                System.Console.WriteLine("Service1 override for Operation2");
+            }
+
+            public override void Operation4()
+            {
+                System.Console.WriteLine("Service1 override for Operation4");
+                // can call eventually the base implementation
+                base.Operation4();
+            }
+        }
+
+        public class Service2 : AbstractService
+        {
+            public override void Operation1()
+            {
+                System.Console.WriteLine("Service2 override for Operation1");
+            }
+
+            public override void Operation2()
+            {
+                System.Console.WriteLine("Service2 override for Operation2");
+            }
+        }
+    }
+}