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    <p>Well, first off, what you have there is not an instance of a Strategy pattern. The <a href="http://en.wikipedia.org/wiki/Strategy_pattern" rel="noreferrer">Strategy Pattern</a> allows for the dynamic specification of a method for getting things done. What you have here is really more of a standard interface design, where you allocate responsibilities and abilities by interface inheritance.</p> <p>Edit: Let's use an example. Let's say that you have a group of Workers; you also have a set of Tasks. Each Worker can perform a Task. These Tasks can consist if several things, such as DoFoo() and DoBar(). Each Worker does not know what Task they will perform; they just know when they show up that they will do a Task.</p> <p>So we'll want to model Workers as having a Task that they will perform. Since the Tasks vary widely, we'll implement the Task as an interface.</p> <p>So we'll have:</p> <pre><code>public class Worker { public Task myTask; public Worker(Task task) { myTask = task; } public void DoWork() { myTask.DoTask(); } } } Interface Task { void DoTask(); } public class Task1 : Task { public void DoTask() { // Do whatever Task1 will do } } public class Task2 : Task { public void DoTask() { // Do whatever Task2 will do } } public class Job { public List&lt;Worker&gt; workers; public void Job() { workers.Add(new Worker(new Task1())); workers.Add(new Worker(new Task2())); } public void DoJob() { foreach (Worker worker in workers) { worker.DoWork(); } } public void ChangeJobsToTask1() { foreach (Worker worker in workers) { worker.myTask = new Task1(); } } public void ChangeJobsToTask2() { foreach (Worker worker in workers) { worker.myTask = new Task2(); } } } </code></pre> <p>So what happens is that when we instantiate a <code>Job</code>, the <code>Job</code> creates two <code>Worker</code>s. The first <code>Worker</code> has a <code>Task1</code> task; the second <code>Worker</code> has a <code>Task2</code> task. To make the <code>Worker</code>s do their <code>Task</code>s, we call the <code>DoJob()</code> method on the <code>Job</code> class, which just calls the <code>DoWork()</code> method on each of the <code>Worker</code>s, which in turn calls the <code>DoTask()</code> method on each of the <code>Task</code>s that the <code>Worker</code>s were set with. </p> <p>If we want to change the <code>Worker</code>s to all do <code>Task1</code>, we call the <code>ChangeJobsToTask1()</code> method, which sets the <code>Task</code> to <code>Task1</code> for all of the <code>Worker</code> objects contained by the <code>Job</code>; if, at that point, we call the <code>DoJob()</code> on the <code>Job</code> object, all the <code>Worker</code>s will perform the <code>Task1</code> task. Similarly, if we want to change the <code>Task</code>s to <code>Task2</code>, just call the <code>ChangeJobsToTask2()</code> method; all the <code>Worker</code>s will then execute the <code>Task2.DoTask()</code> when their <code>DoWork()</code> method is called.</p> <p>The important point of abstraction here is that the <code>Worker</code>s expose a <code>DoWork()</code> method, but they do not necessarily know what work it is that is being done. That is, the <code>Task</code>s for the <code>Worker</code>s are interchangeable; the <code>Worker</code>s just know that they're going to do a <code>Task</code>, but the specifics of what it is are unimportant to the <code>Worker</code>s.</p>
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    1. USAndreas Grech
    1. USPaul Sonier
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    1. COFrom the book Head First Design Patterns, I found the principle "Identify the aspects of your application that vary and separate them from what stays the same". Can you suggest me how should I accomplish this?
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    2. CO@JMSA: I can't suggest how to do that without knowing all about your application, but I'll add information to the answer to illustrate an example.
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    3. COFrom all these discussions, I actually found that, my example is not perfect for the Strategy Pattern to be implemented. Isn't it?
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