When Should You Use Delegates in C#?

Application scenarios and advantages of delegation in C#

Delegate is a crucial concept in C# programming. It is a reference to a method. Unlike passing objects directly, delegation allows us to pass methods as parameters to other methods, thereby achieving flexible calls between methods.

Benefits of using delegation:

• Flexibility: Delegates encapsulate methods so that they can be processed like first-class citizens, greatly improving the flexibility of the code.
• Decoupling: Using delegation can decouple the code that calls the method and the code that implements the method, thereby reducing the coupling between codes and improving the maintainability of the code.
• Event handling: The event mechanism in object-oriented programming is implemented based on delegation. This enables asynchronous communication between objects and enables efficient event processing.

Applicable scenarios for delegation:

• When you need to pass a method as a parameter to another method.
• When you need to decouple the code that calls the method and the code that implements the method.
• When implementing events or other callback-based mechanisms.

Necessity of delegation:

Delegates are indispensable when a method needs to be passed as a parameter and there is no other alternative. For example, suppose there is a method for filtering a list of people based on age. To pass this filter as a parameter to another method, we cannot use an object or any other data type; a delegate must be used.

Some code examples:

The following code snippet demonstrates the use of delegates in a simple filtering scenario:

<code class="language-csharp">public delegate bool FilterDelegate(Person p);

static void Main() {
    // 创建人员列表
    List<Person> people = new List<Person>();

    // 使用不同的过滤器委托调用 DisplayPeople
    DisplayPeople("儿童:", people, IsChild);
    DisplayPeople("成年人:", people, IsAdult);
    DisplayPeople("老年人:", people, IsSenior);
}

// 过滤器方法
static bool IsChild(Person p) { return p.Age < 18; }
static bool IsAdult(Person p) { return p.Age >= 18 && p.Age < 65; }
static bool IsSenior(Person p) { return p.Age >= 65; }</code>

This code highlights the power of delegates, which allow us to define filters and pass them as parameters to other methods, allowing for flexible and reusable code design.

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