Interface，在C#中是一個(gè)關(guān)鍵字，它包含一組抽象方法和屬性，這些方法和屬性由抽象或非抽象類實(shí)現(xiàn)或使用。定義方法是接口內(nèi)的屬性，默認(rèn)情況下它們是公共和抽象的。

用最簡(jiǎn)單的話來說，接口就像一個(gè)契約，主體中包含的每個(gè)成員或組件都必須遵循契約，它定義了必須做什么。該接口不包含任何字段，并且始終通過使用關(guān)鍵字“interface”來定義。

語(yǔ)法：

語(yǔ)法以接口關(guān)鍵字開頭，后跟接口名稱，然后是正文。

interface <name_for_interface>
{
//abstract methods
//abstract properties.
}

如您所見，我們有 C# 中接口的標(biāo)準(zhǔn)語(yǔ)法，它以“interface”關(guān)鍵字開頭，然后是接口的名稱，然后是主體內(nèi)的抽象方法和屬性。在 C# 中，可以在類或結(jié)構(gòu)內(nèi)部實(shí)現(xiàn)和使用多個(gè)接口。這些接口可以將各種方法、索引器、屬性以及事件作為成員。

為什么我們需要 C# 接口？

基本上我們已經(jīng)明白接口內(nèi)部沒有特定的功能，如果是這樣，那我們?yōu)槭裁葱枰涌冢?/p>

什么時(shí)候使用界面？

• 安全性：?當(dāng)我們必須簡(jiǎn)單地隱藏某些功能并稍后使用它們時(shí)。有必要隱藏一些細(xì)節(jié)，同時(shí)只顯示對(duì)用戶重要的細(xì)節(jié)。
• 多重繼承：在c#中，一個(gè)類可以繼承一個(gè)簡(jiǎn)單的父類，繼承其所有功能。 C# 不支持多重繼承，原因很簡(jiǎn)單，就是為了不讓 C# 變得復(fù)雜。但是通過使用接口，可以將多個(gè)接口實(shí)現(xiàn)到單個(gè)類中。

C# 接口通常包含以下元素：

1. 聲明 – 在 C# 中，接口是定義一組方法簽名、屬性、事件或索引器的契約。它不包含任何實(shí)現(xiàn)，而是作為類要遵循的藍(lán)圖。實(shí)現(xiàn)接口的類必須為接口中聲明的所有成員提供具體的實(shí)現(xiàn)。
2. 成員 – 接口成員是接口內(nèi)聲明的方法、屬性、事件和索引器。他們定義了實(shí)現(xiàn)類必須遵守的契約，以確保不同類之間行為一致。實(shí)現(xiàn)類必須為這些成員提供具體的實(shí)現(xiàn)，促進(jìn)代碼一致性，并實(shí)現(xiàn)多態(tài)性和代碼重用。
3. 實(shí)現(xiàn) – 實(shí)現(xiàn)接口的類必須為接口中聲明的所有成員提供實(shí)現(xiàn)。該類可以使用 :interfaceName 語(yǔ)法顯式指定它實(shí)現(xiàn)一個(gè)接口。例如：

   public class MyClass : IMyInterface
   {
   public void Method1()
   {
   // Method implementation
   }public string Property1 { get; set; }
   
   public event EventHandler Event1;
   }

4. 多重繼承：C# 通過接口支持多重繼承。一個(gè)類可以實(shí)現(xiàn)多個(gè)接口，從而允許它繼承多組方法簽名，而無需與實(shí)現(xiàn)的多重繼承相關(guān)的復(fù)雜性。這使得設(shè)計(jì)類具有更大的靈活性，同時(shí)避免了傳統(tǒng)多重繼承中固有的鉆石問題。
5. 接口繼承：在 C# 中，接口繼承允許派生接口繼承一個(gè)或多個(gè)基接口中定義的方法簽名。實(shí)現(xiàn)派生接口的類必須提供所有繼承方法的實(shí)現(xiàn)。這使得能夠創(chuàng)建接口層次結(jié)構(gòu)，促進(jìn)代碼重用和對(duì)象設(shè)計(jì)的靈活性。

C# 接口示例

現(xiàn)在我們已經(jīng)了解了什么是接口及其需求。讓我們演示一個(gè)帶有接口實(shí)現(xiàn)的 C# 代碼的簡(jiǎn)單示例。

示例#1

程序?qū)崿F(xiàn)接口并打印一條簡(jiǎn)單的語(yǔ)句。

代碼：

using System;
namespace MyApplication {
interface SampleInterface {
void InterfaceMethod();
}
class Int_Example : SampleInterface
{
public void InterfaceMethod() {
Console.WriteLine("\nThis is simple example of Interface in C#.");
}
}
class Program {
static void Main(string[] args) {
Int_Example myInterface = new Int_Example();
myInterface.InterfaceMethod();
Console.Read();
}
}
}

代碼解釋：從使用和命名空間開始，生成一個(gè)基本接口作為 SampleInterface，其主體中有一個(gè)方法。接口內(nèi)的該方法沒有任何特定的主體。然后我們有新的類來實(shí)現(xiàn)我們創(chuàng)建的接口。使用 class 關(guān)鍵字創(chuàng)建，后跟類名，然后使用冒號(hào)符號(hào)后跟接口名稱來實(shí)現(xiàn)接口。在我們的 Int_Example 類中，我們有之前創(chuàng)建的接口方法，當(dāng)時(shí)它還沒有實(shí)體，現(xiàn)在我們添加了簡(jiǎn)單的打印語(yǔ)句，它說：“這是 C# 中接口的一個(gè)簡(jiǎn)單示例?！?/p>

Then begins our mail class, namely Program, with the static void main statement. Inside our main class, we have created a new object for our Int_Example class which inherits interface. The new object is created and to the next line, our method created earlier is called up. Finally, our newly created object will call the earlier created method and the body inside that method will be executed here. With Console.Read(); the program will wait for user input before exiting.

Output:

Upon successful compilation and execution, the program must simply print the statement: “This is a simple example of Interface in C#.”

Example #2

Arithmetic operations using the interface.

Code:

using System;
namespace arth_interface {
public interface SampleInterface {
void sam_add(int a, int b);
void sam_sub(int a, int b);
void display();
}
class interface_class : SampleInterface {
int x, y;
public void sam_add(int a, int b) {
int m, n;
m = a;
n = b;
x = m + n;
}
public void sam_sub(int a, int b) {
int m, n;
m = a;
n = b;
y = a - b;
}
public void display() {
Console.WriteLine("Added Value is:" + x);
Console.WriteLine("Subtracted value is:" + y);
}
}
class arth_interface {
static void Main(string[] args) {
interface_class obj_interface_class = new interface_class();
int fnumber, snumber;
Console.WriteLine("Please Enter 1st Number to perform Addition and Subtraction:");
fnumber = Convert.ToInt16(Console.ReadLine());
Console.WriteLine("Now 2nd Number to perform Addition and Subtraction:");
snumber = Convert.ToInt16(Console.ReadLine());
obj_interface_class.sam_add(fnumber, snumber);
obj_interface_class.sam_sub(fnumber, snumber);
obj_interface_class.display();
Console.ReadKey();
}
}
}

Code Interpretation: Similar to our first example, we have used and namespace statements, followed by the interface and its body with methods. We have two basic methods for addition and subtraction with void as return type, two integers inside every method, respectively. Next, we have our class which implements our interface.

We’ve declared two integers and then we have our first method to calculate addition. Here is the operation that needs to be done for addition and the same is for the subtraction. Then we have our display method, which consists of two print statements, printing addition and subtraction values of the numbers passed.

Finally, we have our class with the main method, where we initially created an object for our interface. Then the program prints “Please Enter the 1st Number to perform Addition and Subtraction:”, where the user inputs a first number and the later second number, for the purpose of calculations. With the object created earlier, the program calls the add and sub-methods from the interface and the same operations are done. At last, we have our display method, which displays our results as defined in the display method and ReadKey(); method holds up our program until any key is pressed.

Output:

Advantages

Below are some of the advantages given.

• One of the major advantages of Interface in C# is a better alternative to implement multiple inheritances.
• The interface enables the plug-and-play method.
• Complete Abstraction can be achieved by the implementation of Interface.
• Along with making our code easy to maintain, concept loose coupling can be achieved.

Conclusion

We have understood what Interface in C# is. The proper syntax for an interface along with an explanation. To wrap it up, Interfaces in C# are a way to fill the emptiness of multiple inheritances in the language. Later we learned why do we actually need the interface in C# followed by the examples to demonstrate the understanding of the interfaces. The first example was to demonstrate simple use of interface while with the second example we implemented arithmetic operations, followed by Code Interpretation and output screenshot.

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