75 lines
2.1 KiB
Markdown
75 lines
2.1 KiB
Markdown
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---
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title: Class
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localeTitle: 类
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---
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## 类
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C＃中的类被定义为引用类型。为了使用引用类型实例化变量，必须指定`new`关键字，否则该变量将具有默认值`null` 。请参阅下面的示例。
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```csharp
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// The value of variableOne is null at this point.
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NewClass variableOne;
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// Now the value of variableOne will be an instance of the class NewClass
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variableOne = new NewClass();
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```
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在运行时，在创建类时，将足够的内存分配给堆，以用于该变量保存的类的特定实例。
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#### 创建类
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要在C＃中创建一个类，我们需要使用`class`关键字后跟唯一标识符。
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与其他语言一样，C＃创建一个不接受任何参数的默认构造函数。如果我们需要接受特殊参数或在构造函数中使用自定义initlization步骤，我们也可以指定我们自己的构造函数。
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```csharp
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public class NewClass
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{
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NewClass(string name)
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{
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// Initialization steps...
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}
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}
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```
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类是创建对象的原型或蓝图。在C＃中，使用关键字class定义类。类用于将一些方法，属性，字段，事件和委托组合到一个单元中。类也可以包含嵌套类。
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#### 示例：考虑以下Employee Class的情况：
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```csharp
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using System;
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namespace CPrograms
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{
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class Employee
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{
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private string name;
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private int employeeId;
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public Employee(string name, int employeeId)
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{
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this.name = name;
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this.employeeId = employeeId;
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}
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public void PrintEmployee()
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{
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Console.WriteLine("Employee Name: {0} , Employee ID: {1}", this.name, this.employeeId);
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}
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}
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class Program
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{
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static void Main(string[] args)
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{
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Employee employeeObject = new Employee("John Doe", 420156);
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employeeObject.PrintEmployee();
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}
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}
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}
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```
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类只能从一个基类继承。但是，它可以从多个接口实现。
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## 更多信息
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了解更多关于类[在这里](https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/class)
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