c# 中的嵌套类
一个类是一个用户定义的蓝图或原型，从它可以创建对象。基本上，一个类将字段和方法(定义动作的成员函数)组合成一个单元。在 C# 中，允许用户在另一个类中定义一个类。这类类被称为嵌套类。该特性使用户能够对仅在一个地方使用的类进行逻辑分组，从而增加了封装的使用，并创建了可读性和可维护性更强的代码。
语法:
class Outer_class {
// Code..
class Inner_class {
// Code..
}
}
示例:
C
// C# program to illustrate the
// concept of nested class
using System;
// Outer class
public class Outer_class {
// Method of outer class
public void method1()
{
Console.WriteLine("Outer class method");
}
// Inner class
public class Inner_class {
// Method of inner class
public void method2()
{
Console.WriteLine("Inner class Method");
}
}
}
// Driver Class
public class GFG {
// Main method
static public void Main()
{
// Create the instance of outer class
Outer_class obj1 = new Outer_class();
obj1.method1();
// This statement gives an error because
// you are not allowed to access inner
// class methods with outer class objects
// obj1\. method2();
// Creating an instance of inner class
Outer_class.Inner_class obj2 =
new Outer_class.Inner_class();
// Accessing the method of inner class
obj2.method2();
}
}
输出:
Outer class method
Inner class Method
要点:
- 嵌套类可以声明为私有、公共、受保护、内部、受保护内部或私有受保护。
- 如上例所示，外部类不允许直接访问内部类成员。
- 您可以在外部类中创建内部类的对象。
- 内部类可以访问外部类中声明的静态成员，如下例所示: 例:
C
// C# program to illustrate the
// concept of nested class accessing
// static members of the outer class
using System;
// Outer class
public class Outer_class {
// Static data member of the outer class
public static string str = "Geeksforgeeks";
// Inner class
public class Inner_class {
// Static method of Inner class
public static void method1()
{
// Displaying the value of a
// static member of the outer class
Console.WriteLine(Outer_class.str);
}
}
}
// Driver Class
public class GFG {
// Main method
static public void Main()
{
// Accessing static method1
// of the inner class
Outer_class.Inner_class.method1();
}
}
输出:
Geeksforgeeks
- 内部类可以访问外部类中声明的非静态成员，如下例所示: 例:
C
// C# program to illustrate the
// concept of nested class
// accessing non-static member
// of the outer class
using System;
// Outer class
public class Outer_class {
// Non-static data
// member of outer class
public int number = 1000000;
// Inner class
public class Inner_class {
// Static method of Inner class
public static void method1()
{
// Creating the object of the outer class
Outer_class obj = new Outer_class();
// Displaying the value of a
// static member of the outer class
// with the help of obj
Console.WriteLine(obj.number);
}
}
}
// Driver Class
public class GFG {
// Main method
static public void Main()
{
// Accessing static method1
// of inner class
Outer_class.Inner_class.method1();
}
}
输出:
1000000
- 实例内部类可以访问外部类中声明的非静态成员，如下例所示: 例:
C
// C# program to illustrate the
// concept of nested class
// accessing non-static member
// of the outer class
using System;
// Outer class
public class Outer_class {
// Non-static data
// member of outer class
public int number = 2000000;
// Non-static reference to Inner_class
// instance.
public Inner_class Inner { get; set; }
// Constructor to establish link between
// instance of Outer_class to its
// instance of the Inner_class
public Outer_class() {
this.Inner = new Inner_class(this);
}
// Inner class
public class Inner_class {
// private field to hold
// reference to an instance
// of the Outer_class
private Outer_class obj;
// constructor that establishes
// a reference to the Outer_class
// to use within an Inner_cass instance
public Inner_class(Outer_class outer)
{
obj = outer;
}
// Method of Inner class
public void method1()
{
// Displaying the value of a
// member of the outer class
// with the help of obj
Console.WriteLine(obj.number);
}
}
}
// Driver Class
public class GFG {
// Main method
public static void Main()
{
// Create instance of Outer_class
Outer_class Outer = new Outer_class();
// Accessing static method1
// of inner class
Outer.Inner.method1();
}
}
输出:
2000000
- 嵌套类的范围由其封闭类的范围限定。
- 默认情况下，嵌套类是私有的。
- 在 C# 中，允许用户将一个类(包括嵌套类)继承到另一个类中。 例:
C
// C# program to illustrate the
// concept inheritance
using System;
// Outer class
public class Outer_class {
// Method of outer class
public void method1()
{
Console.WriteLine("Outer class method");
}
// Inner class
public class Inner_class {
}
}
// Derived class
public class Exclass : Outer_class {
// Method of derived class
public void func()
{
Console.WriteLine("Method of derived class");
}
}
// Driver Class
public class GFG {
// Main method
static public void Main()
{
// Creating object of
// the derived class
Exclass obj = new Exclass();
obj.func();
obj.method1();
}
}
输出:
Method of derived class
Outer class method
- 在 C# 中，允许用户从外部类继承嵌套类。
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