在C＃中创建对象的不同方法

完全面向对象的语言意味着所有内容都表示为一个对象，但是无法区分原始类型和类的对象，但是C＃并不是纯粹面向对象的，因为它支持许多过程编程概念，例如某种程度上的指针。对象是面向对象编程的基本单元，代表现实生活中的实体。一个典型的C＃程序会创建许多对象，如您所知，这些对象通过调用方法进行交互。我们可以通过以下方式在C＃中创建对象：

1)使用’new’运算符：类是一种引用类型，并且在运行时，除非使用new运算符声明了该引用类型的任何对象，否则将为该对象分配一个空值。 new运算符仅在运行时才将内存中的空间分配给对象，这意味着分配是动态的。

句法：

// The className() is a call
// to the constructor
className ObjectName = new className();   

注意：构造函数可以是默认构造函数，也可以是用户定义的构造函数。

例子：

// C# Program to show the use
// of the new Operator
using System;
  
namespace NewOperator {
  
class Rectangle {
  
    public int length, breadth;
  
    // Parameterized Constructor
    // User defined
    public Rectangle(int l, int b)
    {
        length = l;
        breadth = b;
    }
  
    // Method to Calculate Area
    // of the rectangle
    public int Area()
    {
        return length * breadth;
    }
}
  
// Driver Class
class Program {
  
    // Main Method
    static void Main(string[] args)
    {
        // Creating an object using 'new'
        // Calling the parameterized constructor
        // With parameters 10 and 12
        Rectangle rect1 = new Rectangle(10, 12);
  
        // To display are of the Rectangle
        int area = rect1.Area();
        Console.WriteLine("The area of the"+
                   " Rectangle is " + area);
    }
}
}

输出：

The area of the Rectangle is 120

2)创建对现有对象的引用：只能使用类名和引用名声明引用。引用不能独立存在。必须将其分配给相同类的现有对象。引用中所做的任何更改都将保存到引用的对象中。这有点像别名。

句法：

className RefName;
RefName = objectName;

例子：

// C# Program to show the use
// of references
using System;
  
namespace Reference {
  
class Triangle {
  
    public int side, altitude;
    // Not defining a constructor
  
    // Method to calculate area
    // of the Triangle
    public double Area()
    {
        return (double)0.5 * side * altitude;
    }
}
  
// Driver Class
class Program {
  
    // Main Method
    static void Main(string[] args)
    {
        // Creating an object using new
        // calls the default constructor
        Triangle tri1 = new Triangle();
  
        // Only creates a reference of
        // type Triangle
        Triangle tri2;
  
        // Displaying area of tri1
        Console.WriteLine("Area of tri1 is " 
                             + tri1.Area());
  
        // Assigns the reference to tri1
        tri2 = tri1;
  
        // Making changes in tri2
        tri2.side = 5;
        tri2.altitude = 7;
  
        // Displaying area of tri1
        // Changes made in the reference tri2
        // are reflected in tri1 also
        Console.WriteLine("Area of tri1 is " 
                             + tri1.Area());
    }
}
}

输出：

Area of tri1 is 0
Area of tri1 is 17.5

3)创建对象数组：如果需要多个相同类的对象，则可以创建对象数组。这将要求您首先声明数组，然后初始化每个元素{在这种情况下为object}。您可以使用for循环进行初始化。

句法：

className[] arrayName = new className[size];

// C# Program to illustrate how to 
// create the array of objects
using System;
  
namespace ArrayofObjects {
  
class Circle {
  
    public int radius;
  
    // Definig Constructor
    public Circle()
    {
        radius = 0;
    }
  
    // Method to set value of radius
    public void setValue(int r)
    {
        radius = r;
    }
  
    // Method to calculate the 
    // area of the Circle
    public double Area()
    {
        return (double)3.14 * radius * radius;
    }
}
  
// Driver Class
class Program {
  
    // Main Method
    static void Main(string[] args)
    {
        // To declare an array of two objects
        Circle[] circleArray = new Circle[2];
  
        // Initialize the objects
        circleArray[0] = new Circle();
        circleArray[1] = new Circle();
  
        // to set values for the radius
        circleArray[0].setValue(1);
        circleArray[1].setValue(2);
  
        // for loop to display areas
        for (int i = 0; i < circleArray.Length; i++) 
        {
            Console.Write("Area of circle with radius " + (i + 1));
            Console.Write(" is " + circleArray[i].Area() + "\n");
        }
    }
}
}

输出：

Area of circle with radius 1 is 3.14
Area of circle with radius 2 is 12.56