在 C# 中创建对象的不同方式
完全面向对象的语言意味着一切都被表示为对象，但是不能区分基元类型和类的对象，但是 C# 不是纯粹面向对象的，因为它在一定程度上支持许多过程性编程概念，比如指针。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# 程序创建许多对象，正如你所知道的，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:类是引用类型，在运行时，引用类型的任何对象都被赋予空值，除非它是使用新运算符声明的。新运算符仅在运行时将内存中的空间分配给对象，这意味着分配是动态的。 语法:
// 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，也可以是自定义构造函数。 例:
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// 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);
}
}
}
Output:
The area of the Rectangle is 120
2)创建对现有对象的引用:引用只能用类名和引用名声明。引用不能独立存在。它必须被分配给同一个类的一个已经存在的对象。引用中所做的任何更改都将保存到它所引用的对象中。有点像化名。 语法:
className RefName;
RefName = objectName;
例:
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// 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());
}
}
}
Output:
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别的对象，可以创建一个对象数组。这将要求您首先声明数组，然后初始化每个元素{在这种情况下是对象}。您可以使用 for 循环进行初始化。 语法:
className[] arrayName = new className[size];
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// C# Program to illustrate how to
// create the array of objects
using System;
namespace ArrayofObjects {
class Circle {
public int radius;
// Defining 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");
}
}
}
}
Output:
Area of circle with radius 1 is 3.14
Area of circle with radius 2 is 12.56
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