简述：
抽象方法不提供实现，而是强制派生类重写该方法。它在抽象类下声明。抽象方法只有方法定义
虚拟方法具有一个实现，与Abstract方法不同，它可以存在于abstract和non-abstract类中。它为派生类提供了覆盖它的选项。
虚函数
virtual关键字在修改方法，属性，索引器或事件时很有用。当您在类中定义了要在继承的类中实现的函数时，可以使用虚函数。虚拟函数可以在不同的继承类中以不同方式实现，并且对这些函数的调用将在运行时确定。.
以下是一个虚函数-
publcic virtual int area() { }这是显示如何使用虚函数的示例-
示例
using System;namespace PolymorphismApplication {class Shape {protected int width, height;public Shape( int a = 0, int b = 0) {width = a;height = b;}public virtual int area() {Console.WriteLine("家长课区：");return 0;}}class Rectangle: Shape {public Rectangle( int a = 0, int b = 0): base(a, b) {}public override int area () {Console.WriteLine("Rectangle class area ");return (width * height);}}class Triangle: Shape {public Triangle(int a = 0, int b = 0): base(a, b) {}public override int area() {Console.WriteLine("三角形类区域：");return (width * height / 2);}}class Caller {public void CallArea(Shape sh) {int a;a = sh.area();Console.WriteLine("Area: {0}", a);}}class Tester {static void Main(string[] args) {Caller c = new Caller();Rectangle r = new Rectangle(10, 7);Triangle t = new Triangle(10, 5);c.CallArea(r);c.CallArea(t);Console.ReadKey();}}}
输出结果
Rectangle class areaArea: 70三角形类区域：Area: 25
抽象函数
C#中的abstract关键字用于抽象类和抽象函数。C#中的抽象类包括抽象和非抽象方法。
以下是C#中抽象类中抽象函数的示例-
示例
using System;public abstract class Vehicle {public abstract void display();}public class Bus : Vehicle {public override void display() {Console.WriteLine("Bus");}}public class Car : Vehicle {public override void display() {Console.WriteLine("Car");}}public class Motorcycle : Vehicle {public override void display() {Console.WriteLine("Motorcycle");}}public class MyClass {public static void Main() {Vehicle v;v = new Bus();v.display();v = new Car();v.display();v = new Motorcycle();v.display();}}
输出结果
BusCarMotorcycle
