什么是里氏替换原则?如何在 C# 中实现?
csharpserver side programmingprogramming更新于 2025/10/17 12:37:17
派生类型必须能够完全替换其基类型。
定义:
我们应该能够将子类视为父类。本质上，这意味着所有派生类都应保留其父类的功能，并且不能替换父类提供的任何功能。
里氏替换之前
public class Ellipse {
public double MajorAxis { get; set; }
public double MinorAxis { get; set; }
public virtual void SetMajorAxis(double majorAxis){
this.MajorAxis = majorAxis;
}
public virtual void SetMinorAxis(double minorAxis){
this.MajorAxis = minorAxis;
}
public virtual double Area() {
return MajorAxis * MinorAxis * Math.PI;
}
}
public class Circle : Ellipse {
public override void SetMajorAxis(double majorAxis) {
base.SetMajorAxis(majorAxis);
this.MinorAxis = majorAxis; //在一个圆中，每个轴都是相同的
}
}
public class Result {
public void Method1() {
Circle circle = new Circle();
circle.SetMajorAxis(5);
circle.SetMinorAxis(4);
var area = circle.Area(); //5*4 = 20，但我们预期 5*5 = 25
}
}
After Liskov Substitution
internal class Program {
private static void Main() {
}
}
public class Ellipse {
public double MajorAxis { get; set; }
public double MinorAxis { get; set; }
public virtual void SetMajorAxis(double majorAxis) {
MajorAxis = majorAxis;
}
public virtual void SetMinorAxis(double minorAxis) {
MajorAxis = minorAxis;
}
public virtual double Area() {
return MajorAxis * MinorAxis * Math.PI;
}
}
public class Circle : Ellipse {
public override void SetMajorAxis(double majorAxis) {
base.SetMajorAxis(majorAxis);
this.MinorAxis = majorAxis; //In a cirle, each axis is identical
}
public override void SetMinorAxis(double minorAxis) {
base.SetMinorAxis(minorAxis);
this.MajorAxis = minorAxis;
}
public override double Area() {
return base.Area();
}
}
public class Circle1 {
public double Radius { get; set; }
public void SetRadius(double radius) {
this.Radius = radius;
}
public double Area() {
return this.Radius * this.Radius * Math.PI;
}
}
