https://zhidao.baidu.com/question/681553612286124812.html
如果有类A和类B都继承了类C，类A已经存入到集合中了，那么此时用该方法判断类B，是会返回true还是false?
你的类和List如何定义的？
我测试是返回false，定义如下：
public class C { }
public class A:C { }
public class B:C { }
private void button1_Click(object sender,EventArgs e)
{
A a=new A();
B b=new B();
C c=new C();
List
lst.Add(a);
if(lst.Contains(b))
MessageBox.Show("true!");
else
MessageBox.Show("false!");
}
结果：
false!
list的Contains方法是根据其元素类型定义的Equals方法来判断是否重复的。因为是实例方法，所以与继承几乎没关系。看示例：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 | class Program { static void Main(string[] args) { List<A> As = new List<A>() { new A(1,2) }; A a1 = new A(1, 22); Console.WriteLine(As.Contains(a1));//false A a2 = new A(11, 2); Console.WriteLine(As.Contains(a2));//false //你自己对比上下区别 List<B> Bs = new List<B>() { new B(1,2) }; B b1 = new B(1, 22); Console.WriteLine(Bs.Contains(b1));//true B b2 = new B(11, 2); Console.WriteLine(Bs.Contains(b2));//true Console.ReadLine(); } } class A { public int a; public int b; public A(int a, int b) { this.a = a; this.b = b; } public override bool Equals(object obj) { if (obj == null) return false; if (obj.GetType() != typeof(A)) return false; A c = obj as A; return (this.a == c.a && this.b == c.b); } } class B { public int a; public int b; public B(int a, int b) { this.a = a; this.b = b; } public override bool Equals(object obj) { if (obj == null) return false; if (obj.GetType() != typeof(B)) return false; B c = obj as B; return (this.a == c.a || this.b == c.b); } } |
