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:
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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); } }
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