.net - LinkedList.Contains。比较对象的方法是什么？

Question

LinkedList.Contains 方法。 (.NET 2)

里面的对象是怎么比较的？ (等于？CompareTo？)

MSDN 什么也没说。

情况:

interface IClass
{
    string GetName();
}

class Class1 : IClass, IEquatable<Class1>
{
    public string FirstName;
    public string LastName;

    string IClass.GetName() { return FirstName; }

    bool IEquatable<Class1>.Equals(Class1 other)
    {
        return FirstName.Equals(other.FirstName);
    }
}

class Class2 : IClass, IEquatable<Class2>
{
    public string FirstName;
    public string LastName;

    string IClass.GetName() { return LastName; }

    bool IEquatable<Class2>.Equals(Class2 other)
    {
        return LastName.Equals(other.LastName);
    }
}

public void TestMethod() 
{
    Class1 c1 = new Class1();
    c1.FirstName = "fn";
    c1.FirstName = "ln";

    Class2 c2 = new Class2();
    c2.FirstName = "fn";
    c2.FirstName = "ln";

    Class1 c3 = new Class1();
    c3.FirstName = "fn";
    c3.FirstName = "ln";

    LinkedList<IClass> myList = new LinkedList<IClass>();
    myList.AddFirst(c1);
    myList.AddFirst(c2);
    // false here
    MessageBox.Show("myList<IClass> contains c3? - " + (myList.Contains(c3)));

    LinkedList<Class1> myList1 = new LinkedList<Class1>();
    myList1.AddFirst(c1);
    myList1.AddFirst(c1);
    // true here
    MessageBox.Show("myList1<Class1> contains c3? - " + (myList1.Contains(c3)));
}

Answer 1

因为链表不是字典，所以我期望它使用EqualityComparer<T>.Default.Equals(x,y) .

这支持(按顺序):

• IEquatable<T> (对于有问题的 T)
• object.Equals (默认使用引用相等性，或支持覆盖 Equals(object) )

请注意 EqualityComparer<T>还处理通常的 null两个类和Nullable<T>的规则等.

(更新:已检查并更正；来自 Find(T))

...
EqualityComparer<T> comparer = EqualityComparer<T>.Default;
...
if (comparer.Equals(head.item, value)) {...}
...

---

更新以证明此功能在 ISomeInterface: IEquatable<ISomeInterface> 时有效，根据评论:

using System;
using System.Collections.Generic;


class Program
{
    static void Main()
    {
        LinkedList<IFoo> foos = new LinkedList<IFoo>();
        foos.AddLast(new Foo1("abc"));
        foos.AddLast(new Foo2("def"));
        Console.WriteLine("checking contains...");
        bool c = foos.Contains(new Foo1("ghi"));
        Console.WriteLine("...done");
    }
}
interface IFoo : IEquatable<IFoo>
{
    void Bar();
}
class Foo1 : IFoo
{
    public string Value { get; set; }
    public Foo1(string value) { Value = value; }
    public override bool Equals(object other)
    {
        Console.WriteLine(Value + " > override Equals");
        return base.Equals(other);
    }
    bool IEquatable<IFoo>.Equals(IFoo other)
    {
        Console.WriteLine(Value + " > explicit Equals");
        return base.Equals(other);
    }
    public void Bar() { }
    public override int GetHashCode() { return base.GetHashCode(); }
}
class Foo2 : IFoo
{
    public string Value { get; set; }
    public Foo2(string value) { Value = value; }
    public override bool Equals(object other)
    {
        Console.WriteLine(Value + " > override Equals");
        return base.Equals(other);
    }
    public bool Equals(IFoo other)
    {
        Console.WriteLine(Value + " > implicit Equals");
        return base.Equals(other);
    }
    public void Bar() { }
    public override int GetHashCode() { return base.GetHashCode(); }
}