如何在没有任何数字作为字段的情况下覆盖 GetHashCode()？

Question

显示如何覆盖 Equals(object) 和 GetHashCode() 的所有资源都使用数字字段来实现 GetHashCode() 方法：

Implementing the Equals Method
What's the best strategy for Equals and GetHashCode?
Why is it important to override GetHashCode when Equals method is overridden?

但是，在我的 class 中，我没有任何数字字段。它是树中的一个节点，引用其父节点、子节点和接口作为数据：

public class Node
{
    private IInterface myInterface;
    private Node parent;
    private List<Node> children = new List<Node>();

    public override bool Equals(object obj)
    {
        if (obj == null || GetType() != obj.GetType())
        {
            return false;
        }
        var node = (Node)obj;
        return myInterface == node.myInterface;
    }

    public override int GetHashCode()
    {
        ???
    }
}

我应该用什么设置哈希码？

Answer 1

根据 Equals 实现，当且仅当它们的 myInterface 相等时，两个 Nodes 实例才相等：

public override bool Equals(object obj)
{
    if (obj == null || GetType() != obj.GetType())
    {
        return false;
    }
    var node = (Node)obj;

    // instances are equal if and only if myInterface's are equal
    return myInterface == node.myInterface;
}

这就是为什么 myInterface 是 GetHashCode 的唯一来源：

 public override int GetHashCode()
 {
    return null == myInterface ? 0 : myInterface.GetHashCode();
 }

P.S.（已编辑，感谢 Kris Vandermotten）通常，检查 ReferenceEquals 在 Equals 实现之前比较可能 time/resource 消耗 myInterfaces:

 public override bool Equals(object obj) {
   // Easy tests: 
   // 1. If "this" and "obj" are in fact just the same reference?
   // 2. Since `Node` (or Equals) is not sealed, the safiest is to check types 
   if (object.ReferenceEquals(this, obj))
     return true;
   else if (null == obj || other.GetType() != GetType()) 
     return false;

   // Potentially time/resource cosuming (we don't know IInterface implementation)
   return ((Node) obj).myInterface == myInterface;
 }

如何在没有任何数字作为字段的情况下覆盖 GetHashCode()？

How do I override GetHashCode() without any numbers as fields?

c#

equality

hashcode

iequalitycomparer

gethashcode