实现的IEqualityComparer< T>在C＃两个属性的对象上 [英] Implementing IEqualityComparer<T> on an object with two properties in C#

问题描述

我有，我需要抢了一堆对不同项目的情况，但我的来源是对象的集合，具有两个属性，就像这样：

I have a case where I need to grab a bunch of items on distinct, but my source is a collection of objects with two properties, like this:

public class SkillRequirement
{
    public string Skill { get; set; }
    public string Requirement { get; set; }
}

我试图让一个集合如下：

I try to get a collection as follows:

SkillRequirementComparer sCom = new SkillRequirementComparer();

var distinct_list = source.Distinct(sCom);

我试图实施的IEqualityComparer< T> 对于这一点，但我摔倒在的GetHashCode（）方法难倒

I tried to implement an IEqualityComparer<T> for this, but I fell stumped at the GetHashCode() method.

有关比较器类：

public class SkillRequirementComparer : IEqualityComparer<SkillRequirement>
{
    public bool Equals(SkillRequirement x, SkillRequirement y)
    {
        if (x.Skill.Equals(y.Skill) && x.Requirement.Equals(y.Requirement))
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    public int GetHashCode(SkillRequirement obj)
    {
        //?????
    }
}

通常我只会用 GetHashCode的（）上的属性，但因为我在比较两个属性，我有点在做什么损失。难道我做错什么，或者失去了一些东西真的很明显？

Normally I would just use GetHashCode() on a property, but because I am comparing on two properties, I'm a bit at a loss of what to do. Am I doing anything wrong, or missing something really obvious?

推荐答案

您可以实施的GetHashCode 以下列方式：

You can implement GetHashCode in the following way:

public int GetHashCode(SkillRequirement obj)
{
    unchecked
    {
        int hash = 17;
        hash = hash * 23 + obj.Skill.GetHashCode();
        hash = hash * 23 + obj.Requirement.GetHashCode();
        return hash;
    }
}

<子>的originally 从J.Skeet

_{originally from J.Skeet}

如果该属性可以是空你应该避免的NullReferenceException ，例如：

If the properties can be null you should avoid a NullReferenceException, e.g.:

int hash = 17;
hash = hash * 23 + (obj.Skill ?? "").GetHashCode();
hash = hash * 23 + (obj.Requirement ?? "").GetHashCode();
return hash;

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