Linq distinct不会调用Equals方法

Question

我有以下课程

public class ModInfo : IEquatable<ModInfo>
{
    public int ID { get; set; }
    public string MD5 { get; set; }

    public bool Equals(ModInfo other)
    {
        return other.MD5.Equals(MD5);
    }

    public override int GetHashCode()
    {
        return MD5.GetHashCode();
    }
}

我使用如下方法将一些数据加载到该类的列表中:

public void ReloadEverything() {
    var beforeSort = new List<ModInfo>();
    // Bunch of loading from local sqlite database. 
    // not included since it's reload boring to look at
    var modinfo = beforeSort.OrderBy(m => m.ID).AsEnumerable().Distinct().ToList();
}

问题是Distinct()呼叫似乎没有做到这一点.仍然存在彼此相等的对象.

根据这篇文章:https://msdn.microsoft.com/en-us/library/vstudio/bb348436%28v=vs.100%29.aspx这 是你应该如何做出不同的工作,但它不似乎是在ModInfo对象上调用Equals方法.是什么导致这种情况发生？

示例值:

modinfo[0]: id=2069, MD5 =0AAEBF5D2937BDF78CB65807C0DC047C
modinfo[1]: id=2208, MD5 = 0AAEBF5D2937BDF78CB65807C0DC047C

我不关心选择哪个值,因为md5值相同,它们可能是相同的.

Answer 1

您还需要覆盖Object.Equals,而不仅仅是实现IEquatable.

如果你把它添加到你的班级:

public override bool Equals(object other)
{
    ModInfo mod = other as ModInfo;
    if (mod != null)
        return Equals(mod);
    return false;
}

它应该工作.

有关更多信息,请参阅此文章:正确实现IEquatable

编辑:好的,这是基于GetHashCode的最佳实践的略有不同的实现.

public class ModInfo : IEquatable<ModInfo>
{
    public int ID { get; set; }
    public string MD5 { get; set; }

    public bool Equals(ModInfo other)
    {
        if (other == null) return false;
        return (this.MD5.Equals(other.MD5));
    }

    public override int GetHashCode()
    {
        unchecked
        {
            int hash = 13;
            hash = (hash * 7) + MD5.GetHashCode();
            return hash;
        }
    }

    public override bool Equals(object obj)
    {
        ModInfo other = obj as ModInfo;
        if (other != null)
        {
            return Equals(other);
        }
        else
        {
            return false;
        }
    }
}

你可以验证它:

ModInfo mod1 = new ModInfo {ID = 1, MD5 = "0AAEBF5D2937BDF78CB65807C0DC047C"};
ModInfo mod2 = new ModInfo {ID = 2, MD5 = "0AAEBF5D2937BDF78CB65807C0DC047C"};

// You should get true here
bool areEqual = mod1.Equals(mod2);

List<ModInfo> mods = new List<ModInfo> {mod1, mod2};

// You should get 1 result here
mods = mods.Distinct().ToList();

GetHashCode中的那些具体数字是什么？