LinQ 与自定义比较器不同会留下重复项

我有以下课程：

public class SupplierCategory : IEquatable<SupplierCategory>
{
    public string Name { get; set; }
    public string Parent { get; set; }

    #region IEquatable<SupplierCategory> Members

    public bool Equals(SupplierCategory other)
    {
        return this.Name == other.Name && this.Parent == other.Parent;
    }

    #endregion
}

public class CategoryPathComparer : IEqualityComparer<List<SupplierCategory>>
{
    #region IEqualityComparer<List<SupplierCategory>> Members

    public bool Equals(List<SupplierCategory> x, List<SupplierCategory> y)
    {
        return x.SequenceEqual(y);
    }

    public int GetHashCode(List<SupplierCategory> obj)
    {
        return obj.GetHashCode();
    }

    #endregion
}

我正在使用以下 linq 查询：

CategoryPathComparer comparer = new CategoryPathComparer();
List<List<SupplierCategory>> categoryPaths = (from i in infoList
                                                          select
                                                            new List<SupplierCategory>() { 
                                                             new SupplierCategory() { Name = i[3] },
                                                             new SupplierCategory() { Name = i[4], Parent = i[3] },
                                                             new SupplierCategory() { Name = i[5], Parent = i[4] }}).Distinct(comparer).ToList();

但不同的并没有做我想要它做的事情，如以下代码所示：

comp.Equals(categoryPaths[0], categoryPaths[1]); //returns True

我是否以错误的方式使用它？为什么它们没有按照我的意图进行比较？

编辑： 为了证明比较器确实有效，以下内容应返回 true：

List<SupplierCategory> list1 = new List<SupplierCategory>() {
    new SupplierCategory() { Name = "Cat1" },
    new SupplierCategory() { Name = "Cat2", Parent = "Cat1" },
    new SupplierCategory() { Name = "Cat3", Parent = "Cat2" }
};
List<SupplierCategory> list1 = new List<SupplierCategory>() {
    new SupplierCategory() { Name = "Cat1" },
    new SupplierCategory() { Name = "Cat2", Parent = "Cat1" },
    new SupplierCategory() { Name = "Cat3", Parent = "Cat2" }
};
CategoryPathComparer comp = new CategoryPathComparer();
Console.WriteLine(comp.Equals(list1, list2).ToString());

你的问题是你没有实现IEqualityComparer正确。

当你实施IEqualityComparer<T>, you must实施GetHashCode使得任意两个相等的对象具有相同的哈希码。

否则，您将得到不正确的行为，正如您在这里看到的那样。

您应该按如下方式实现 GetHashCode：（由这个答案)

public int GetHashCode(List<SupplierCategory> obj) {
    int hash = 17;

    foreach(var value in obj)
        hash = hash * 23 + obj.GetHashCode();

    return hash;
}

您还需要覆盖GetHashCode in SupplierCategory保持一致。例如：

public override int GetHashCode() {
    int hash = 17;
    hash = hash * 23 + Name.GetHashCode();
    hash = hash * 23 + Parent.GetHashCode();
    return hash;
}

最后，虽然你不需要，但你可能应该重写Equals in SupplierCategory并让它调用Equals您实施的方法IEquatable.