GroupBy 项不相等

问：

我正在遍历一个枚举项，并对每个条目执行相等性检查。但是，在单步执行此代码时，我可以看到从未满足相等性检查。IGrouping

namespace EqualityGroupingTest
{
    public class Reading
    {
        public int Id { get; set; }
        public string Label { get; set; }
        public int Measurement { get; set; }
    }

    class Program
    {
        static void Main(string[] args)
        {
            var readings = new List<Reading>()
            {
                new Reading() {Id = 1, Label = "A101", Measurement = 3},
                new Reading() {Id = 2, Label = "A101", Measurement = 5},
                new Reading() {Id = 3, Label = "A101", Measurement = 8},
                new Reading() {Id = 4, Label = "A102", Measurement = 2},
                new Reading() {Id = 5, Label = "A102", Measurement = 5},
                new Reading() {Id = 6, Label = "A102", Measurement = 9}
            };

            var offset = -1;
            var grouping = readings.GroupBy(i => i.Label);
            foreach (var group in grouping)
            {
                var range = (group.Last().Measurement - group.First().Measurement);

                if(group.Equals(grouping.Last()))
                {
                    range += offset;
                }
            }
        }
    }
}

检查我是否正在查看最后一个分组的代码永远不会得到满足。我可以从以下位置更改此代码：

if(group.Equals(grouping.Last()))

自：

if(group.Key.Equals(grouping.Last().Key))

这解决了问题，但我不明白为什么没有满足检查。我可以看到变量和之间的哈希码在监视窗口中是不同的，但同样，我不确定为什么会这样。如果有人能澄清为什么会发生这种情况，我想知道吗？IGroupinggroupgrouping.Last()