专业LINQ手册中的orderby签名错误?

根据 Pro LINQ: Language Integrated Query in C# 2008 原型 排序 运算符是

public static IOrderedEnumerable<T> OrderBy<T, K>(
    this IEnumerable<T> source,
    Func<T, K> keySelector)
where
    K : IComparable<K>

但是 MSDN documentation 在上没有泛型约束 TKEY 应该是那种 IComparable<TKey>

public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(
    this IEnumerable<TSource> source,
    Func<TSource, TKey> keySelector
)

我基本上是按 单位 然后通过 尺寸 .

    var sortedInventories = inventories
                            .OrderBy(inventory => inventory.Unit)
                            .OrderBy(inventory => inventory.Size);

从上面的代码片段中,lambda表达式只返回要排序的库存属性。它看起来不像返回 IComparer<T>

但是根据逻辑,lambda表达式的类型应该是 i比较程序<t> .

哪一个是正确的声明 OrderBy ?
ApRES.com Errata page 没有相关信息)

这是我创建用来测试的示例应用程序 排序

public class Program
{
    public static void Main(string[] args)
    {
        var inventories = new[] {
            new Inventory { Unit = 1, Size = 2 },
            new Inventory { Unit = 2, Size = 4 },
            new Inventory { Unit = 3, Size = 6 },
        };
        var sortedInventories = inventories
                                .OrderBy(inventory => inventory.Unit)
                                .OrderBy(inventory => inventory.Size);

        foreach (var inventory in sortedInventories)
            Console.WriteLine("Unit: {0}; Size = {1}", inventory.Unit, inventory.Size);
    }
}

public class Inventory
{
    public int Unit { get; set; }
    public double Size { get; set; }
}