c# - .NET 4 中的比较器<T>.Create

Question

我在 .Net 4.5 中创建了一个比较器:

public static Comparer<Room> RoomComparer = 
  Comparer<Room>.Create((a, b) => a.RoomId.CompareTo(b.RoomId))

如何在 C# .NET 4.0 中创建 Comparer？

Answer 1

您可以使用以下内容

public static class Comparer
{
    public static Comparer<T> Create<T>(Comparison<T> comparison)
    {
        if (comparison == null) throw new ArgumentNullException("comparison");
        return new ComparisonComparer<T>(comparison);
    }
    private sealed class ComparisonComparer<T> : Comparer<T>
    {
        private readonly Comparison<T> comparison;
        public ComparisonComparer(Comparison<T> comparison)
        {
            this.comparison = comparison;
        }
        public override int Compare(T x, T y)
        {
            return comparison(x, y);
        }
    }
}

像这样

public static Comparer<Room> RoomComparer = 
  Comparer.Create<Room>((a, b) => a.RoomId.CompareTo(b.RoomId))