在IEqualityComparer中包装委托

在 IEqualityComparer 中包装委托是一种在比较对象时应用自定义规则的方法。委托可以传递到 IEqualityComparer 的 Compare 方法中，以便定义对象之间要进行比较的规则。下面是一个使用 IEqualityComparer 包装委托的基本示例：

#region IEqualityComparer 使用示例
public static class ComparerHelper
{
    public static IEqualityComparer<T> Create<T>(Func<T, T, int> compare) => new CustomEqualityComparer<T>(compare);

    private class CustomEqualityComparer<T> : IEqualityComparer<T>
    {
        private readonly Func<T, T, int> _compare;

        public CustomEqualityComparer(Func<T, T, int> compare) => _compare = compare;

        public bool Equals(T x, T y) => _compare(x, y) == 0;

        public int GetHashCode(T obj) => obj.GetHashCode();
    }
}

class Program
{
    static void Main(string[] args)
    {
        int[] arr1 = { 1, 2, 3, 4 };
        int[] arr2 = { 10, 20, 30, 40 };

        Console.WriteLine("Without custom equality comparer:");
        Array.Sort(arr1, Array.Equals<int>(arr1, arr2, (a, b) => a.CompareTo(b)));
        Array.Sort(arr2, Array.Equals<int>(arr1, arr2, (a, b) => a.CompareTo(b)));

        Console.WriteLine("With custom equality comparer:");
        Array.Sort(arr1, new ComparerHelper.CustomEqualityComparer<(int x, int y)>((a, b) => a.Value.CompareTo(b)));
        Array.Sort(arr2, new ComparerHelper.CustomEqualityComparer<(int x, int y)>((a, b) => a.Value.CompareTo(b)));

        for (int i = 0; i < arr1.Length; i++)
        {
            for (int j = 0; j < arr2.Length; j++)
            {
                if(!arr1.Equals(arr2, new ComparerHelper.CustomEqualityComparer<(int x, int y)>((a, b) => a.Value.CompareTo(b)))))
                Console.WriteLine(i + "," + j + ": The elements are not equal!");
            }
        }

        Console.ReadLine();

    }
}
#endregion

在这个示例中，我们定义了一个create函数，它接受一个委托，并返回一个新的 CustomEqualityComparer<T> 实例。这里使用了 lambda 表达式 a => a.Value.CompareTo(b) 作为自定义比较规则。