using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        string s1 = "bb";

        string s2 = "aa";

        var objS = new NullableRangePair<string>(s1, s2);

        Console.WriteLine("0." + objS);

​

        int? v1 = null;

        int? v2 = 5;

        var objN = new NullableRangePair<int?>(v1, v2);

        Console.WriteLine("9." + objN);

    }

}

​

    public class NullableRangePair<T> 

    {

        public T First { get; private set; }

        public T Second { get; private set; }

        public NullableRangePair(T first, T second)

        {

            //判斷T是不是nullable型別

            Type t1 = typeof(T);

            //if (t1.GetGenericTypeDefinition() != typeof(Nullable<>))

            if (default(T) != null)

            {

                throw new Exception("傳入的型別必需是 Nullable 型別");

            }

​

​

            if (first == null || second == null)

            {

                //如果二個值中有一個沒值,就不必考慮對調大小的事

                this.First = first;

                this.Second = second;

​

                return;

            }

​

​

            Type t2 = Nullable.GetUnderlyingType(t1);

            if (t2 == null) // Michael

                t2 = t1;

            //判斷傳入 t2 型別有沒有實作IComparable<t2>

            var query = t2.GetInterfaces().Where(i => i.IsGenericType

                                                && i.GetGenericTypeDefinition() == typeof(IComparable<>)

                                                && i.GetGenericArguments().Length == 1

                                                && i.GetGenericArguments()[0] == t2)

                                        .Any();

            if (!query)

            {

                throw new Exception("Nullable<T> 的型別必需實作IComparable<T>");

            }

​

​

​

            //是nullable型別,且有實作IComparable<T2>

            //T value1 = (T)Convert.ChangeType(first, t2);

            //T value2 = (T)Convert.ChangeType(second, t2);

​

            var value1 = first;  // Michael

            var value2 = second;

​

            int result = (value1 as IComparable).CompareTo(value2);

​

            if (result <= 0)

            {

                this.First = value1;

                this.Second = value2;

            }

            else

            {

                this.First = value2;

                this.Second = value1;

            }

        }

        public override string ToString()

        {

            return string.Format("{0} ~ {1}", First, Second);

        }       

    }