Generics challenge

gistfile1.cs

namespace HolidayAPI
{
    public class Schedule<T> where T : ISchedulable<IComparable>
    {
        private List<T> values = new List<T>();

        public void AddEvent(in T Event)
        {
            values.Add(Event);
            values = values.OrderBy(r => r).ToList();
        }

        public Schedule<T> ApplyHoliday(Holiday Holiday)
        {
            return this;
        }

        public Schedule()
        {

        }
    }

    public interface ISchedulable<out T> where T : IComparable
    {
        T Value { get; }
    }

    public class DueDate : ISchedulable<Version>
    {
        public Version Value => throw new NotImplementedException();

    }
} 

namespace HolidayAPITests
{
    [TestClass]
    public class ScheduleTests
    {
        [TestMethod]
        public void TestCreate1()
        {
            var schedule = new Schedule<DueDate>();
        }
    }
}

@canton7 - I see, thanks. I had found that solution (I should have mentioned) and wanted to avoid the caller of the constructor having to kmow about the type used to implement DueDate, I want that detail to be an implementation detail. Is there any way?

When we use a ref type it works fine but a value type seems to be fundamentally upsetting it.