Sort list <T> inside subclass with LINQ

I know that I can sort a list doing something like this

var result = List<T>.OrderBy(value => value.property);

But I will say that I have something like this

    class Stock
    {
        public Guid ID { get; set; }
        public string Description { get; set; }
    }

    class StockList : List<Stock>
    {
        public enum SomeEnum
        {
            SomeOtherValue = 0,
            SomeOtherOtherValue
        }
        //What if I want method like this using LINQ?
        public void Sort(SomeEnum sortBy)
        {
            switch (sortBy) 
            {
                case SomeValue.SomeOtherOtherValue:
                    //Sort one way
                    break;
                case SomeValue.SomeOtherValue:
                    //Sort another
                    break;
            }
        }
    }

this.OrderBy()(and I suppose other LINQ extensions) return an OrderedCollection and don't seem to affect the original. So, I guess I'm wrong?