Can I compare elements from 2 lists of T?

Question

I still do not get it to the person who marked my question as duplicate. Does the question linked mean I can't, or I can? If it means I can then how? Do I need to redefine ICompareable? Do I need to customize my own method of comparison to compare elements of 2 List?

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Original question below

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I'm playing with generics in C#. I have 2 lists of type T. Doing a "Less than or Equal to" comparison is apparently a no no. So is there a way I can correctly compare elements between 2 generic lists?

This is for the purpose of learning for fun so no particular task/end goal.

    class aClass<T>
    {
        public void Compare_Generics(T[] m)
        {
            var result = new List<T>();
            var left = new List<T>();
            var right = new List<T>();

            for(int i = 0; i < m.Length; i++)
            {
                if(i < m.Length/2)
                    left.Add(m[i];
                else
                    right.Add(m[i]);
            }

            if(left[0] <= right[0])//This is the no no line that the compiler does not like
            {
                result.Add(left[0]);
            }
        }
    }