Question

How do you sort a List alphanumerically by the value in string[0]?

Answer 1

Try

list.Sort((s, t) => String.Compare(s[0], t[0]));

This will sort lexicographically by the first element of each array in list.

Since I don’t know exactly what you mean by “alphanumerically”, if you need a custom string comparing routing, you should do this:

class MyStringComparer : IComparer<string> {
    public int Compare(string s, string t) {
        // details elided
    }
}

and then

var comparer = new MyStringComparer();
list.Sort((s, t) => comparer.Compare(s[0], t[0]));