Test whether AsEnumerable differs from casting regarding a hidden extension method.

AsEnumerableVsCasting.cs

using System;
using System.Collections.Generic;
using System.Linq;

namespace AsEnumerableVsCasting
{
    class AsEnumerableVsCasting
    {
        static void Main(string[] args)
        {
            var sneaky = new Sneaky { "a", "b", "c" };

            Print(sneaky.Select(s => s)); // prints x, y, z (specialized method; Enumerable.Select is hidden)
            Print(sneaky.AsEnumerable().Select(s => s)); // prints a, b, c (generic method Enumerable.Select)
            Print(((IEnumerable<string>) sneaky).Select(s => s)); // prints a, b, c (generic method Enumerable.Select)
        }

        static void Print(IEnumerable<string> list)
        {
            Console.WriteLine(string.Join(", ", list));
        }
    }

    class Sneaky : List<string>
    {
        public IEnumerable<TResult> Select<TResult>(Func<string,TResult> project)
        {
            return (new List<string> { "x", "y", "z" }).Select(project);
        }
    }
}

Turns out, AsEnumerable and casting to IEnumerable<T> work the same way, here.