Flattens an arbitrarily nested array

FlattenArray.cs

using System;
using System.Collections;
using System.Collections.Generic;
	
public class Program
{
    public static void Main()
    {		
        //nested array source
        var source = new object[]{new object[]{1, 2, new[]{3}}, 4};
	
        //flattened
        var flat = source.Flatten<int>();
	
        //display result
        Console.WriteLine(string.Join(", ", flat));
    }
}


public static class ArrayExtension
{
    // flattens the source nested IEnumerable
    // returns an IEnumerable of type T
    // throws an exception if the source and sub-arrays contain anything but T objects
    public static IEnumerable<T> Flatten<T>(this IEnumerable source)
    {
        foreach(var obj in source)
        {
            var childCollection = obj as IEnumerable;
            if(childCollection != null)
            {
                foreach(var child in childCollection.Flatten<T>())
                {
                    yield return (T)child;
                }
            }
            else
            {
                yield return (T)obj;
            }
        }
    }
}