C# nested array of int type flattener

FlattenArrayExample.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Web.Script.Serialization;

namespace FlattenArrayExample
{
    public static class Program
    {
	public static void Main()
	{

		var originalData = "[[1,2,[3]],4]";
		//var originalData = "[[],[1,2,[3]],4]";
		//var originalData = "[0,[1,2,[3]],4,[[1]],[],6,[8,9],7]";
		//var originalData = "[ 1, 2, 3, \"text\" ]";

		var deserializedData = new JavaScriptSerializer().DeserializeObject(originalData);

		var flattenedArray = ArrayUtils.getFlattenedIntArray(deserializedData);

		if (flattenedArray != null)
		{
			var flattenedArraySerialized = new StringBuilder();
			foreach (var el in flattenedArray)
			{
				flattenedArraySerialized.Append($"{el},");
			}
			Console.WriteLine($"{originalData} -> [{flattenedArraySerialized}]");
		}
		Console.ReadLine();
	}

   }

   public static class ArrayUtils
   {

	public static int[] getFlattenedIntArray(object nestedArray)
	{

		var flattenedArray = new List<int>();

		var nestedArrayType = nestedArray.GetType();
		var expectedType = typeof(int);

		if (nestedArrayType.IsArray) 
		{
			foreach (var el in nestedArray as object[]) 
			{
				foreach (var retIntEl in getFlattenedIntArray(el)) {
					flattenedArray.Add(retIntEl);
				}
			}
		} 
		else if (nestedArrayType == expectedType) 
		{
			flattenedArray.Add((int)nestedArray);
		} 
		else 
		{
			return new int[0];
		}

		return flattenedArray.ToArray();
	}

    }
}