using System;

using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

using Microsoft.AspNetCore.Mvc;

using Microsoft.EntityFrameworkCore;

using System.Drawing;

​

public class Program

{

    public static void Main()

    {

        var allowedExtensions = ".png, .jpg, .jped";

        var allowedExtensionList = allowedExtensions.Split(',').ToList();

        //allowedExtensionList.ForEach(x => { Console.WriteLine(x); });

        //allowedExtensionList.ForEach(x => { x = "AAA"; });

        //allowedExtensionList.ForEach(x => { Console.WriteLine(x); });

        for (int i = 0; i < allowedExtensionList.Count - 1; i++)

        {

            allowedExtensionList[i] = allowedExtensionList[i].Trim();

        }

        var ext = System.IO.Path.GetExtension("ahmet.jpg").ToLower();

        Console.WriteLine(ext);

        Console.WriteLine(allowedExtensionList.Contains(ext.Trim()));

​

        if (!allowedExtensionList.Contains(ext.Trim()))

        {

            Console.WriteLine("Hello World");

        }

    }

}