using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public static void Main()

    {

        Program pg = new Program();

        int ? [] req = new int ? []{2000, 3000};

        var res = pg.GetData(req);

        foreach (var item in res)

        {

            Console.WriteLine(item.itemId);

        }

​

        Console.ReadLine();

    }

​

    public List<ItemViewModel> GetData(int ? [] categoryIds)

    {

        List<int ? > catIds = categoryIds.ToList();

        List<ItemViewModel> model = new List<ItemViewModel>();

              model.Add(new ItemViewModel() { itemId = 0, itemName = "item 1 ", categoryId = 1000 });

            model.Add(new ItemViewModel() { itemId = 2, itemName = "item 1 ", categoryId = 2000 });

            model.Add(new ItemViewModel() { itemId = 3, itemName = "item 1 ", categoryId = 3000 });

            model.Add(new ItemViewModel() { itemId = 4, itemName = "item 1 ", categoryId = 4000 });

        /*var result = (

            from a in model

            join b in catIds on a.itemId equals b

            select a).Distinct();

        return result.ToList(); */

        return  model.Where(i => catIds.Contains(i.categoryId.Value)).ToList();

    }

}

​

public class ItemViewModel

{

    public int itemId

    {

        get;

        set;

    }

​

    public string itemName

    {

        get;

        set;

    }

​

    public int ? categoryId

    {

        get;

        set;

    }

}