using System;
using System.Linq;
using System.Collections.Generic;
 
public class Test
{
	public static void Main()
	{
		List<string> items= new List<string>();
items.Add("Item3");  
 
var Order = new [] {
    new { Products = "Item1,Item3,Item4" },
	new { Products = "Item3,Item5,Item6" },
	new { Products = "Item2,Item7,Item6" },
	new { Products = "Item1,Item2" },
	new { Products = "Item1" },
};
 
var results = (from o in Order
    .Where(o => items.Any(i => (","+o.Products+",").Contains(","+i+",")))
	select o
);
 
foreach (var i in results)
	Console.WriteLine(i.Products);
	}
}

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