using System;

using System.Collections.Generic;

using System.Linq;

public class Drug

{

    public string DIN_NDC { get; set; }

}

​

public class Program

{

    public static void Main()

    {

        List<Drug> drugs = new List<Drug>()

        {

            new Drug() { DIN_NDC = "0" },

            new Drug() { DIN_NDC = "1" },

            new Drug() { DIN_NDC = "2" },

            new Drug() { DIN_NDC = "0" },

        };

        Dictionary<string, Drug> drugsDictionary = drugs.ToDictionary(x => x.DIN_NDC);

    }

}