using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public void Main()

{

    List<CustomFormat> l1 = new List<CustomFormat>();

        l1.Add(new CustomFormat("#",1));

        l1.Add(new CustomFormat("##",1));

        l1.Add(new CustomFormat("###",1));

        l1.Add(new CustomFormat("####",1));

​

        List<CustomFormat> l2 = new List<CustomFormat>();

        l2.Add(new CustomFormat("#",1));

        l2.Add(new CustomFormat("##",1));

        l2.Add(new CustomFormat("###",1));

        l2.Add(new CustomFormat("####",1));

        l2.Add(new CustomFormat("## ###.0",1));

​

        var l4 = l1.Union(l2, new CustomFormat()).ToList();

​

        foreach(var l3 in l4)

        {

            Console.WriteLine(l3.Mask + " " + l3.Type);

        }

}

​

public class CustomFormat : IEqualityComparer<CustomFormat>

 {

     private string mask;

​

     public string Mask

     {

         get { return mask; }

         set { mask = value; }

     }

     private int type;//0 for Default 1 for userdefined

​

     public int Type

     {

         get { return type; }

         set { type = value; }

     }

     public CustomFormat(){}

     public CustomFormat(string c_maskin, int c_type)

     {

         mask = c_maskin;

         type = c_type;

     }

​

     public bool Equals(CustomFormat x, CustomFormat y)

     {

        if (ReferenceEquals(x, y)) return true;

​

        //Check whether the products' properties are equal. 

        return x != null && y != null && x.Mask.Equals(y.Mask) && x.Type.Equals(y.Type);

    }

​

     public int GetHashCode(CustomFormat obj)

     {

        //Get hash code for the Name field if it is not null. 

        int hashProductName = obj.Mask == null ? 0 : obj.Mask.GetHashCode();

​

        //Get hash code for the Code field. 

        int hashProductCode = obj.Type.GetHashCode();

​

        //Calculate the hash code for the product. 

        return hashProductName ^ hashProductCode;

    }

 }

}