using System;

using System.Web;

using System.Collections.Specialized;

using System.Linq;

public class Program

{

    public static string[] QueryStringOmissions = new string[] { "b" };

​

    public static NameValueCollection SortAndRemove(NameValueCollection collection)

    {

        var orderedKeys = collection.Cast<string>().Where(k => k != null).OrderBy(k => k);

        var newCollection = HttpUtility.ParseQueryString(String.Empty);

        foreach(var key in orderedKeys)

        {

            if (!QueryStringOmissions.Contains(key))

            {

                foreach(var val in collection.GetValues(key).Select(x => x).OrderBy(x => x).ToArray())

                {

                    newCollection.Add(key, val);

                }

            }

        }

        return newCollection;

    }        

​

    public static Uri SortRemoveQueryStrings(Uri uriResult)

    {

        var qs = HttpUtility.ParseQueryString(uriResult.Query);

        uriResult = new UriBuilder(uriResult) { Query = SortAndRemove(qs).ToString() }.Uri;

        return uriResult;

    }

    public static void Main()

    {

        var a = new Uri("http://example.com?a=1&d=5&c=3&b=2&a=4");

        var b = new Uri("http://example.com?d=5&a=4&c=3&b=2&a=1");

        var aFixed = SortRemoveQueryStrings(a);

        var bFixed = SortRemoveQueryStrings(b);

        Console.WriteLine(aFixed);

        Console.WriteLine(bFixed);

        Console.WriteLine(aFixed.Equals(bFixed));

    }

}