Extension methods for converting NameValueCollection to a query string

NameValueCollectionExtensions.cs

using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;

namespace System.Collections.Specialized
{
    public static class NameValueCollectionExtensions
    {
        /// <summary>
        /// Converts a name/value collection to a query string by joining
        /// each name and value pair with equals (=), and then combining
        /// all the pairs into a single query string by joining them
        /// with the ampersand (&) character.
        /// </summary>
        /// <param name="collection">The collection of values for the query string.</param>
        /// <returns></returns>
        public static string ToQueryString(this NameValueCollection collection)
        {
            var results = new Dictionary<string, string>();

            foreach (var key in collection.AllKeys.OrderBy(s => s))
            {
                results[key] = collection[key];
            }

            return string.Join("&", results.Select(pair => pair.Key + "=" + (pair.Value ?? "(null)")));
        }

        /// <summary>
        /// Converts a name/value collection to a query string by joining
        /// each name and value pair with equals (=), and then combining
        /// all the pairs into a single query string by joining them
        /// with the ampersand (&) character.
        /// </summary>
        /// <param name="collection">The collection of values for the query string.</param>
        /// <returns></returns>
        public static string ToQueryString(this IEnumerable<KeyValuePair<string,string>> collection)
        {
            return string.Join("&", // Combines all parameters using the ampersand separator
                collection.OrderBy(pair => int.Parse(pair.Key.Substring("parm".Length))) // Sort all the parameters by name
                .Select(pair => pair.Key + "=" 
                    // null values should be serialized as "(null)" instead of be empty.
                    + (pair.Value ?? "(null)")));
        }
    }
}