LINQ / Lambda Examples : Aggregate collection

///////////////////////////////////////////////////////////////////////////////
// 
//  Copyright © Schakra Inc. 2009. All rights reserved.
// 
///////////////////////////////////////////////////////////////////////////////

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Web;

namespace Schakra.Samples.DotNet.Linq
{
    /// 

    /// Sample demonstrating aggregating content of a Collection.
    /// 
    public class LinqSample_02
    {
        public void AggregateRequestParameters()
        {
            // Generate Data.
            Random random = new Random();
            List uids = new List();
            for (int i = 0; i < 10; i++)
            {
                uids.Add(random.Next(1, int.MaxValue));
            }

            // Had to use similar code snippet while working with Facebook APIs.
            string uidString = uids.Aggregate(
                string.Empty,
                (s, uid) => string.Format("{0},{1}", s, uid.ToString())
                //  (s, uid) => s + "," + uid.ToString())
            ).Substring(1);

            // Had to use similar code while working with OAuth signature creation.
            SortedList oauthParams = new SortedList();

            // Append all parameters in sorted order.
            string sigBaseString = oauthParams.Aggregate(
                string.Empty,
                (s, kvp) => string.Format(
                    "{0}&{1}={2}", s, UrlEncode(kvp.Key), UrlEncode(kvp.Value))
            ).Substring(1);
        }

        private static Regex hexCharsExp = new Regex("%.{2}", RegexOptions.Compiled);

        // Custom encoding in upper case for OAuth String.
        private static string UrlEncode(string input)
        {
            if (string.IsNullOrEmpty(input))
            {
                return input;
            }

            return hexCharsExp.Replace(
                HttpUtility.UrlEncode(input), m => m.Value.ToUpper());
        }
    }
}