featurecache.cs

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using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Caching;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;

using AspNet.StarterKits.Classifieds.BusinessLogicLayer;

namespace AspNet.StarterKits.Classifieds.Web
{
	public class CachedFeaturedAd
	{
		private int _adId;
		private int _previewImageId;
		private string _title;

		public int AdId { get { return _adId; } }
		public int PreviewImageId { get { return _previewImageId; } }
		public string Title { get { return _title; } }

		public CachedFeaturedAd(int adId, int previewImageId, string title)
		{
			this._adId = adId;
			this._previewImageId = previewImageId;
			this._title = title;
		}
	}

	public sealed class FeaturedAdCache
	{
		private const int NumCachedFeatures = 10;
		private const int CacheLifeTime = 1; // in minutes

		private static Random random = new Random();
		private const string CacheKeyPrefix = "FeaturedAdCache_";

		private FeaturedAdCache()
		{
		}

		public static void ClearAll(HttpContext context)
		{
			for (int i = 0; i < NumCachedFeatures; i++)
				context.Cache.Remove(GetCacheKey(i));
		}

		private static string GetCacheKey(int featureCacheNumber)
		{
			return CacheKeyPrefix + featureCacheNumber.ToString();
		}

		public static CachedFeaturedAd GetFeaturedAd()
		{
			return GetFeaturedAd(HttpContext.Current);
		}


		public static CachedFeaturedAd GetFeaturedAd(HttpContext context)
		{
			if (context == null)
				return null;

			int featureCacheNumber = random.Next(0, NumCachedFeatures - 1);
			string cacheKey = GetCacheKey(featureCacheNumber);

			CachedFeaturedAd feature = context.Cache[cacheKey] as CachedFeaturedAd;
			if (feature == null)
			{
				feature = FetchFeaturedAd();
				if (feature != null)
				{
					DateTime expiration = DateTime.Now.AddMinutes(CacheLifeTime);
					context.Cache.Add(cacheKey, feature, null, expiration, TimeSpan.Zero, System.Web.Caching.CacheItemPriority.Normal, null);
				}
			}

			return feature;

		}

		private static CachedFeaturedAd FetchFeaturedAd()
		{
			CachedFeaturedAd feature = null;

			AdsDataComponent.AdsDataTable table = AdsDB.GetFeaturedAdsSelection(1);
			if (table != null && table.Rows.Count > 0)
			{
				AdsDataComponent.AdsRow featuredAd = table.Rows[0] as AdsDataComponent.AdsRow;
				feature = new CachedFeaturedAd(featuredAd.Id, featuredAd.PreviewImageId, featuredAd.Title);
			}

			return feature;
		}
	}
}