cache.cs

Sharp Map 用于制作GIS系统S harp Map 用于制作GIS系统S harp Map 用于制作GIS系统

// Copyright 2005, 2006 - Morten Nielsen (www.iter.dk)
//
// This file is part of SharpMap.
// SharpMap is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
// 
// SharpMap is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public License
// along with SharpMap; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 

using System;
using System.Collections.Generic;
using System.Text;

namespace SharpMap.Web
{
	/// <summary>
	/// Class for storing rendered images in the httpcache
	/// </summary>
	public class Caching
	{
		/// <summary>
		/// Inserts an image into the HttpCache and returns the cache identifier.
		/// </summary>
		/// <remarks>
		/// Image can after insertion into the cache be requested by calling getmap.aspx?ID=[identifier]<br/>
		/// This requires you to add the following to web.config:
		/// <code escaped="true">
		/// <httpHandlers>
		///	   <add verb="*" path="GetMap.aspx" type="SharpMap.Web.HttpHandler,SharpMap"/>
		/// </httpHandlers>
		/// </code>
		/// <example>
		/// Inserting the map into the cache and setting the ImageUrl:
		/// <code>
		/// string imgID = SharpMap.Web.Caching.CacheMap(5, myMap.GetMap(), Session.SessionID, Context);
		/// imgMap.ImageUrl = "getmap.aspx?ID=" + HttpUtility.UrlEncode(imgID);
		/// </code>
		/// </example>
		/// </remarks>
		/// <param name="minutes">Number of minutes to cache the map</param>
		/// <param name="map">Map reference</param>
		/// <returns>Image identifier</returns>
		public static string InsertIntoCache(int minutes, System.Drawing.Image map)
		{
			string guid = System.Guid.NewGuid().ToString().Replace("-","");
			System.IO.MemoryStream MS = new System.IO.MemoryStream();
			map.Save(MS, System.Drawing.Imaging.ImageFormat.Png);
			byte[] buffer = MS.ToArray();
			System.Web.HttpContext.Current.Cache.Insert(guid, buffer, null, System.Web.Caching.Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(minutes));
			map.Dispose();
			return guid;
		}
	}
}