ImageHandler.cs :  » Bloggers » BlogEngine.NET » BlogEngine.Core » Web » HttpHandlers » C# / CSharp Open Source

#region Using

using System;
using System.IO;
using System.Web;

#endregion

namespace BlogEngine.Core.Web.HttpHandlers{
  /// <summary>
  /// The ImageHanlder serves all images that is uploaded from
  /// the admin pages. 
  /// </summary>
  /// <remarks>
  /// By using a HttpHandler to serve images, it is very easy
  /// to add the capability to stop bandwidth leeching or
  /// to create a statistics analysis feature upon it.
  /// </remarks>
  public class ImageHandler : IHttpHandler
  {

    #region IHttpHandler Members

    /// <summary>
    /// Gets a value indicating whether another request can use the <see cref="T:System.Web.IHttpHandler"></see> instance.
    /// </summary>
    /// <value></value>
    /// <returns>true if the <see cref="T:System.Web.IHttpHandler"></see> instance is reusable; otherwise, false.</returns>
    public bool IsReusable
    {
      get { return false; }
    }

    /// <summary>
    /// Enables processing of HTTP Web requests by a custom HttpHandler that 
    /// implements the <see cref="T:System.Web.IHttpHandler"></see> interface.
    /// </summary>
    /// <param name="context">An <see cref="T:System.Web.HttpContext"></see> object 
    /// that provides references to the intrinsic server objects 
    /// (for example, Request, Response, Session, and Server) used to service HTTP requests.
    /// </param>
    public void ProcessRequest(HttpContext context)
    {
      if (!string.IsNullOrEmpty(context.Request.QueryString["picture"]))
      {
                string fileName = context.Request.QueryString["picture"];
        OnServing(fileName);
        try
        {
          string folder = BlogSettings.Instance.StorageLocation + "/files/";
          FileInfo fi = new FileInfo(context.Server.MapPath(folder) + fileName);

          if (fi.Exists && fi.Directory.FullName.ToUpperInvariant().Contains(Path.DirectorySeparatorChar + "FILES"))
          {
            context.Response.Cache.SetCacheability(HttpCacheability.Public);
            context.Response.Cache.SetExpires(DateTime.Now.AddYears(1));
            
            if (Utils.SetConditionalGetHeaders(fi.CreationTimeUtc))
              return;

            int index = fileName.LastIndexOf(".") + 1;
            string extension = fileName.Substring(index).ToUpperInvariant();

            // Fix for IE not handling jpg image types
            if (string.Compare(extension, "JPG") == 0)
              context.Response.ContentType = "image/jpeg";
            else
              context.Response.ContentType = "image/" + extension;

            context.Response.TransmitFile(fi.FullName);
            OnServed(fileName);
          }
          else
          {
            OnBadRequest(fileName);
            context.Response.Redirect(Utils.AbsoluteWebRoot + "error404.aspx");
          }
        }
        catch (Exception ex)
        {
          OnBadRequest(ex.Message);
          context.Response.Redirect(Utils.AbsoluteWebRoot + "error404.aspx");
        }
      }
    }

    #endregion

    #region Events

    /// <summary>
    /// Occurs before the requested image is served.
    /// </summary>
    public static event EventHandler<EventArgs> Serving;
    private static void OnServing(string file)
    {
      if (Serving != null)
      {
        Serving(file, EventArgs.Empty);
      }
    }

    /// <summary>
    /// Occurs when a file is served.
    /// </summary>
    public static event EventHandler<EventArgs> Served;
    private static void OnServed(string file)
    {
      if (Served != null)
      {
        Served(file, EventArgs.Empty);
      }
    }

    /// <summary>
    /// Occurs when the requested file does not exist.
    /// </summary>
    public static event EventHandler<EventArgs> BadRequest;
    private static void OnBadRequest(string file)
    {
      if (BadRequest != null)
      {
        BadRequest(file, EventArgs.Empty);
      }
    }

    #endregion

  }
}