filehandler.cs

个人博客系统

#region Using

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

#endregion

namespace BlogEngine.Core.Web.HttpHandlers
{

  /// <summary>
  /// The FileHandler serves all files that is uploaded from
  /// the admin pages except for images. 
  /// </summary>
  /// <remarks>
  /// By using a HttpHandler to serve files, it is very easy
  /// to add the capability to stop bandwidth leeching or
  /// to create a statistics analysis feature upon it.
  /// </remarks>
  public class FileHandler : 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["file"]))
      {
        string fileName = context.Request.QueryString["file"].ToLowerInvariant();
        string folder = BlogSettings.Instance.StorageLocation + "/files/";
        FileInfo info = new FileInfo(context.Server.MapPath(folder) + fileName);

        OnServing(fileName);
        
        if (info.Exists && info.Directory.FullName.ToLowerInvariant().Contains("\\files"))
        {
					context.Response.AppendHeader("Content-Disposition", "inline; filename=" + fileName);
          SetContentType(context, fileName);

          context.Response.TransmitFile(info.FullName);
          OnServed(fileName);
        }
        else
        {
          OnBadRequest(fileName);
          context.Response.Status = "404 Bad Request";
        }
      }
    }

    /// <summary>
    /// Sets the content type depending on the filename's extension.
    /// </summary>
    private static void SetContentType(HttpContext context, string fileName)
    {
      if (fileName.EndsWith(".pdf"))
      {
        context.Response.AddHeader("Content-Type", "application/pdf");
      }
      else 
      {
				context.Response.AddHeader("Content-Type", "application/octet-stream");
      }
    }

    #endregion

    #region Events

    /// <summary>
    /// Occurs when the requested file does not exist;
    /// </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

  }

}