Ashx文件的使用方法

一提到Ashx文件，我们就会想到http handler以及图片加载（在之前我们一般使用ASPX或者Webservice去做），一般做法如下：

Handler.ashx：
<%@ WebHandler Language="C#" class="Handler" %>
using System;
using System.IO;
using System.Web;
public class Handler : IHttpHandler {

public bool IsReusable {
  get {
   return true;
  }
}
public void ProcessRequest (HttpContext context) {
  context.Response.ContentType = "image/jpeg";
  context.Response.Cache.SetCacheability(HttpCacheability.Public);
  context.Response.BufferOutput = false;
  PhotoSize size;
  switch (context.Request.QueryString["Size"]) {
   case "S":
    size = PhotoSize.Small;
    break;
   case "M":
    size = PhotoSize.Medium;
    break;
   case "L":
    size = PhotoSize.Large;
    break;
   default:
    size = PhotoSize.Original;
    break;
  }
  Int32 id = -1;
  Stream stream = null;
  if (context.Request.QueryString["PhotoID"] != null && context.Request.QueryString["PhotoID"] != "") {
   id = Convert.ToInt32(context.Request.QueryString["PhotoID"]);
   stream = PhotoManager.GetPhoto(id, size);
  } else {
   id = Convert.ToInt32(context.Request.QueryString["AlbumID"]);
   stream = PhotoManager.GetFirstPhoto(id, size);
  }
  if (stream == null) stream = PhotoManager.GetPhoto(size);
  const int buffersize = 1024 * 16;
  byte[] buffer = new byte[buffersize];
  int count = stream.Read(buffer, 0, buffersize);
  while (count > 0) {
   context.Response.OutputStream.Write(buffer, 0, count);
   count = stream.Read(buffer, 0, buffersize);
  }
}
}

*.aspx:
<img src="myHttpHander.ashx?id=123" width="20" height="20" />

我们变通以下，发现其实除了可以输出图片以外，还可以输出文字：
Handler.ashx：
<%@ WebHandler Language="C#" class="Handler" %>
using System;
using System.Web;
public class Handler : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";
        context.Response.Write("alert('hi')");
    }

    public bool IsReusable {
        get {
            return false;
        }
    }
}

*.aspx:
弹出alert
<script src="Handler.ashx"></script>
也可以把.ashx当成css文件
<link href="css/Handler.ashx" rel="stylesheet" type="text/css">
xml文件
orderDoc.load("Handler.ashx");

还可以嵌入文字：
Handler.ashx：
<%@ WebHandler Language="C#" class="TestHandler" %>
using System;
using System.Web;
public class TestHandler : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";
        context.Response.Write("document.write(\"Hello World\");");
    }

    public bool IsReusable {
        get {
            return false;
        }
    }
}
*.aspx:
<script type="text/javascript" src="TestHandler.ashx" />

当你希望从ashx或HttpHandler里访问你的Session时,你必须实现IReadOnlySessionState接口.

代码:

using System;
using System.Web;
using System.Web.SessionState;

public class DownloadHandler : IHttpHandler, IReadOnlySessionState
{
   public bool IsReusable { get { return true; } }
  
   public void ProcessRequest(HttpContext ctx)
   {
       ctx.Response.Write(ctx.Session["fred"]);
   }
}