自定义HTTP处理程序显示图片（asp.net 2.0）

自定义HTTP处理程序，就是HTTP处理程序必须实现接口System.Web.IHttpHandler。
在实现接口IHttpHandler时，必须做两件事，一件事是设置IsReusable属性，另一件事是实现ProcessRequest()方法。
创建Generic Handler.

<%@ 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) {
// Set up the response settings
context.Response.ContentType = "image/jpeg";
context.Response.Cache.SetCacheability(HttpCacheability.Public);
context.Response.BufferOutput = false;
// Setup the Size Parameter
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;
}
// Setup the PhotoID Parameter
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);
}
// Get the photo from the database, if nothing is returned, get the default "placeholder" photo
if (stream == null) stream = PhotoManager.GetPhoto(size);
// Write image stream to the response stream
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);
}
}

}

public static Stream GetPhoto(int photoid, PhotoSize size) {
using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["Personal"].ConnectionString)) {
using (SqlCommand command = new SqlCommand("GetPhoto", connection)) {
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add(new SqlParameter("@PhotoID", photoid));
command.Parameters.Add(new SqlParameter("@Size", (int)size));
bool filter = !(HttpContext.Current.User.IsInRole("Friends") || HttpContext.Current.User.IsInRole("Administrators"));
command.Parameters.Add(new SqlParameter("@IsPublic", filter));
connection.Open();
object result = command.ExecuteScalar();
try {
return new MemoryStream((byte[])result);
} catch {
return null;
}
}
}
}

public static Stream GetFirstPhoto(int albumid, PhotoSize size) {
using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["Personal"].ConnectionString)) {
using (SqlCommand command = new SqlCommand("GetFirstPhoto", connection)) {
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add(new SqlParameter("@AlbumID", albumid));
command.Parameters.Add(new SqlParameter("@Size", (int)size));
bool filter = !(HttpContext.Current.User.IsInRole("Friends") || HttpContext.Current.User.IsInRole("Administrators"));
command.Parameters.Add(new SqlParameter("@IsPublic", filter));
connection.Open();
object result = command.ExecuteScalar();
try {
return new MemoryStream((byte[])result);
} catch {
return null;
}
}
}
}