页面范例6 - 异步的照片相簿—重要！！

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.IO;

/// <summary>
/// PictureSupplier 的摘要描述
/// </summary>
public class PictureSupplier
{
public PictureSupplier()
{
...
}

public static DataView GetPictureList()
{
string strPath = "./Images/Europe";

DirectoryInfo myDirInfo;
Array arrFileInfo;
DataTable filesTable = new DataTable();
DataView myDataView;
DataRow myDataRow;

filesTable.Columns.Add("Name", Type.GetType("System.String"));
filesTable.Columns.Add("FullPath", Type.GetType("System.String"));
filesTable.Columns.Add("Length", Type.GetType("System.Int32"));
filesTable.Columns.Add("LastWriteTime", Type.GetType("System.DateTime"));
filesTable.Columns.Add("Extension", Type.GetType("System.String"));

// 取得目录信息。
myDirInfo = new DirectoryInfo(HttpContext.Current.Server.MapPath(strPath));

// 取得文件信息。
arrFileInfo = myDirInfo.GetFiles("*.jpg");

// 循环处理 FileInfo 对象以便将相关文件信息填入数据表对象中。
foreach (FileInfo myFileInfo in arrFileInfo)
{
myDataRow = filesTable.NewRow();
myDataRow["Name"] = myFileInfo.Name;
myDataRow["FullPath"] =
HttpContext.Current.Server.UrlEncode(myFileInfo.FullName);
myDataRow["Length"] = myFileInfo.Length;
myDataRow["LastWriteTime"] = myFileInfo.LastWriteTime;
myDataRow["Extension"] = myFileInfo.Extension;

filesTable.Rows.Add(myDataRow);
}

// 创建一个新的 DataView 对象。
myDataView = filesTable.DefaultView;

// 根据 Name 字段的内容来加以排序。
myDataView.Sort = "Name";

// 将 DataView 对象返回。
return myDataView;
}
}

<asp:ImageButton ID="ImageButton1" runat="server" 
CommandArgument='<%# Eval("Name") %>'
CommandName="ShowLargPhoto" 
ImageUrl= 
'<%# Eval("FullPath", 
"~/DisplaySmallEuropePicture.ashx?PictureFilePath={0}") %>'
ToolTip='<%# Eval("Length", "文档大小{0} 字节") %>' />

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
// 如果用户按下照片缩略图。
if (e.CommandName == "ShowLargPhoto")
{
this.LargeImage.ImageUrl = "~/Images/Europe/" + e.CommandArgument.ToString();
// 调用 LargeImageUpdatePanel 的 Update 方法来更新其内容。
this.LargeImageUpdatePanel.Update();
}
}

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowType == DataControlRowType.DataRow)
{
// 此处不可以用 UpdatePanel.FindControl
ImageButton MyImageButton = (ImageButton)(e.Row.FindControl("ImageButton1"));

  if (MyImageButton != null)
{
MyImageButton.Attributes.Add("onMouseOver", "SetNewBorder(this);");
MyImageButton.Attributes.Add("onMouseOut", "SetOldBorder(this);");
}
}
}

protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
this.LargeImage.ImageUrl = "~/Images/Europe/_DSC0926.JPG";
}
}

<%@ WebHandler Language="C#" Class="DisplaySmallEuropePicture" %>

using System;
using System.Web;
using Microsoft.VisualBasic.Devices;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;

public class DisplaySmallEuropePicture : IHttpHandler 
{    
public void ProcessRequest (HttpContext context) 
{
// 取得传递进来的文件路径。
string PictureFilePath = 
context.Request.QueryString["PictureFilePath"].Trim();

// 改变 HTTP 头的输出格式，以便让浏览器知道所输出的文件格式是 JPEG 格式。
context.Response.ContentType = "Image/JPEG";
context.Response.Clear();
context.Response.BufferOutput = true;
Computer MyComputer = new Computer();
using (MemoryStream ms = new MemoryStream(
MyComputer.FileSystem.ReadAllBytes(PictureFilePath)))
{
using (Bitmap bmp = new Bitmap(ms))
{
// 将照片缩小。
using (Bitmap SmallerBmp = 
new Bitmap(bmp, Convert.ToInt32(bmp.Width * 0.15), 
Convert.ToInt32(bmp.Height * 0.15)))
{
SmallerBmp.Save(context.Response.OutputStream, ImageFormat.Jpeg);
}
}
}
}
...
}