在ASP.NET里轻松实现缩略图

<% @ Page Language="C#" AutoEventWireup="true" CodeFile="Default5.aspx.cs" Inherits="Default5"  %>

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >

< html  xmlns ="http://www.w3.org/1999/xhtml"   >
< head  runat ="server" >
     < title > 无标题页 </ title >
</ head >
< body >
     < form  id ="form1"  runat ="server" enctype="multipart/form-data" >
     < div >
     < asp:Label  id ="Label1"  runat ="server" ></ asp:Label >

     < INPUT  type ="file"  name ="file"  width ="600" >< br >< br >
         < asp:FileUpload  ID ="FileUpload1"  runat ="server" />
       < asp:Button  id ="Button1"  runat ="server"  OnClick ="Button1_Click" ></ asp:Button >

     </ div >
     </ form >
</ body >
</ html >

using  System;
using  System.Data;
using  System.Configuration;
using  System.Collections;
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;
using  System.Drawing.Imaging;


public  partial  class  Default5 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // 在此处放置用户代码以初始化页面
        Label1.Text = "<h3>在ASP.NET里轻松实现缩略图</h3>";
        Button1.Text = "上载并显示缩略图";
    }

    protected void Button1_Click(object sender, System.EventArgs e)
    {
        HttpFileCollection MyFileColl = HttpContext.Current.Request.Files;
        //HttpPostedFile MyPostedFile = MyFileColl[0];
        HttpPostedFile MyPostedFile = FileUpload1.PostedFile;

        if (MyPostedFile.ContentType.ToString().ToLower().IndexOf("image") < 0)
        {
            Response.Write("无效的图形格式。");
            return;
        }
        GetThumbNail(MyPostedFile.FileName, 100, 100,
            MyPostedFile.ContentType.ToString(), false, MyPostedFile.InputStream);
    }
    private System.Drawing.Imaging.ImageFormat GetImageType(object strContentType)
    {
        if ((strContentType.ToString().ToLower()) == "image/pjpeg")
        {
            return System.Drawing.Imaging.ImageFormat.Jpeg;
        }
        else if ((strContentType.ToString().ToLower()) == "image/gif")
        {
            return System.Drawing.Imaging.ImageFormat.Gif;
        }
        else if ((strContentType.ToString().ToLower()) == "image/bmp")
        {
            return System.Drawing.Imaging.ImageFormat.Bmp;
        }
        else if ((strContentType.ToString().ToLower()) == "image/tiff")
        {
            return System.Drawing.Imaging.ImageFormat.Tiff;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-icon")
        {
            return System.Drawing.Imaging.ImageFormat.Icon;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-png")
        {
            return System.Drawing.Imaging.ImageFormat.Png;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-emf")
        {
            return System.Drawing.Imaging.ImageFormat.Emf;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-exif")
        {
            return System.Drawing.Imaging.ImageFormat.Exif;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-wmf")
        {
            return System.Drawing.Imaging.ImageFormat.Wmf;
        }
        else
        {
            return System.Drawing.Imaging.ImageFormat.MemoryBmp;
        }
    }

    private void GetThumbNail(string strFileName, int iWidth, int iheight,
        string strContentType, bool blnGetFromFile, System.IO.Stream ImgStream)
    {
        System.Drawing.Image oImg;

        if (blnGetFromFile)
        {
            oImg = System.Drawing.Image.FromFile(strFileName);
        }
        else
        {
            oImg = System.Drawing.Image.FromStream(ImgStream);
        }
        oImg = oImg.GetThumbnailImage(iWidth, iheight, null, IntPtr.Zero);
        string strGuid = System.Guid.NewGuid().ToString().ToUpper();
        string strFileExt = strFileName.Substring(strFileName.LastIndexOf("."));
        Response.ContentType = strContentType;
        MemoryStream MemStream = new MemoryStream();
        oImg.Save(MemStream, GetImageType(strContentType));
        MemStream.WriteTo(Response.OutputStream);
    }
}