定义无图片时显示默认图片，大小

<%@ Control Language="C#" AutoEventWireup="true" CodeFile="ImageThumbnail.ascx.cs" Inherits="ImageThumbnail" %>
<asp:Image ID="Image1" runat="server" CssClass="photo" BorderWidth="1" />

 1using System;
 2
 3public partial class ImageThumbnail : System.Web.UI.UserControl
 4{
 5    public object PhotoID
 6    {
 7        get
 8        {
 9            object o = ViewState["PhotoID"];
10            return (o != null) ? (int)o : 0;
11        }
12        set
13        {
14            ViewState["PhotoID"] = (value != null && value != DBNull.Value) ? Convert.ToInt32(value) : 0;
15        }
16    }
17    public ImageSizes ImageSize
18    {
19        get
20        {
21            object o = ViewState["ImageSize"];
22            return (o != null) ? (ImageSizes)o : ImageSizes.Thumb;
23        }
24        set
25        {
26            ViewState["ImageSize"] = value;
27        }
28    }
29    public enum ImageSizes
30    {
31        Large = 0,
32        Thumb = 1,
33        FullSize = 2
34    }
35    public string NoPhotoImg
36    {
37        get
38        {
39            object o = ViewState["NoPhotoImg"];
40            return (o != null) ? (string)o : null;
41        }
42        set
43        {
44            ViewState["NoPhotoImg"] = value;
45        }
46    }
47    protected void Page_PreRender(object sender, System.EventArgs e)
48    {
49        if (Convert.ToInt32(PhotoID) == 0)
50        {
51            if (NoPhotoImg != null)
52            {
53                Image1.ImageUrl = NoPhotoImg;
54            }
55            else
56            {
57                Image1.Visible = false;
58            }
59        }
60        else
61        {
62            Image1.ImageUrl = "ImageFetch.ashx?Size=" + Convert.ToInt32(ImageSize) + "&ImageID=" + Convert.ToString(PhotoID);
63        }
64    }
65    protected void Page_Load(object sender, EventArgs e)
66    {
67
68    }
69}
70

ImageFetch.ashx

 1<%@ WebHandler Language="C#" Class="ImageFetch" %>
 2
 3using System;
 4using System.Web;
 5using System.Data.SqlClient;
 6using System.Data;
 7using System.IO;
 8
 9public class ImageFetch : IHttpHandler
10{
11    const int BUFFERSIZE = 1024;
12
13    public bool IsReusable
14    {
15        get
16        {
17            return true;
18        }
19    }
20
21    public void ProcessRequest(HttpContext context)
22    {
23        HttpResponse response = context.Response;
24        HttpRequest request = context.Request;
25        response.ContentType = "image/jpeg";
26        response.Cache.SetCacheability(HttpCacheability.Public);
27        response.BufferOutput = false;
28        writeSingleImage(Convert.ToInt32(request.QueryString["ImageID"]), Convert.ToInt32(request.QueryString["Size"]), response.OutputStream);
29        response.End();
30    }
31
32    public void writeSingleImage(int ImageID, int size, Stream output)
33    {
34        string cxnstr = System.Configuration.ConfigurationManager.ConnectionStrings["ClubSiteDB"].ConnectionString;
35        SqlConnection connection = new SqlConnection(cxnstr);
36        string query;
37        if (size == 0)
38        {
39            query = "select largeimage from images where id=@item_id";
40        }
41        else if (size == 1)
42        {
43            query = "select thumbimage from images where id=@item_id";
44        }
45        else if (size == 2)
46        {
47            query = "select origimage from images where id=@item_id";
48        }
49        else
50        {
51            query = "select largeimage from images where id=@item_id";
52        }
53        SqlCommand command = new SqlCommand(query, connection);
54        SqlParameter param0 = new SqlParameter("@item_id", SqlDbType.Int);
55        param0.Value = ImageID;
56        command.Parameters.Add(param0);
57        connection.Open();
58
59        byte[] d = ((byte[])(command.ExecuteScalar()));
60        output.Write(d, 0, d.Length);
61        connection.Close();
62    }
63}