ashx源文件代码：

<%@ WebHandler Language="C#" Class="GetThumbnailImageByEmpCode" %>using System;
using System.Web;
using System.Data.SqlClient;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.IO;
using System.Drawing.Imaging;public class GetThumbnailImageByEmpCode : IHttpHandler
{public void ProcessRequest(HttpContext context){if (context.Request.QueryString["code"] == null){return;}int newWidth = 336;         //目标图片宽度int newHeight = 252;        //目标图片高度bool bNeedUpdate = false;   //是否需要更新数据库System.Drawing.Image Img;using (SqlConnection conn = new SqlConnection(db.ConnectionStrings.hrConnectionString))using (SqlCommand cmd = new SqlCommand("", conn)){cmd.CommandText = "select photo from ZlEmployee where code=@code and DATALENGTH(photo)>1000";cmd.Parameters.AddWithValue("code", context.Request.QueryString["code"]);conn.Open();SqlDataReader reader = cmd.ExecuteReader();if (reader.Read()){byte[] imgData = (byte[])reader[0];reader.Close();using (MemoryStream ms = new MemoryStream(imgData)){Img = System.Drawing.Image.FromStream(ms);}if (Img.Width > newWidth || Img.Height > newHeight){Img = reSizeImage(Img);bNeedUpdate = true;}using (MemoryStream ms = new MemoryStream()){#region 输出图片到浏览器Bitmap jpg = new Bitmap(Img);jpg.Save(ms, ImageFormat.Jpeg);context.Response.Clear();context.Response.Charset = "utf-8";context.Response.ContentType = "image/pjpeg";context.Response.BinaryWrite(ms.ToArray());#endregion//检查是否需要更新if (bNeedUpdate){cmd.CommandText = "update ZlEmployee set photo=@photo where code=@code";cmd.Parameters.Clear();cmd.Parameters.AddWithValue("code", context.Request.QueryString["code"]);cmd.Parameters.AddWithValue("photo", ms.ToArray());cmd.ExecuteNonQuery();}}context.Response.End();}}}public System.Drawing.Image reSizeImage(System.Drawing.Image img){int newWidth = 336;int newHeight = 252;//如果是高度大于宽度则按竖图处理，宽小于高if (img.Height > img.Width){newWidth = 252;newHeight = 336;}#region 计算按比例缩放的图片尺寸if (img.Height / img.Width > newHeight / newWidth){newWidth = newHeight * img.Width / img.Height;}else{newHeight = img.Height * newWidth / img.Width;}#endregion#region 缩放图片using (System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap((int)newWidth, (int)newHeight, PixelFormat.Format32bppArgb)) //using   3 {using (System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(bitmap)){//清除整个绘图面并以透明背景色填充 graphics.Clear(Color.Transparent);//在指定位置并且按指定大小绘制   原图片   对象 graphics.DrawImage(img, new Rectangle(0, 0, (int)newWidth, (int)newHeight));using (MemoryStream ms = new MemoryStream()){bitmap.Save(ms, ImageFormat.Jpeg);return System.Drawing.Image.FromStream(ms);}}}#endregion}public bool IsReusable{get{return false;}}
}