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c#多图片上传并生成缩略图的实例代码

发布时间：2023-03-05 11:19:34 来源：互联网

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前台代码:

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="upload.aspx.cs" Inherits="upload" %><!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
 <title></title>
 <style type="text/css">
 li
 {
 list-style: none;
 padding-top: 10px;
 }
 </style>
 <script type="text/javascript" src="js/jquery-1.6.2.min.js"></script>
 <script type="text/javascript">
 function ValidImage(id, msg) {
 $(id).parent().append("<span>" + msg + "</span>");
 return false;
 }
 </script>
</head>
<body>
 <form id="form1" runat="server" enctype="multipart/form-data" method="post">
 <div>
 <ul>
 <li>
 <input type="file" id="upload1" name="upload" />
 </li>
 <li>
 <input type="file" id="upload2" name="upload" />
 </li>
 <li>
 <input type="file" id="upload3" name="upload" />
 </li>
 <li>
 <input type="file" id="upload4" name="upload" /></li>
 <li>
 <input type="file" id="upload5" name="upload" /> </li>
 <li>
 <input type="submit" id="btnPostFile" runat="server" onserverclick="btnPostFile_ServerClick" value="开始上传" />
 </li>
 </ul>
 </div>
 </form>
</body>
</html>

前台就是几个控件和一个ValidImage方法。

后台代码：

 protected void btnPostFile_ServerClick(object sender, EventArgs e)
 {
 string filePath = Server.MapPath("/uploadImg");
 const int size = 5242880;
 if (!Directory.Exists(filePath))
 {
 Directory.CreateDirectory(filePath);
 }
 if (Request.Files.Count > 0)
 {
 for (int i = 0; i < Request.Files.Count; i++)
 {
 HttpPostedFile postFile = Request.Files[i];
 string uploadFileID = string.Format("#upload{0}", i + 1); //当前的上传控件ID,因为jquery要调用就加了#
 string msg = null; //提示信息
 if (postFile.FileName.Trim().Length <= 0)
 {
 continue;
 }
 if (postFile.ContentLength > size)
 {
 msg = "文件太大";
 Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);//将提示信息发送到客户端
 continue;
 }
 string savePath = Path.Combine(filePath, postFile.FileName); //图片的保存地址
 if (!File.Exists(savePath))
 {
 postFile.SaveAs(Path.Combine(filePath, postFile.FileName)); //如果文件不存在就保存
 }
 else
 {
 msg = "文件" + postFile.FileName + "已经存在";
 Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);//将提示信息发送到客户端
 continue;
 }
 if (IsImg(savePath)) //通过IsImg方法验证文件是否是图片，或者格式是否正确
 {
 SmallImg(postFile.InputStream, postFile.FileName);
 }
 else
 {
 msg = "只能上传JGP、PNG类型的图片，请检查文件格式是否正确";
 Page.ClientScript.RegisterStartupScript(GetType(), "", "ValidImage(" + uploadFileID + "," + msg + ")", true);//将提示信息发送到客户端
 File.Delete(savePath); //如果不是图片就删除
 }
 }
 }
 }


 #region 验证上传文件的格式
 /// <summary>
 /// 验证上传文件是否是图片
 /// </summary>
 /// <param name="FilePath">文件的保存路径</param>
 /// <returns></returns>
 private bool IsImg(string FilePath)
 {
 using (FileStream fs = new FileStream(FilePath, FileMode.Open, FileAccess.Read))
 {
 bool result = false;
 BinaryReader br = new BinaryReader(fs, System.Text.Encoding.UTF8);
 string strImg = "";
 byte buffer;
 try
 {
 buffer = br.ReadByte();
 strImg = buffer.ToString();
 buffer = br.ReadByte();
 strImg += buffer.ToString();
 }
 catch
 {
 fs.Close();
 br.Close(); }
 if (strImg == "255216" || strImg == "13780")//说明255216是jpg;7173是gif;6677是BMP,13780是PNG;7790是exe,8297是rar
 {
 result = true;
 }
 return result;
 }
 }
 #endregion

 #region 将图片生成缩略图
 /// <summary>
 /// 生成缩略图
 /// </summary>
 private void SmallImg(Stream oStream, string FileName)
 {
 using (System.Drawing.Image img = System.Drawing.Image.FromStream(oStream))
 {
 int newWidth = 100;
 int newHeight = 80;
 int oldWidth = img.Width;
 int oldHeight = img.Height;
 if (oldWidth > oldHeight)
 {
 newHeight = (int)Math.Floor((double)oldHeight * (double)newWidth / (double)oldWidth);
 }
 else
 {
 newWidth = (int)Math.Floor((double)oldWidth * (double)newHeight / (double)oldHeight);
 }
 using (Bitmap bmp = new Bitmap(newWidth, newHeight))
 {
 using (Graphics g = Graphics.FromImage(bmp))
 {
 g.Clear(Color.Transparent);
 g.InterpolationMode = InterpolationMode.High;
 g.CompositingQuality = CompositingQuality.HighQuality;
 g.SmoothingMode = SmoothingMode.HighQuality;
 g.DrawImage(img, new Rectangle(0, 0, newWidth, newHeight), new Rectangle(0, 0, oldWidth, oldHeight), GraphicsUnit.Pixel);
 string newFileName = Path.GetFileNameWithoutExtension(FileName) + "_small" + Path.GetExtension(FileName); //缩略图名称
 string filePath = Server.MapPath("/uploadImg/") + newFileName;
 bmp.Save(filePath);
 }
 } }
 }
 #endregion