本文介绍了一种在ASP.NET中下载文件的方法。 方法一：可能是最简单的、最短的方式：
1 Response.ContentType = "application/pdf";
2 Response.AppendHeader("Content-Disposition", "attachment; filename=MyFile.pdf");
3 Response.TransmitFile(Server.MapPath("~/Files/MyFile.pdf"));
4 Response.End();
第一步是设置文档内容的类型，上面的例子是下载一个.PDF格式的文件。下面是最常用的一些文档内容类型：
.htm,
.html Response.ContentType =
"text/HTML";
.txt Response.ContentType =
"text/plain";
.doc,
.rtf, .docx Response.ContentType =
"Application/msword";
.xls,
.xlsx Response.ContentType =
"Application/x-msexcel";
.jpg,
.jpeg Response.ContentType =
"image/jpeg";
.gif
Response.ContentType = "image/GIF";
.pdf Response.ContentType =
"application/pdf";
方法二：解决.PDF文件较大时，可能导致所下载的PDF文件无法打开的方案
1 protected void Button1_Click(object sender, EventArgs e)
2 {
3 string path;
4 try
5 {
6 path = Request.PhysicalApplicationPath + "/" + Session["pdfpath"].ToString() + "/PDF/" + Session["mlmc"].ToString() + ".pdf";
7 }
8 catch (Exception)
9 {
10 return;
11 }
12 System.IO.Stream iStream = null;
13 byte[] buffer = new Byte[10000];
14 int length;
15 long dataToRead;
16 string filename = Session["mlmc"].ToString() + ".pdf";
17
18 try
19 {
20 iStream = new System.IO.FileStream(path, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.Read);
21 dataToRead = iStream.Length;
22 Response.Clear();
23 Response.ClearHeaders();
24 Response.ClearContent();
25 Response.ContentType = "application/pdf"; //文件类型
26 Response.AddHeader("Content-Length", dataToRead.ToString());//添加文件长度，进而显示进度
27 Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));
28 while (dataToRead > 0)
29 {
30 if (Response.IsClientConnected)
31 {
32 length = iStream.Read(buffer, 0, 10000);
33 Response.OutputStream.Write(buffer, 0, length);
34 Response.Flush();
35
36 buffer = new Byte[10000];
37 dataToRead = dataToRead - length;
38 }
39 else
40 {
41 dataToRead = -1;
42 }
43 }
44
45 }
46 catch (Exception ex)
47 {
48 Response.Write("文件下载时出现错误!");
49 }
50 finally
51 {
52 if (iStream != null)
53 {
54 iStream.Close();
55 }
56 //结束响应，否则将导致网页内容被输出到文件，进而文件无法打开
57 Response.End();
58 }
59 }
通过以上代码，可在浏览器中打开一个“打开/保存”对话框来下载并保存文件。