ASP.NET 实现文件下载的几种方法

一、调用 TransmitFile 方法。

缺点：对于浏览器能解析的文件类型，不会弹出保存框，直接被浏览器显示。例如：TXT,XML等

代码样例：

Response.ContentType = "application/x-zip-compressed";
Response.AddHeader("Content-Disposition", "attachment;filename=test.zip");
string filename = Server.MapPath("DownLoad/test.zip");
Response.TransmitFile(filename);

二、调用 WritFile 方法

缺点同上。

代码样例：

string fileName ="aaa.zip";//客户端保存的文件名
string filePath=Server.MapPath("DownLoad/aaa.zip");//路径
FileInfo fileInfo = new FileInfo(filePath);
Response.Clear();
Response.ClearContent();
Response.ClearHeaders();
Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.AddHeader("Content-Length", fileInfo.Length.ToString());
Response.AddHeader("Content-Transfer-Encoding", "binary");
Response.ContentType = "application/octet-stream";
Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
Response.WriteFile(fileInfo.FullName);
Response.Flush();
Response.End();

三、分块下载

特点：适合传输大文件。没有浏览器直接显示文件的缺点。

string fileName = "aaa.zip";//客户端保存的文件名
string filePath = Server.MapPath("DownLoad/aaa.zip");//路径
System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);
if (fileInfo.Exists == true)
{
const long ChunkSize = 102400;//100K 每次读取文件，只读取100Ｋ，这样可以缓解服务器的压力
byte[] buffer = new byte[ChunkSize];
Response.Clear();
System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
long dataLengthToRead = iStream.Length;//获取下载的文件总大小
Response.ContentType = "application/octet-stream";
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName));
while (dataLengthToRead > 0 && Response.IsClientConnected)
{
int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
Response.OutputStream.Write(buffer, 0, lengthRead);
Response.Flush();
dataLengthToRead = dataLengthToRead - lengthRead;
}
Response.Close();
}

 

四、BinaryWrite 方法

特点:与方法三一样避免了浏览器的直接解析，也是通过二进制流传输，但是不是分块提供下载，而是整个文件一次传输，适合下载小文件。

代码样例：

五、ContentType设置改进

ASP.NET中设置文件下载总结起来就是三个步骤：

1.设置Response的报文头。

最主要的是设置Content-Type,Content-Disposition

2.读出文件，写入Response流

3.发送，也就是先Flush,再End.

在这里有一个根据系统注册表自动设置文件Content-Type的方法：

string saveFileName = "test.exe";
int intStart = filename.LastIndexOf("\") + 1;
saveFileName = filename.Substring(intStart, filename.Length - intStart);
System.IO.FileInfo fi = new System.IO.FileInfo(filename);
string fileextname = fi.Extension;
string DEFAULT_CONTENT_TYPE = "application/unknown";
RegistryKey regkey, fileextkey;
string filecontenttype;
try
{
regkey = Registry.ClassesRoot;
fileextkey = regkey.OpenSubKey(fileextname);
filecontenttype = fileextkey.GetValue("Content Type", DEFAULT_CONTENT_TYPE).ToString();
}
catch
{
filecontenttype = DEFAULT_CONTENT_TYPE;
}
Response.Clear();
Response.Charset = "utf-8";
Response.Buffer = true;
this.EnableViewState = false;
Response.ContentEncoding = System.Text.Encoding.UTF8;
Response.AppendHeader("Content-Disposition", "attachment;filename=" + saveFileName);
Response.ContentType = filecontenttype;
Response.WriteFile(filename);
Response.Flush();
Response.Close();
Response.End();

string fileName = "aaa.zip";//客户端保存的文件名
string filePath = Server.MapPath("DownLoad/aaa.zip");//路径
//以字符流的形式下载文件
FileStream fs = new FileStream(filePath, FileMode.Open);
byte[] bytes = new byte[(int)fs.Length];
fs.Read(bytes, 0, bytes.Length);
fs.Close();
Response.Clear();
Response.ContentType = "application/octet-stream";
//通知浏览器下载文件而不是打开
Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8));
Response.BinaryWrite(bytes);
Response.Flush();
Response.End();

 

Tags - asp.net文件下载方法 , .net文件下载方法