如何用Response.ContentType控制输出的文件类型及相关讨论

以上文章转贴自http://www.w269.com/infow269/1145w2691.htm
这里我想讨论一下，这么也东东。

Q：如何利用ContentType 来，在服务器上提供一个.xls后缀的文件点击下载而不是直接在浏览器中打开。（注意：于上程序文件以XLS文件被提供下载有所不同）

Response.ContentType = “application/x-download”，让整个程序文件点击下载了。怎么办好呢？？？

A:解决方案1. 利用Response.WriteFile的文件输出操作
具体在按钮点击事件中添加一下代码
private void btnDownload_Click(object sender, System.EventArgs e)
  {

   string DownloadFileName=Server.MapPath(“file.xls”);
   string filepath = DownloadFileName;

   // Identify the file name.
   string filename = System.IO.Path.GetFileName(filepath);

   Response.Clear();

   // Specify the Type of the downloadable file.
   Response.ContentType = “application/octet-stream”;

   // Set the Default file name in the FileDownload dialog box.
   Response.AddHeader(“Content-Disposition”, “attachment; filename=” + filename);

   Response.Flush();

   // Download the file.
   Response.WriteFile(filepath);
  }
以上代码也适合用于小于100MB的小文件下载
如果是大于100MB的大文件下载可以用Response.FileStream 。

C#代码如下：（将 DownloadFileName 替换为大于 100 MB 的文件的名称。）

System.IO.Stream iStream = null;

// Buffer to read 10K bytes in chunk:
byte[] buffer = new Byte[10000];

// Length of the file:
int length;

// Total bytes to read:
long dataToRead;

// Identify the file to download including its path.
string filepath  = “DownloadFileName”;

// Identify the file name.
string  filename  = System.IO.Path.GetFileName(filepath);

try
{

// Open the file.
iStream = new System.IO.FileStream(filepath, System.IO.FileMode.Open,
System.IO.FileAccess.Read,System.IO.FileShare.Read);//用文件流来处理


// Total bytes to read:
dataToRead = iStream.Length;

Response.ContentType = “application/octet-stream”;//问题就在这里，解决百M关口
Response.AddHeader(“Content-Disposition”, “attachment; filename=” + filename);

// Read the bytes.
  while (dataToRead > 0)
{

// Verify that the client is connected.
if (Response.IsClientConnected)
{

// Read the data in buffer.
length = iStream.Read(buffer, 0, 10000);

// Write the data to the current output stream.
Response.OutputStream.Write(buffer, 0, length);

// Flush the data to the HTML output.
Response.Flush();

buffer= new Byte[10000];
dataToRead = dataToRead – length;
}
else
{

//prevent infinite loop if user disconnects
dataToRead = -1;
}
}
}
catch (Exception ex)
{

// Trap the error, if any.
Response.Write(“Error : ” + ex.Message);
}
finally
{

if (iStream != null)
{

//Close the file.
iStream.Close();
}
}
 
参考：PRB：Response.WriteFile 无法下载大文件
http://support.microsoft.com/default.aspx?scid=kb;zh-cn;812406#2