我有一个内存大小为42 MB的大文件。我想以较少的内存消耗下载文件 控制器代码
public ActionResult Download()
{
var filePath = "file path in server";
FileInfo file = new FileInfo(filePath);
Response.ContentType = "application/zip";
Response.AppendHeader("Content-Disposition", "attachment; filename=folder.zip");
Response.TransmitFile(file.FullName);
Response.End();
}
使用 Stream
public ActionResult Download()
{
string failure = string.Empty;
Stream stream = null;
int bytesToRead = 10000;
long LengthToRead;
try
{
var path = "file path from server";
FileWebRequest fileRequest = (FileWebRequest)FileWebRequest.Create(path);
FileWebResponse fileResponse = (FileWebResponse)fileRequest.GetResponse();
if (fileRequest.ContentLength > 0)
fileResponse.ContentLength = fileRequest.ContentLength;
//Get the Stream returned from the response
stream = fileResponse.GetResponseStream();
LengthToRead = stream.Length;
//Indicate the type of data being sent
Response.ContentType = "application/octet-stream";
//Name the file
Response.AddHeader("Content-Disposition", "attachment; filename=SolutionWizardDesktopClient.zip");
Response.AddHeader("Content-Length", fileResponse.ContentLength.ToString());
int length;
do
{
// Verify that the client is connected.
if (Response.IsClientConnected)
{
byte[] buffer = new Byte[bytesToRead];
// Read data into the buffer.
length = stream.Read(buffer, 0, bytesToRead);
// and write it out to the response's output stream
Response.OutputStream.Write(buffer, 0, length);
// Flush the data
Response.Flush();
//Clear the buffer
LengthToRead = LengthToRead - length;
}
else
{
// cancel the download if client has disconnected
LengthToRead = -1;
}
} while (LengthToRead > 0); //Repeat until no data is read
}
finally
{
if (stream != null)
{
//Close the input stream
stream.Close();
}
Response.End();
Response.Close();
}
return View("Failed");
}
由于文件的大小，它会消耗更多内存，从而导致性能问题 在检查iis日志后，下载过程分别为42 mb和64 mb 提前致谢
答案 0 :(得分：18)
更好的选择是使用FileResult而不是ActionResult：
使用此方法意味着您不必在服务之前将文件/字节加载到内存中。
public FileResult Download()
{
var filePath = "file path in server";
return new FilePathResult(Server.MapPath(filePath), "application/zip");
}
编辑：对于较大的文件，FilePathResult也会失败。
你最好的选择可能就是Response.TransmitFile（）。我已经在较大的文件（GB）上使用它，并且在
之前没有问题public ActionResult Download()
{
var filePath = @"file path from server";
Response.Clear();
Response.ContentType = "application/octet-stream";
Response.AppendHeader("Content-Disposition", "filename=" + filePath);
Response.TransmitFile(filePath);
Response.End();
return Index();
}
来自MSDN：
将指定文件直接写入HTTP响应输出流， 没有在内存中缓冲它。
答案 1 :(得分：3)
尝试将Transfer-Encoding标头设置为chunked，并返回带有PushStreamContent的HttpResponseMessage。分块的传输编码意味着HTTP响应不具有Content-Length头，因此客户端必须将HTTP响应的块作为流进行解析。请注意，我从未遇到过没有处理传输编码分块的客户端（浏览器等）。您可以在以下链接中阅读更多内容。
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Transfer-Encoding
[HttpGet]
public async Task<HttpResponseMessage> Download(CancellationToken token)
{
var response = new HttpResponseMessage(System.Net.HttpStatusCode.OK)
{
Content = new PushStreamContent(async (stream, context, transportContext) =>
{
try
{
using (var fileStream = System.IO.File.OpenRead("some path to MyBigDownload.zip"))
{
await fileStream.CopyToAsync(stream);
}
}
finally
{
stream.Close();
}
}, "application/octet-stream"),
};
response.Headers.TransferEncodingChunked = true;
response.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
{
FileName = "MyBigDownload.zip"
};
return response;
}
答案 2 :(得分：3)
我有类似的问题，但我没有在本地磁盘上存档，我不得不从API下载它（我的MVC就像一个代理）。
关键是在MVC Action上设置Response.Buffer=false;。我认为@ JanusPienaar的第一个解决方案应该适用于此。
我的MVC行动是：
public class HomeController : Controller
{
public async Task<FileStreamResult> Streaming(long RecordCount)
{
HttpClient Client;
System.IO.Stream Stream;
//This is the key thing
Response.Buffer=false;
Client = new HttpClient() { BaseAddress=new Uri("http://MyApi", };
Stream = await Client.GetStreamAsync("api/Streaming?RecordCount="+RecordCount);
return new FileStreamResult(Stream, "text/csv");
}
}
我的测试WebApi（生成文件）是：
public class StreamingController : ApiController
{
// GET: api/Streaming/5
public HttpResponseMessage Get(long RecordCount)
{
var response = Request.CreateResponse();
response.Content=new PushStreamContent((stream, http, transport) =>
{
RecordsGenerator Generator = new RecordsGenerator();
long i;
using(var writer = new System.IO.StreamWriter(stream, System.Text.Encoding.UTF8))
{
for(i=0; i<RecordCount; i++)
{
writer.Write(Generator.GetRecordString(i));
if(0==(i&0xFFFFF))
System.Diagnostics.Debug.WriteLine($"Record no: {i:N0}");
}
}
});
return response;
}
class RecordsGenerator
{
const string abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char[] Chars = new char[14];//Ceiling(log26(2^63))
public string GetRecordString(long Record)
{
int iLength = 0;
long Div = Record, Mod;
do
{
iLength++;
Div=Math.DivRem(Div, abc.Length, out Mod);
//Save from backwards
Chars[Chars.Length-iLength]=abc[(int)Mod];
}
while(Div!=0);
return $"{Record} {new string(Chars, Chars.Length-iLength, iLength)}\r\n";
}
}
}
}
如果RecordCount为100000000，则TestApi生成的文件为1.56 GB。 WebApi和MVC都没有消耗太多内存。
答案 3 :(得分：1)
您只需使用IIS启用HTTP下载即可查看此link
，您只需要返回文件的HTTP路径即可快速轻松地下载。
答案 4 :(得分：1)
在某些情况下，您需要为服务器上某处或运行时生成的大文件提供下载选项。以下功能可用于下载任何大小的文件。有时下载大文件会引发OutOfMemoryException异常，显示“内存不足，无法继续执行程序”。因此，此功能还可以通过将文件拆分为1 MB的块（可以通过更改bufferSize变量进行自定义）来处理这种情况。
用法：
DownloadLargeFile("A big file.pdf", "D:\\Big Files\\Big File.pdf", "application/pdf", System.Web.HttpContext.Current.Response);
您可以通过右侧Rizwan Ansari更改“ application / pdf”
下载功能：
public static void DownloadLargeFile(string DownloadFileName, string FilePath, string ContentType, HttpResponse response)
{
Stream stream = null;
// read buffer in 1 MB chunks
// change this if you want a different buffer size
int bufferSize = 1048576;
byte[] buffer = new Byte[bufferSize];
// buffer read length
int length;
// Total length of file
long lengthToRead;
try
{
// Open the file in read only mode
stream = new FileStream(FilePath, FileMode.Open, FileAccess.Read, FileShare.Read);
// Total length of file
lengthToRead = stream.Length;
response.ContentType = ContentType;
response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(DownloadFileName, System.Text.Encoding.UTF8));
while (lengthToRead > 0)
{
// Verify that the client is connected.
if (response.IsClientConnected)
{
// Read the data in buffer
length = stream.Read(buffer, 0, bufferSize);
// Write the data to output stream.
response.OutputStream.Write(buffer, 0, length);
// Flush the data
response.Flush();
//buffer = new Byte[10000];
lengthToRead = lengthToRead - length;
}
else
{
// if user disconnects stop the loop
lengthToRead = -1;
}
}
}
catch (Exception exp)
{
// handle exception
response.ContentType = "text/html";
response.Write("Error : " + exp.Message);
}
finally
{
if (stream != null)
{
stream.Close();
}
response.End();
response.Close();
}
}