C#从服务器下载大文件，占用内存更少
我有一个内存大小为42MB的大文件。我想以较少的内存消耗下载该文件。C#从服务器下载大文件，占用内存更少,c#,asp.net-mvc,stream,filestream,C#,Asp.net Mvc,Stream,Filestream,我有一个内存大小为42MB的大文件。我想以较少的内存消耗下载该文件。 控制器代码 public ActionResult Download() { var filePath = "file path in server"; FileInfo file = new FileInfo(filePath); Response.ContentType = "application/zip"; Response.AppendH
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();
}
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");
}
签入iis日志后，下载过程分别占用42 mb和64 mb。
提前感谢更好的选择是使用FileResult而不是ActionResult： 使用此方法意味着您不必在提供服务之前加载内存中的文件/字节
public FileResult Download()
{
var filePath = "file path in server";
return new FilePathResult(Server.MapPath(filePath), "application/zip");
}
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();
}
你只需要使用IIS来启用HTTP下载看看这个
您只需返回文件的HTTP路径，即可快速轻松地下载。尝试将传输编码头设置为chunked，并返回带有PushStreamContent的HttpResponseMessage。chunked的传输编码意味着HTTP响应将没有内容长度头，因此客户端必须将HTTP响应的块解析为流。注意，我从未遇到过不处理分块传输编码的客户端（浏览器等）。你可以在下面的链接上阅读更多内容
[HttpGet]
公共异步任务下载（CancellationToken令牌）
{
var响应=新的HttpResponseMessage（System.Net.HttpStatusCode.OK）
{
内容=新的PushStreamContent（异步（流、上下文、传输上下文）=>
{
尝试
{
使用（var fileStream=System.IO.File.OpenRead（“MyBigDownload.zip的某些路径”））
{
等待fileStream.CopyToAsync（流）；
}
}
最后
{
stream.Close（）；
}
}，“应用程序/八位字节流”），
};
response.Headers.transferncodingchunked=true；
response.Content.Headers.ContentDisposition=新系统.Net.Http.Headers.ContentDispositionHeaderValue（“附件”）
{
FileName=“MyBigDownload.zip”
};
返回响应；
}
Response.Buffer=false在您的MVC操作上。我认为@Janupienaar的第一个解决方案应该与此配合使用。
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");
}
}
公共类HomeController:控制器
{
公共异步任务流（长记录计数）
{
HttpClient；
System.IO.Stream；
//这是关键
Response.Buffer=false；
Client=new-HttpClient（）{BaseAddress=new-Uri（“http://MyApi", };
Stream=wait Client.GetStreamAsync（“api/Streaming？RecordCount=“+RecordCount”）；
返回新文件streamresult（流，“text/csv”）；
}
}
我的测试WebApi（生成文件）是：
公共类StreamingController:ApicController
{
//获取：api/Streaming/5
公共HttpResponseMessage获取（长记录计数）
{
var response=Request.CreateResponse（）；
response.Content=新的PushStreamContent（（流、http、传输）=>
{
RecordsGenerator Generator=新的RecordsGenerator（）；
龙我；
使用（var writer=new System.IO.StreamWriter（stream，System.Text.Encoding.UTF8））
{
对于（i=0；i有一个职位适合我：
在某些情况下，您需要为位于服务器某处或运行时生成的大文件提供下载选项。下面的函数可用于下载任何大小的文件。有时，下载大文件会抛出异常OutOfMemoryException，显示“内存不足，无法继续执行程序”。因此，此函数还通过将文件分解为1 MB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);
您可以在右边更改“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();
}
}
流是你的朋友有什么原因你不使用内置的操作结果只用于此场景，如FilePathResult/FileStreamResult等等？我使用ActionResult你使用IIS作为web服务器吗？我使用IIS作为web服务器。文件将放在c或d文件夹中。因此我认为我们不能使用“server.MapPath（）”ASP.NET Core 3.1中的“Response”与什么等效？它是HttpContext.Response（可在控制器上获得）我遇到了类似的问题（该文件来自API）。我找不到专门针对此问题的单独StackOverflow问题以及如此简单的解决方案。请将您的解决方案作为单独的问题进行分享，并将答案张贴在那里？
DownloadLargeFile("A big file.pdf", "D:\\Big Files\\Big File.pdf", "application/pdf", System.Web.HttpContext.Current.Response);
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();
}
}