[使用FileStream ASPNET发送500MB大文件时出现OutOfMemoryException

Question

我正在使用Filestream读取大文件（> 500 MB），并且收到OutOfMemoryException。

我使用Asp.net，.net 3.5，win2003，iis 6.0

我想要在我的应用程序中使用这个：]

从Oracle读取数据

使用FileStream和BZip2解压缩文件

读取未压缩的文件，并将其发送到asp.net页面进行下载。

当我从磁盘读取文件时，失败！！！并获取OutOfMemory ...

。我的代码是：

using (var fs3 = new FileStream(filePath2, FileMode.Open, FileAccess.Read)) 
        { 
          byte[] b2 = ReadFully(fs3, 1024); 
        } 

 // http://www.yoda.arachsys.com/csharp/readbinary.html
 public static byte[] ReadFully(Stream stream, int initialLength) 
  { 
    // If we've been passed an unhelpful initial length, just 
    // use 32K. 
    if (initialLength < 1) 
    { 
      initialLength = 32768; 
    } 

    byte[] buffer = new byte[initialLength]; 
    int read = 0; 

    int chunk; 
    while ((chunk = stream.Read(buffer, read, buffer.Length - read)) > 0) 
    { 
      read += chunk; 

      // If we've reached the end of our buffer, check to see if there's 
      // any more information 
      if (read == buffer.Length) 
      { 
        int nextByte = stream.ReadByte(); 

        // End of stream? If so, we're done 
        if (nextByte == -1) 
        { 
          return buffer; 
        } 

        // Nope. Resize the buffer, put in the byte we've just 
        // read, and continue 
        byte[] newBuffer = new byte[buffer.Length * 2]; 
        Array.Copy(buffer, newBuffer, buffer.Length); 
        newBuffer[read] = (byte)nextByte; 
        buffer = newBuffer; 
        read++; 
      } 
    } 
    // Buffer is now too big. Shrink it. 
    byte[] ret = new byte[read]; 
    Array.Copy(buffer, ret, read); 
    return ret; 
  } 
现在，我更好地说明我的问题。

使用FileStream和BZip2解压缩文件就可以了，没事。

问题如下：

以字节[]读取磁盘中的大文件（> 500 MB），然后将字节发送到Response（asp.net）进行下载。

使用时

http://www.yoda.arachsys.com/csharp/readbinary.html

public static byte[] ReadFully
我收到错误：OutOfMemoryException ...

如果BufferedStream比Stream（FileStream，MemoryStream，...）更好？

使用BufferedStream，我可以读取700 MB的大文件吗？ （使用BufferedStream下载大文件的任何示例代码源）

我认为，这是一个问题：不是“如何将500mb文件读入内存？” ，但是“如何将大文件发送到ASPNET Response流？”

我由Cheeso找到此代码：

using (var fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))  
{  
   Response.BufferOutput= false;   // to prevent buffering 
   byte[] buffer = new byte[1024]; 
   int bytesRead = 0; 
   while ((bytesRead = fs.Read(buffer, 0, buffer.Length)) > 0)  
   { 
       Response.OutputStream.Write(buffer, 0, bytesRead); 
   } 
}
是好的代码吗？对高性能的任何改进？
一个同事说我，使用

Response.TransmitFile(filePath);
现在，另一个问题，更好的TransmitFile或Cheeso的代码??
很多年前，在《 msdn》杂志上刊登了有关它的好文章，但我无法访问http://msdn.microsoft.com/msdnmag/issues/06/09/WebDownloads/，

更新

：您可以使用链接https://web.archive.org/web/20070627063111/http://msdn.microsoft.com/msdnmag/issues/06/09/WebDownloads/]中的webarchive进行访问。

任何建议，评论，示例代码源？

我正在使用Filestream读取大文件（> 500 MB），并且收到OutOfMemoryException。我使用Asp.net，.net 3.5，win2003，iis 6.0在我的应用程序中需要这样做：使用...

<<<我已经创建了下载页面，该页面允许用户在几个月前下载高达4GB（可能更多）的文件。这是我的工作片段：

  private void TransmitFile(string fullPath, string outFileName)
    {
        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 = fullPath;

        // 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);


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

            Response.Clear();
            Response.ContentType = "application/octet-stream";
            Response.AddHeader("Content-Disposition", "attachment; filename=" + outFileName);
            Response.AddHeader("Content-Length", iStream.Length.ToString());

            // 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 output.
                    Response.Flush();

                    buffer = new Byte[10000];
                    dataToRead = dataToRead - length;
                }
                else
                {
                    //prevent infinite loop if user disconnects
                    dataToRead = -1;
                }
            }
        }
        catch (Exception ex)
        {
            throw new ApplicationException(ex.Message);
        }
        finally
        {
            if (iStream != null)
            {
                //Close the file.
                iStream.Close();
            }
            Response.Close();
        }
    }

您不需要将整个文件保存在内存中，只需读取它并循环写入响应流。

Answer 1

Answer 2

1-使用RecyclableMemoryStream代替MemoryStream解决方案

Answer 3

/// <summary>Based upon https://stackoverflow.com/a/3363015/595473 </summary>
public class BufferedFileStreamResult : System.Web.Mvc.FileStreamResult
{
    public BufferedFileStreamResult(System.IO.Stream stream, string contentType, string fileDownloadName)
        : base(stream, contentType)
    {
        FileDownloadName = fileDownloadName;
    }

    public int BufferSize { get; set; } = 16 * 1024 * 1024;//--16MiB

    protected override void WriteFile(System.Web.HttpResponseBase response)
    {
        try
        {
            response.Clear();
            response.AddHeader("Content-Disposition", $"attachment; filename={FileDownloadName}");
            response.AddHeader("Content-Length", FileStream.Length.ToString());

            byte[] buffer;
            int bytesRead;

            while (response.IsClientConnected)//--Prevent infinite loop if user disconnects
            {
                buffer = new byte[BufferSize];

                //--Read the data in buffer
                if ((bytesRead = FileStream.Read(buffer, 0, BufferSize)) == 0)
                {
                    break;//--Stop writing if there's nothing left to write
                }

                //--Write the data to the current output stream
                response.OutputStream.Write(buffer, 0, bytesRead);

                //--Flush the data to the output
                response.Flush();
            }
        }
        finally
        {
            FileStream?.Close();
            response.Close();
        }
    }
}