asp.net large file download out of memory exception - asp.net

Question

I'm trying to download a file with size greater than 50mb in an asp.net page. But it fails on our production server. It works on development and QA servers. I'm using the following code.
Response.Clear()
oBinaryReader = New System.IO.BinaryReader(System.IO.File.OpenRead(sDocPath))
lFileSize = Microsoft.VisualBasic.FileLen(sDocPath)
Response.AddHeader("Content-Disposition", "attachment;filename=" & sDownloadFileName)
Response.ContentType = "application/unknown"
Response.BinaryWrite(oBinaryReader.ReadBytes(lFileSize))
Response.Flush()
HttpContext.Current.ApplicationInstance.CompleteRequest()
Response.End()
The error I'm getting from the server is as below.
Page_Load System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
at System.IO.BinaryReader.ReadBytes(Int32 count)
at ExportDoc.Page_Load(Object sender, EventArgs e) in c:\sitename\ExportDoc.aspx.vb:line 87 Server Name
What is wrong with the code?

Answer 1

OutOfMemoryException commonly thrown when there is no available memory to perform such operation when handling both managed/unmanaged resources. Therefore, you need to use Using...End Using block wrapping around BinaryReader to guarantee immediate disposal of unmanaged resources after usage with IDisposable interface:
Response.Clear()
Using oBinaryReader As BinaryReader = New BinaryReader(File.OpenRead(sDocPath))
lFileSize = FileLen(sDocPath)
Response.AddHeader("Content-Disposition", "attachment;filename=" & sDownloadFileName)
Response.ContentType = "application/unknown"
Response.BinaryWrite(oBinaryReader.ReadBytes(lFileSize))
Response.Flush()
HttpContext.Current.ApplicationInstance.CompleteRequest()
Response.End()
End Using
Another common usage of BinaryReader is using FileStream and a byte buffer to control file reading mechanism:
Using FStream As FileStream = New FileStream(File.OpenRead(sDocPath))
lFileSize = CType(FStream.Length, Integer)
Dim Buffer() As Byte
Using oBinaryReader As BinaryReader = New BinaryReader(FStream)
Buffer = oBinaryReader.ReadBytes(lFileSize)
End Using
Response.Clear()
Response.AddHeader("Content-Disposition", "attachment;filename=" & sDownloadFileName)
Response.ContentType = "application/unknown"
Response.BinaryWrite(Buffer)
Response.Flush()
HttpContext.Current.ApplicationInstance.CompleteRequest()
Response.End()
End Using
References:
VB.NET Using Statement (MSDN)
BinaryReader Class (MSDN)

Answer 2

I tried the below code and it resolved my issue, found the code idea from MSDN website.
Using iStream As System.IO.Stream = New System.IO.FileStream(sDocPath, System.IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.Read)
dataToRead = iStream.Length
Response.ContentType = "application/octet-stream"
Response.AddHeader("Content-Disposition", "attachment; filename=" & filename)
While dataToRead > 0
If Response.IsClientConnected Then
length = iStream.Read(buffer, 0, bufferSize)
Response.OutputStream.Write(buffer, 0, length)
Response.Flush()
ReDim buffer(bufferSize)
dataToRead = dataToRead - length
Else
dataToRead = -1
End If
End While
HttpContext.Current.ApplicationInstance.CompleteRequest()
End Using