Getting Out of Memory Exception when downloading large files

Question

I developed ASP.NET web application. I am trying to download the document from file server. FileSize maybe more than 1GB.

Here the thing is, very first time file got downloaded. when i click the same link, i am getting "Out of memory Exception" throws error.

If it is small size file, i don't get any issues to download the filles...

How do we handle this error if i download the document more than 1GB...?

below is the code to download the file in ASP.NET (Code behind file)

 Dim binFile As Byte() = File.ReadAllBytes(filename)  
            Response.ContentType = "application/octet-stream"  
            Response.AppendHeader("Content-Disposition", "attachment; filename=" + filename)  
            Response.BinaryWrite(binFile)  
            Response.End()  

Answer 1

Hi @BeUnique ,
If you only need a file download handler, use HttpResponse.TransmitFile() which don't buffer the file in memory.
https://learn.microsoft.com/en-us/dotnet/api/system.web.httpresponse.transmitfile?redirectedfrom=MSDN&view=netframework-4.8#System_Web_HttpResponse_TransmitFile_System_String_
Or try the code below, the meaning of the code is written in the comments.

Public Sub Download(ByVal fileId As String)  
     //MAKE FILEPATH  
    Dim filePath As String = makeFilePath(fileId)  
    Dim outFileName As String = _info.FileName  
    Dim iStream As System.IO.Stream = Nothing  
    // Create buffer for reading [intBufferSize] bytes from file  
    Dim intBufferSize As Integer = 10 * 1024  
    Dim buffer As Byte() = New System.Byte(intBufferSize - 1) {}  
    // Length of the file That Really Has Been Read From The Stream and Total bytes to read  
    Dim length As Integer  
    Dim dataToRead As Long  
  
    If System.IO.File.Exists(filePath) Then  
  
        Try  
            // Open the file.  
            iStream = New System.IO.FileStream(path:=filePath, mode:=System.IO.FileMode.Open, access:=System.IO.FileAccess.Read, share:=System.IO.FileShare.Read)  
            // Total bytes to read:  
            dataToRead = iStream.Length  
            Response.Clear()  
             // Setting the unknown [ContentType]  
             // will display the saving dialog for the user  
            Response.ContentType = "application/octet-stream"  
            // With setting the file name,  
            // in the saving dialog, user will see  
            // the [outFileName] name instead of [download]!  
            Response.AddHeader("Content-Disposition", "attachment; filename=" & outFileName)  
            // Notify user (client) the total file length  
            Response.AddHeader("Content-Length", iStream.Length.ToString())  
             // Read the bytes.  
            While dataToRead > 0  
                 // Verify that the client is connected.  
                If Response.IsClientConnected Then  
                    // Read the data and put it in the buffer.  
                    length = iStream.Read(buffer:=buffer, offset:=0, count:=intBufferSize)  
                   // Write the data from buffer to the current output stream.  
                    Response.OutputStream.Write(buffer:=buffer, offset:=0, count:=length)  
                     // Flush (Send) the data to output  
                     // (Don't buffer in server's RAM!)  
                    Response.Flush()  
                    buffer = New Byte(intBufferSize - 1) {}  
                    dataToRead = dataToRead - length  
                Else  
                    //prevent infinite loop if user disconnects  
                    dataToRead = -1  
                End If  
            End While  
  
        Catch ex As Exception  
            Throw New ApplicationException(ex.Message)  
        Finally  
  
            If iStream IsNot Nothing Then  
                //Close the file.  
                iStream.Close()  
                iStream = Nothing  
            End If  
  
            Response.Close()  
        End Try  
    End If  
End Sub  

Edit

<asp:TreeView ID="TreeView1" runat="server" Font-Names="Trebuchet MS" Font-Size="15px" ForeColor="blue" Font-Bold="true" OnSelectedNodeChanged="TreeView1_SelectedNodeChanged">  
<Nodes>  
<asp:TreeNode>  
<asp:TreeNode Text="Stud2" Value="Stud2" Target="_blank">  
</asp:TreeNode>  
</asp:TreeNode>  
</Nodes>  
</asp:TreeView>  
Public Sub TreeView1_SelectedNodeChanged(sender As Object, e As EventArgs)  
        Dim filename = Server.MapPath("Test.pdf")  
        If File.Exists(filename) Then  
            Response.Clear()  
            Using oBinaryReader As BinaryReader = New BinaryReader(File.OpenRead(filename))  
                Response.ContentType = "application/octet-stream"  
                Response.AppendHeader("Content-Disposition", "attachment; filename=" + filename)  
                Response.TransmitFile(filename)  
                Response.End()  
            End Using  
        End If  
    End Sub  

Best regards,
Lan Huang

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Answer 2

I think you used the wrong tag for this post. Is this really an ASP.NET Core question? The code looks like .NET Framework, maybe Web Forms??? If you posted in the wrong subject and this is actually a Web Forms question then try using...

Response.TransmitFile(pathtoyourfile);  

HttpResponse.TransmitFile Method

Your current approach places the entire file in memory which is not a good approach for large files.