c# - 大文件下载功能失败

Question

嗨，我的下载功能。

protected void downloadFunction(string fileName)
{
    string filePath = @"D:\SoftwareFiles\";
    LogMessageToFile("Download started " + filePath + fileName);
    byte[] array = File.ReadAllBytes(filePath + fileName);
        

    Response.Clear();
    Response.ContentType = "application/x-newton-compatible-pkg";
    Response.AppendHeader("Content-Disposition", 
                          "attachment;filename=" + fileName);

    Response.BinaryWrite(array);
    Response.End();
}

当处理 20、200mb 的文件时没问题。

处理1gb文件时，抛出异常:

Overflow or underflow in the arithmetic operation.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.ArithmeticException: Overflow or underflow in the arithmetic operation.

怎么办？

Answer 1

我的猜测是您在 byte[] 数组 中的内存不足。

您可以尝试将文件分解并分块读取。

我从 Google 搜索中找到了一个代码示例来帮助您入门:

C# file downloader AKA Response.BinaryWrite

using System;
using System.IO;
using System.Web;

public class Download
{
    public static void SmallFile(string filename, string filepath, string contentType)
    {
        try
        {
            FileStream MyFileStream = new FileStream(filepath, FileMode.Open, FileAccess.Read, FileShare.Read);
            long FileSize;
            FileSize = MyFileStream.Length;
            byte[] Buffer = new byte[(int)FileSize];
            MyFileStream.Read(Buffer, 0, (int)MyFileStream.Length);
            MyFileStream.Close();
            HttpContext.Current.Response.ContentType = contentType;
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));
            HttpContext.Current.Response.BinaryWrite(Buffer);             
        }
        catch
        {
            HttpContext.Current.Response.ContentType = "text/html";
            HttpContext.Current.Response.Write("Downloading Error!");
        }
        HttpContext.Current.Response.End();
    }

    public static void LargeFile(string filename, string filepath, string contentType)
    {
        Stream iStream = null;
        // Buffer to read 10K bytes in chunk
        //byte[] buffer = new Byte[10000];
        // Buffer to read 1024K bytes in chunk
        byte[] buffer = new Byte[1048576];

        // Length of the file:
        int length;
        // Total bytes to read:
        long dataToRead;

        try
        {
            // Open the file. 
            iStream = new FileStream(filepath, FileMode.Open, FileAccess.Read, FileShare.Read);

            // Total bytes to read:
            dataToRead = iStream.Length;
            HttpContext.Current.Response.ContentType = contentType;
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));

            // Read the bytes.
            while (dataToRead > 0)
            {
                // Verify that the client is connected.
                if (HttpContext.Current.Response.IsClientConnected)
                {
                    // Read the data in buffer.
                    length = iStream.Read(buffer, 0, 10000);

                    // Write the data to the current output stream.
                    HttpContext.Current.Response.OutputStream.Write(buffer, 0, length);

                    // Flush the data to the HTML output.
                    HttpContext.Current.Response.Flush();

                    buffer = new Byte[10000];
                    dataToRead = dataToRead - length;
                }
                else
                {
                    //prevent infinite loop if user disconnects
                    dataToRead = -1;
                }
            }
        }
        catch (Exception ex)
        {
            // Trap the error, if any.
            //HttpContext.Current.Response.Write("Error : " + ex.Message);
            HttpContext.Current.Response.ContentType = "text/html";
            HttpContext.Current.Response.Write("Error : file not found");                 
        }
        finally
        {
            if (iStream != null)
            {
                //Close the file.
                iStream.Close();
            }
            HttpContext.Current.Response.End();
            HttpContext.Current.Response.Close();             
        }         
    }

    public static void ResumableFile(string filename, string fullpath, string contentType)
    {
        try
        {
            FileStream myFile = new FileStream(fullpath, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
            BinaryReader br = new BinaryReader(myFile);
            try
            {
                HttpContext.Current.Response.AddHeader("Accept-Ranges", "bytes");
                HttpContext.Current.Response.Buffer = false;
                long fileLength = myFile.Length;
                long startBytes = 0;

                //int pack = 10240; //10K bytes
                int pack = 1048576; //1024K bytes

                if (HttpContext.Current.Request.Headers["Range"] != null)
                {
                    HttpContext.Current.Response.StatusCode = 206;
                    string[] range = HttpContext.Current.Request.Headers["Range"].Split(new char[] { '=', '-' });
                    startBytes = Convert.ToInt64(range[1]);
                }
                HttpContext.Current.Response.AddHeader("Content-Length", (fileLength - startBytes).ToString());
                if (startBytes != 0)
                {
                    HttpContext.Current.Response.AddHeader("Content-Range", string.Format(" bytes {0}-{1}/{2}", startBytes, fileLength - 1, fileLength));
                }
                HttpContext.Current.Response.AddHeader("Connection", "Keep-Alive");
                HttpContext.Current.Response.ContentType = contentType;
                HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(filename, System.Text.Encoding.UTF8));

                br.BaseStream.Seek(startBytes, SeekOrigin.Begin);
                int maxCount = (int)Math.Floor((double)((fileLength - startBytes) / pack)) + 1;

                for (int i = 0; i < maxCount; i++)
                {
                    if (HttpContext.Current.Response.IsClientConnected)
                    {
                        HttpContext.Current.Response.BinaryWrite(br.ReadBytes(pack));
                    }
                    else
                    {
                        i = maxCount;
                    }
                }
            }
            catch
            {
                HttpContext.Current.Response.ContentType = "text/html";
                HttpContext.Current.Response.Write("Error : file not found");
            }
            finally
            {
                br.Close();
                myFile.Close();
            }
        }
        catch
        {
            HttpContext.Current.Response.ContentType = "text/html";
            HttpContext.Current.Response.Write("Error : file not found");
        }
    }     
}