C# Response如何处理大文件下载

原文链接：https://www.yisu.com/ask/18923534.html

在C#中处理大文件下载通常需要考虑以下几个方面：

1、使用流（Stream）来处理大文件下载，可以有效避免一次性加载整个文件到内存中，节约内存资源。可以使用HttpWebRequest或HttpClient来获取文件的流，然后逐块下载文件内容。

using System;
using System.IO;
using System.Net;
 
public class FileDownloader
{
    public void DownloadFile(string url, string savePath)
    {
        using (var client = new WebClient())
        {
            using (var stream = client.OpenRead(url))
            {
                using (var fileStream = new FileStream(savePath, FileMode.Create))
                {
                    byte[] buffer = new byte[4096];
                    int bytesRead;
                    while ((bytesRead = stream.Read(buffer, 0, buffer.Length)) > 0)
                    {
                        fileStream.Write(buffer, 0, bytesRead);
                    }
                }
            }
        }
    }
}

2、使用异步下载来提高下载性能，可以使用HttpClient的异步方法来下载文件。

using System;
using System.IO;
using System.Net.Http;
using System.Threading.Tasks;
 
public class FileDownloader
{
    public async Task DownloadFileAsync(string url, string savePath)
    {
        using (var client = new HttpClient())
        {
            using (var stream = await client.GetStreamAsync(url))
            {
                using (var fileStream = new FileStream(savePath, FileMode.Create))
                {
                    await stream.CopyToAsync(fileStream);
                }
            }
        }
    }
}

　　3、考虑断点续传功能，可以在下载过程中记录已经下载的文件大小，以便在下载中断后可以继续下载。

public class FileDownloader
{
    public async Task DownloadFileWithResumeAsync(string url, string savePath)
    {
        long fileSize = 0;
        if (File.Exists(savePath))
        {
            fileSize = new FileInfo(savePath).Length;
        }
         
        using (var client = new HttpClient())
        {
            var request = new HttpRequestMessage(HttpMethod.Get, url);
            request.Headers.Range = new System.Net.Http.Headers.RangeHeaderValue(fileSize, null);
            using (var response = await client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead))
            {
                using (var stream = await response.Content.ReadAsStreamAsync())
                {
                    using (var fileStream = new FileStream(savePath, FileMode.Append))
                    {
                        await stream.CopyToAsync(fileStream);
                    }
                }
            }
        }
    }
}