试试这个:

private void downloadFile(string url)
{
     string file = System.IO.Path.GetFileName(url);
     WebClient cln = new WebClient();
     cln.DownloadFile(url, file);
}

using System.Net;

WebClient webClient = new WebClient();
webClient.DownloadFile("http://mysite.com/myfile.txt", @"c:\myfile.txt");

这是我的解决方案，效果很好:

public static void DownloadFile(string url, string pathToSaveFile)
        {
            ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
            // or: ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;

            using (WebDownload client = new WebDownload())
            {
                client.Headers["User-Agent"] = "User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36";
                client.DownloadFile(new Uri(url), pathToSaveFile);
            }
        }
    
    public class WebDownload : WebClient
        {
            protected override WebRequest GetWebRequest(Uri address)
            {
                HttpWebRequest request = (HttpWebRequest)base.GetWebRequest(address);
                if (request != null)
                {
                    request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
                }
                return request;
            }
        }

using (var client = new WebClient())
{
    client.DownloadFile("http://example.com/file/song/a.mpeg", "a.mpeg");
}

WebRequest, WebClient和ServicePoint在。net 6(源代码- 2021年11月)中已经过时。

使用System.Net.Http.HttpClient类代替:

using (var client = new HttpClient())
{
    using (var s = client.GetStreamAsync("https://via.placeholder.com/150"))
    {
        using (var fs = new FileStream("localfile.jpg", FileMode.OpenOrCreate))
        {
            s.Result.CopyTo(fs);
        }
    }
}

相同代码的异步版本:

using var client = new HttpClient();
using var s = await client.GetStreamAsync("https://via.placeholder.com/150");
using var fs = new FileStream("localfile.jpg", FileMode.OpenOrCreate);
await s.CopyToAsync(fs);

在.NET Core MVC中，你有时可以简单地这样做:

public async Task<ActionResult> DownloadUrl(string url) {
    return Redirect(url);
}

这可能假设您正在尝试下载的MIME类型被浏览器设置为可下载(例如.mp4)，因此它不会尝试重定向到网页。