将文件从url下载到.Net Core中的本地设备

Question

在.Net 4.0中,我使用WebClient从URL下载文件并将其保存在本地驱动器上.但是我无法在.Net Core中实现相同的功能.

任何人都可以帮我解决这个问题吗？

Answer 1

WebClient不可用.NET Core.(UPDATE:它是从2.0)的使用HttpClient在System.Net.Http因此强制性:

using System.Net.Http;
using System.Threading.Tasks;
...
public static async Task<byte[]> DownloadFile(string url)
{
    using (var client = new HttpClient())
    {

        using (var result = await client.GetAsync(url))
        {
            if (result.IsSuccessStatusCode)
            {
                return await result.Content.ReadAsByteArrayAsync();
            }

        }
    }
    return null;
}

Answer 2

在NetCore 6.0中，您应该使用已过时的HttpClient代替WebClient，并且您在新类中拥有异步方法File。

实现简单如下：

static async Task DownloadFile(string url, string pathToSave, string fileName)
{
    var content = await GetUrlContent(url);
    if (content != null)
    {
        if (!Directory.Exists(pathToSave)) Directory.CreateDirectory(pathToSave);
        await File.WriteAllBytesAsync($"{pathToSave}/{fileName}", content);
    }
}

static async Task<byte[]?> GetUrlContent(string url)
{
    using (var client = new HttpClient())
    using (var result = await client.GetAsync(url))
        return result.IsSuccessStatusCode ? await result.Content.ReadAsByteArrayAsync():null;
}

用法：

await DownloadFile("https://exampl.com/image.jpg", @"c:\DownloadedImages", "image.jpg");

Answer 3

WebClient可从.net core 2.0获得

var wc = new System.Net.WebClient();
wc.DownloadFile( URL, @"c:\temp\myfile.txt");