C#异步下载文件--基于http请求

1.废话不多说，直接上代码：

using System;
using System.IO;
using System.Net;

namespace AsyncProgram
{
    class Program
    {
        static void Main(string[] args)
        {
            do
            {
                Console.WriteLine("请输入要下载的文件地址,输入quit退出！");
                string url = Console.ReadLine();

                if (url == "quit") break;

                if (!url.StartsWith("http://"))
                {
                    Console.WriteLine("只能支持http://开头的下载地址！");
                    continue;
                }

                string []strs = url.Split(new char[] { '/'},StringSplitOptions.RemoveEmptyEntries);
                string fileName = strs[strs.Length-1];

                WebRequest webRequest = WebRequest.Create(url);

                webRequest.BeginGetResponse(DownloadFinished, new Mystate { FileName = fileName, WebRequestObject = webRequest });

                Console.WriteLine($"已在后台自动下载文件：{fileName}
");

            } while (true);

            Console.WriteLine("正在下载文件...");

            Console.WriteLine("关闭次窗口前，请确保文件已全部下载完成！按任意键关闭窗口...");

            Console.ReadKey();

        }

        static void DownloadFinished(IAsyncResult ar)
        {
            try
            {
                Mystate state = ar.AsyncState as Mystate;
                WebResponse response = state.WebRequestObject.EndGetResponse(ar);

                Stream inStream = response.GetResponseStream();
                byte[] buffer = new byte[1024*1024];
                Stream outStream = System.IO.File.Create(System.AppDomain.CurrentDomain.BaseDirectory + state.FileName);
                try
                {
                    int l;
                    do
                    {
                        l = inStream.Read(buffer, 0, buffer.Length);
                        if (l > 0) outStream.Write(buffer, 0, l);
                    } while (l > 0);
                }
                finally
                {
                    if (outStream != null) outStream.Close();
                    if (inStream != null) inStream.Close();
                }

            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }

    public class Mystate
    {
        public string FileName { get; set; }
        public WebRequest WebRequestObject { get; set; }
    }
}