C#实现网络下载文件

    public static bool DownLoadFiles(string uri, string filefullpath, int size = 1024)
        {
            try
            {
                if (File.Exists(filefullpath))
                {
                    try
                    {
                        File.Delete(filefullpath);
                    }
                    catch (Exception ex)
                    {
                        return false;
                    }
                }
                string fileDirectory = System.IO.Path.GetDirectoryName(filefullpath);
                if (!Directory.Exists(fileDirectory))
                {
                    Directory.CreateDirectory(fileDirectory);
                }
                FileStream fs = new FileStream(filefullpath, FileMode.Create);
                byte[] buffer = new byte[size];
                HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(uri);
                request.Timeout = 10000;
                request.AddRange((int)fs.Length);

                Stream ns = request.GetResponse().GetResponseStream();

                long contentLength = request.GetResponse().ContentLength;

                int length = ns.Read(buffer, 0, buffer.Length);

                while (length > 0)
                {
                    fs.Write(buffer, 0, length);

                    buffer = new byte[size];

                    length = ns.Read(buffer, 0, buffer.Length);
                }
                fs.Close();
                return true;
            }
            catch (Exception ex)
            {
                return false;
            }
        }