public void HttpDownload(string url, string path, ResourceType type)

        {

            using (var client = new WebClient())

            {

                client.Headers.Add("User-Agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

                client.Headers.Add("Content-Type", "application/x-www-form-urlencoded");

                var stream = client.OpenRead(url);

                if (type == ResourceType.Document)

                {

                    var header = client.ResponseHeaders["Content-Disposition"];

                    var subStr = header.Split('=');

                    var fileName = System.Web.HttpUtility.UrlDecode(subStr[1]);

                    path = GetFileValidation(path, fileName, out fileName);

                }

                FileStream writeStream = new FileStream(path, FileMode.OpenOrCreate, FileAccess.Write);

                ReadWriteStream(stream, writeStream);

            }

        }

private void ReadWriteStream(Stream readStream, Stream writeStream)

        {

            int Length = 256;

            Byte[] buffer = new Byte[Length];

            int bytesRead = readStream.Read(buffer, 0, Length);

            // write the required bytes

            while (bytesRead > 0)

            {

                writeStream.Write(buffer, 0, bytesRead);

                bytesRead = readStream.Read(buffer, 0, Length);

            }

            readStream.Close();

            writeStream.Close();

        }

//验证文件是否存在

 public string GetFileValidation(string path, string oldTitle, out string newTitle)

        {

            string newPath = System.IO.Path.Combine(path, oldTitle.Replace("\"", ""));

            string title1 = oldTitle;

            if (File.Exists(newPath))

            {

                for (int i = 1; i < int.MaxValue; i++)

                {

                    newPath = System.IO.Path.Combine(path, oldTitle.Split('.')[0] + "(" + i + ")" + "." + oldTitle.Split('.')[1]);

                    if (!File.Exists(newPath))

                    {

                        title1 = oldTitle.Split('.')[0] + "(" + i + ")" + "." + oldTitle.Split('.')[1];

                        break;

                    }

                    else

                    {

                        continue;

                    }

                }

            }

            newTitle = title1;

            return newPath;

        }