C# 下载文件

法一：

WebClient wc = new WebClient();
                wc.DownloadFile(fileurl.ToString(), @"D:/" + filename);

 

法二：

try
            {
                HttpWebRequest myWebRequest = (HttpWebRequest)WebRequest.Create(url);
                HttpWebResponse myWebResponse = (HttpWebResponse)myWebRequest.GetResponse();
                Stream readStream = myWebResponse.GetResponseStream();

                System.Drawing.Image image = System.Drawing.Image.FromStream(readStream);

                // TODO 应该新建对象
                //System.Drawing.Image tif = image;
                
                // 获取图片页数
                Guid guid = (Guid)image.FrameDimensionsList.GetValue(0);
                FrameDimension dimension = new FrameDimension(guid);
                int pages = image.GetFrameCount(dimension);

                // 保存图片类型 -> tif
                ImageCodecInfo codeInfo = GetEncoder(ImageFormat.Tiff);

                // 保存参数
                System.Drawing.Imaging.Encoder saveEncoder = System.Drawing.Imaging.Encoder.SaveFlag;

                EncoderParameters parameters = new EncoderParameters(1);
                
                // 参数-指定为多页
                parameters.Param[0] = new EncoderParameter(saveEncoder, Convert.ToInt32(EncoderValue.MultiFrame));

                // 保存第一页
                image.Save(@"C:/1.tif", codeInfo, parameters);

                // 参数-添加页面
                parameters.Param[0] = new EncoderParameter(saveEncoder, Convert.ToInt32(EncoderValue.FrameDimensionPage));

                // 保存后续页面
                for (int i = 1; i < pages; i++)
                {
                    image.SelectActiveFrame(dimension, i);
                    image.SaveAdd(image, parameters);
                }

                // 所有页面保存完毕
                parameters.Param[0] =new EncoderParameter(saveEncoder, Convert.ToInt32(EncoderValue.Flush));

                image.SaveAdd(parameters);

                readStream.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

 

private ImageCodecInfo GetEncoder(ImageFormat format)
        {
            ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();

            foreach (ImageCodecInfo codec in codecs)
            {
                if (codec.FormatID == format.Guid)
                {
                    return codec;
                }
            }
            return null;
        }