From url to file

底下的程式碼, 可以將網路上的圖片直接轉成Thumb並儲存在硬碟檔案中.

請注意, 不要使用 BitmapImage bmp=new BitmapImage(new Uri(n, UriKind.RelativeOrAbsolute))); 因這種方法還需等待下載時間完成後才能存檔. 需加入 bmp.DownloadCompleted += new EventHandler(Image_DownloadCompleted);
但因為下一張圖片立即執行, 致使上一張的DownloadCompleted通常不會發生, 非常難控制

private void btn_Click(object sender, RoutedEventArgs e)
{
    new Thread(() => {
        int length;
        byte[] data=new byte[1024];
        WebRequest request;
        WebResonse response;
        Stream webStream;
        for (int i = 0; i < s.Length; i++) 
            { 
                try
                    {
			string url = s[i];
			request = WebRequest.Create(url);
			response = request.GetResponse();
			webStream = response.GetResponseStream();
			memoryStream = new MemoryStream();
			while ((length = webStream.Read(data, 0, data.Length)) > 0)
			{
                            memoryStream.Write(data, 0, length);
			}
			memoryStream.Seek(0, SeekOrigin.Begin);
			bitmap = new BitmapImage();
			bitmap.BeginInit();
			bitmap.CacheOption = BitmapCacheOption.OnLoad;
			bitmap.StreamSource = memoryStream;
			bitmap.DecodePixelWidth = 200;
			bitmap.EndInit();
			bitmap.Freeze();
			encoder = new JpegBitmapEncoder();
			encoder.Frames.Add(BitmapFrame.Create(bitmap));
			using (fileStream = new System.IO.FileStream(string.Format("d:/tmp/t{0}_near.jpg", pcount++), FileMode.Create))
			{
				encoder.Save(fileStream);
			}
		}
		catch (Exception ex)
		{
			Console.WriteLine("無此網址 or 照片");
		}
	}
    }).Start();
}