c#下载网页图片

///
       /// 

       /// 下载网页图片
       /// 
       /// 下载路径
       /// 目标路径
       /// 
       public BitmapImage DownLoadImage(string url, string desPath)
       {   
           WebClient mywebclient = new WebClient();
           mywebclient.DownloadFile(url, desPath);
          BitmapImage image= AddImage2Show(desPath);
          return image;
       }
       /// 

       /// string转换成BitmapImage
       /// 
       /// 
       /// 
       public BitmapImage AddImage2Show(string uri)
       {
           uri = Path.GetFullPath(uri);
           if (!File.Exists(uri))
           {
               return null;
           }
           BitmapImage bitmap = new BitmapImage();
           bitmap.BeginInit();
           bitmap.CacheOption = BitmapCacheOption.OnLoad;//将图片缓存到内存中
           bitmap.UriSource = new System.Uri(uri);
           bitmap.EndInit();
           return bitmap;
       }