从.NET / C＃网站下载图像

无需涉及任何图像类，您可以简单地调用

WebClient.DownloadFile

string localFilename = @"c:localpathtofile.jpg";using(WebClient client = new WebClient()){    client.DownloadFile("http://www.example.com/image.jpg", localFilename);}

更新
由于您将要检查文件是否存在并下载文件（如果存在），因此最好在同一请求中执行此操作。所以这是一个可以做到的方法：

private static void DownloadRemoteImageFile(string uri, string fileName){    HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);    HttpWebResponse response = (HttpWebResponse)request.GetResponse();    // Check that the remote file was found. The ContentType    // check is performed since a request for a non-existent    // image file might be redirected to a 404-page, which would    // yield the StatusCode "OK", even though the image was not    // found.    if ((response.StatusCode == HttpStatusCode.OK ||         response.StatusCode == HttpStatusCode.Moved ||         response.StatusCode == HttpStatusCode.Redirect) &&        response.ContentType.StartsWith("image",StringComparison.OrdinalIgnoreCase))    {        // if the remote file was found, download oit        using (Stream inputStream = response.GetResponseStream())        using (Stream outputStream = File.OpenWrite(fileName))        { byte[] buffer = new byte[4096]; int bytesRead; do {     bytesRead = inputStream.Read(buffer, 0, buffer.Length);     outputStream.Write(buffer, 0, bytesRead); } while (bytesRead != 0);        }    }}

简言之，它使该文件，验证该响应代码是中的一个的请求

OK

Moved

Redirect

ContentType