如何从远程URL获取有效的文件名和扩展名以保存它.

Question

我想从远程网址获得实际的文件扩展名.

有时扩展名不是有效格式.

例如,
我从下面的URL中遇到问题

1) http://tctechcrunch2011.files.wordpress.com/2011/09/media-upload.png?w=266
2) http://0.gravatar.com/avatar/a5a5ed70fa7c651aa5ec9ca8de57a4b8?s=60&d=identicon&r=G

我想从远程网址下载/保存远程图像..

如何从上面的URL获取文件名和扩展名？

谢谢
Abhishek

Answer 1

远程服务器发送Content-Type包含资源的mime类型的标头.例如:

Content-Type: image/png

因此,您可以检查此标头的值,并为您的文件选择适当的扩展名.例如:

WebRequest request = WebRequest.Create("http://0.gravatar.com/avatar/a5a5ed70fa7c651aa5ec9ca8de57a4b8?s=60&d=identicon&r=G");
using (WebResponse response = request.GetResponse())
using (Stream stream = response.GetResponseStream())
{
    string contentType = response.ContentType;
    // TODO: examine the content type and decide how to name your file
    string filename = "test.jpg";

    // Download the file
    using (Stream file = File.OpenWrite(filename))
    {
        // Remark: if the file is very big read it in chunks
        // to avoid loading it into memory
        byte[] buffer = new byte[response.ContentLength];
        stream.Read(buffer, 0, buffer.Length);
        file.Write(buffer, 0, buffer.Length);
    }
}