Is there any way to get the file extension from a URL

Question

I want to know that for make sure that the file that will be download from my script will have the extension I want.

The file will not be at URLs like:

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Answer 1

If you just want to get the .jpg part of http://example.com/file.jpg then just use Path.GetExtension as heringer suggests.

// The following evaluates to ".jpg"
Path.GetExtension("http://example.com/file.jpg")

If the download link is something like http://example.com/this_url_will_download_a_file then the filename will be contained as part of the Content-Disposition, a HTTP header that is used to suggest a filename for browsers that display a "save file" dialog. If you want to get this filename then you can use the technique suggested by Get filename without Content-Disposition to initiate the download and get the HTTP headers, but cancel the download without actually downloading any of the file

HttpWebResponse res = (HttpWebResponse)request.GetResponse();
using (Stream rstream = res.GetResponseStream())
{
    string fileName = res.Headers["Content-Disposition"] != null ?
        res.Headers["Content-Disposition"].Replace("attachment; filename=", "").Replace("\"", "") :
        res.Headers["Location"] != null ? Path.GetFileName(res.Headers["Location"]) : 
        Path.GetFileName(url).Contains('?') || Path.GetFileName(url).Contains('=') ?
        Path.GetFileName(res.ResponseUri.ToString()) : defaultFileName;
}
res.Close();