Getting a header/filesize in .NET

问题

I have a link to two files. They may be the same file, but they may not be the same URL. I want to figure out if they are the same by checking the content-length before doing a full download. What's the best way to do this?

Currently I am using webbrowser control to load the page and extract data and then using WebClient.Download to get the file. Is there a way I can use WebClient to check the filesize before downloading the entire file?

回答1:

I found an excellent article, Get file length over HTTP before you download it, which provides a way that works very well for me:

    static public long GetFileSize(string url)
    {
        using (WebClient obj = new WebClient())
        using (Stream s = obj.OpenRead(url))
            return long.Parse(obj.ResponseHeaders["Content-Length"].ToString());
    }

回答2:

Equality of lengths does not mean that files are identical. However, if you're sure that this is enough to assert equality, you can issue a HttpWebRequest with Method set to HEAD: this will only download file headers, including content-length.

来源：https://stackoverflow.com/questions/1176928/getting-a-header-filesize-in-net