Display actual file size next to a hyperlink of a document or download_问答_开发者

I've always been required show download size next to the file开发者_如何学Python hyperlink. Only the file in question is rebuilt everyday and the file size can change often. So needless to say the size has been wrong for months. I'm not going to update our site daily to display needless info.

instead of

<a href="file.xxx">click here to download (20mb)</a>

I'd prefer

<a href="file.xxx">click here to download [sizeof('file.xxx')]</a>

The best solution would be javascript based or similar.

Since the file is on the server the solution would be best using ASP.NET. This blog post shows how to find the size of a file on the server. You may be able to adapt it to your needs.

javascript isn't really the best language to query the file system. There are ways to do it but they are all very hacky and you should stay away from them.

You can get the file size dynamically using server side code though :

long fileSize = (new FileInfo(@ ".\file")).Length;

So in your markup, you could have something like :

<asp:Hyperlink runat="server" ID="hyperlinkFile" ...>

In your code behind, set it properly :

this.hyperlinkFile.Text = "Click here to download" + fileSize.ToString();

Use XMLHttpRequest to send a HEAD to the file and parse the HTTP Header that you get back, looking for the Content-Length field.

Something like:

var client = new XMLHttpRequest();
client.onreadystatechange = function() {
  if(this.readyState == 2) {
    alert(client.getResponseHeader("Content-Length"));
  }
}
client.open("HEAD", address);
client.send();

More information here:

http://ajaxpatterns.org/XMLHttpRequest_Call

The final solution will be a mix between server code (asp.net) and client code (js). You can build a REST service, that based on the file name or path, returns the size.

You can implement a js function that updates the inner text of every with the result of the REST service call.

Do something like this

<a href="file.xxx">click here to download (<%= C# or VB code for file size %>) </a>

Inside the <%= %> tag you can put C# or VB code to find the file size. The server will evaluate it and then put the result where that tag is.

Just create a column name 'FileSize' in your database and fill it with asp.net after your upload has finished. This makes sure you won't overload your server too much.

[edit]Sorry didnt see your file size changes every day[/edit] In that case you could write a little FileSystem Watcher and let it run in the background on your server or you could just get the filesize by checking the FileSystem info, way easier.

I thought about this more...I read all your answers, then clicked on some links to download various files from other websites. The browser tells me the size after I click 'download' in the dialog box.

I'm going to change the mind set that it is even necessary to include in the link.

Our site has so many pointless...('well other sites have this feature')...and the person I replaced didn't realize or care he that those other sites were built with a CMS that does all that automatically. Example: He was hard coding at the bottom of each page 'last updated: 01/01/1900' every time he saved the document.

edit:
I don't like the way I phrased this answer the other day. I realized that it is unnecessary to include the file size in the hyperlink, when all the major browsers will indicate the file size once you click 'download'. Like in my example above, there are so many instances I can find where the developer or webmaster before me added additional work for themselves by including "features" like filesizes/timestamps/etc... In my opinion adding features like that have/are: