ASP.NET Resource Reference Best Practices

Question

I'm relatively new to ASP.NET and was wondering if anyone could shed some light on when I should use relative references (e.g. ../images/banner_tinga.jpg) versus the tilde (e.g. ~/images/banner_tinga.jpg). Depending on the situation you can accomplish the same goal using either. What are the pros and cons of each mechanism? One argument for the relative reference seems to be Visual Studio's design time dislike for resources referenced by the tilde. Whenever I reference a css file that why it indicates it can not be found.

Regards, javacavaj

Answer 1

Personally I only use relative references now and avoid the tilde. It may lead to problems further down the line. Although I can't show any reference material connected to it, I remember hearing/reading somewhere that tilde references have been deprecated

Answer 2

Hello,

The tilde will work only with controls that have runat="server" attribute, and will not work with standard HTML controls. So there's really no universal choice. If you wish to use use tilde with HTML controls you'll have to mark them runat="server", like this

<img src="~/images/myimage.png" runat="server">

But it doesn't seem like a good practice cause it will be added to the viewstate. But then, you can also do this

<img src="~/images/myimage.png" runat="server" EnableViewState="False">

So then the choice becomes truly universal.

Now answering your original question:

I think it's better to use the '~' tilde, because it gives you a point of reference -- the root of your website. The relative path scheme '../' will fail if you change the folder of the webpage and take it to a different level (higher or lower in the hierarchy)

Hope this helped.

To get to your CSS file, do this

<link href="<%= VirtualPathUtility.ToAbsolute("~/css/style.css/") %>" type="text/css">

Answer 3

Hmmm...I disagree with @StevenMcD completely. The tilde always references the root of the web application that you're developing, whereas the relative path notation is based upon your current location within the web application. I think in the long run, if you reorganize or restructure the file locations of the web pages, the tilde notation will make it much easier for you to refactor since you always know that the base path (~) is referring to the root of the web application. You cannot be assured of that if using "../" notation.

One other note...the tilde (~) notation is very handy when using user controls and masterpages in ASP.NET. When you drop in a user control onto a webform, that webform can be nested in any part of your application's file structure. Relative paths simply aren't guaranteed to work in that scenarion. By using the tilde notation, all paths can be written in code and will work because they're based on the root of the web application. Hope this helps.

By the way, the use of the ~ is not deprecated in any way in ASP.NET.

UPDATE: As Cyril mentioned, the ~ is only available to you when using ASP.NET controls. Pure HTML elements won't work with it.