When I was asked how to show file extensions in lists of documents on SharePoint sites I thought it would be a simple change to make. I did a quick Google and found several answers; but some of them involved editing core files that instinctively I thought should be left alone. I took a closer look and worked out the steps.

It turns out that you need SharePoint designer, plus you have to convert a web part to XSLT, and then figure out what to change in the rather complex page that is then generated.

A few observations.

First, I am surprised that Microsoft did not build in some easy way of showing the file extensions in a document library, which seems an obvious thing to want to do. There are hundreds of much more obscure things you can easily show, but not this one.

Second, it is nice that Microsoft has made its SharePoint Designer tool free, but I am not sure that the way it is presented is quite right. It is a techie product but I did not find Help particularly helpful. You know the kind of thing; you are in the Formula Editor, you hit F1, and you get a description of the dialog, when what you want of course is a reference to the formulae.

Third, when I did find the documentation I found it obscure. Here’s the reference for the @LinkFileName formula:

Returns a GUID that represents the icon that is used to create a link to a file in a document library, where the file can be edited by using a menu.

Hmm. I am not sure how many fat SharePoint books you need to read to understand why this particular formula is used as it is in SharePoint, or why String(@LinkFileName) returns the file name with its extension.

Fourth, I discovered that SharePoint deliberately hides the file extension. You can show the extension by removing the function that strips it off, in the formula that determines the contents of that cell.

Now I know why SharePoint is such good business for specialists.