Filtering rows in SharePoint Designer not working

I had an issue with SharePoint Designer which left me quite frustrated yesterday.  Today, a colleague mentioned something from his experience which fixed the problem, and made me hate SharePoint Designer even more.

I needed to create a document library view that used a query string as a parameter.  Having done this multiple times, I didn't expect any issues.  However, in this instance, the filter did not work.  It simply showed no items (even though I could clearly see the item I wanted to filter in SharePoint proper, and even filter the column in the usual way in the web browser).

To test, I created a new document library, new view and new filter - this worked perfectly.  After spending a few hours trying to figure this out yesterday, I asked my office buddy to look over my shoulder and see if I'm doing something wrong.

He mentioned that, from his experience, if you click in the column name in SharePoint Designer and assign a Filter from there, it never works.  But if you click on the actual document library content (in SharePoint Designer) and click Filter, it does work.

Seemed too simple to be the issue, but sure enough, that's exactly what it was.

So, if you're trying to filter a list or library in SharePoint Designer, DON'T click on the column header to set up a Filter (even though it gives you the option to do so).  Click on an item row instead.