I'm creating a simple little search page, and I start by slapping my
trusty DataView control into place. Add some form fields, create Parameters
to correspond to Controls -- wondering why SPD seems to forget which control
goes to which parameter -- and create some Filter criteria based on the
Parameters. So far, so good.

But wait.

When one of the form fields is blank, my filter criteria (of the form "Field
X Contains Parameter A") will return no results. Any idea why this is
happening, or how to get around it? I seem to recall being able to manually
edit the XPath query and add an "or Field X is empty" criterion to get
around this, but that was months ago and I can't seem to do that this time.

Any thoughts?