Primary Display Field in Autocomplete controls

[SharePoint.Gurus]

What do you need to do to make a field available as the Primary Display Field in an Autocomplete control?

The table in the Autocomplete control's Row Source has a number of short text columns, but only one of them is available in the drop down list for Primary Display Field.

 

[SharePoint.Gurus]

OK - I figured it out. The Primary Display Column is based on the display field you select when you set up the lookup column. It seems strange that you are given a drop down to choose the primary display column, I guess sometimes you might want to set it to "not specified" so that you show the underlying ID.

So I modified the lookup properties in the table and I was then able to set the Primary Display Column to the value I wanted.