Show/hide expression
Description
Specify the show/hide expression for the field.
Discussion
The show/hide expression can refer to session variables (but NOT to fields in the current row). Data for the field is retrieved from the server if the expression is true. If the expression is false, or invalid (perhaps because a referenced session variable has not yet been defined), the field is not shown. Example expressions:
session.var1="alpha"
Using Server-side Show/Hide Expressions with Freeform Layouts
The Show/hide expression property only applies to fields used in a Column List layout. It does not apply in a Freeform layout. Furthermore, this setting only controls whether a particular column in the List layout should be shown -- it does not affect data sent from the server to the browser. (So, for example, if you have set a Show/hide expression on (say) the 'salary' column, the 'salary' column will be hidden in the List, but the List data that is sent from the server to the browser will still include the salary data).
If you want to apply server-side show/hide expressions to one or more fields in a List with a freeform layout, you must apply these settings to the SQL Query on the Data Source tab. The advantage of doing this is that the show/hide expression will be applied at the query level (this restricts access to the data by excluding it from the SQL Query, meaning it is never downloaded to the user's device).
If the List is based on a SQL query, uses a freeform layout, and you have defined sever-side Show/hide expressions for any field in the List data source, Alpha Anywhere will ask if you want to copy your server-side Show/hide expression settings to the Data Source tab when the List Builder is closed.