ScanEventArgs Hold

Type: Boolean

Read/write property

Implements a holding pattern that allows end users access to your solution’s user interface while your solution is handling a scanning event on the same thread (typically the main thread of the solution process).

It is initialized to “false” at each event. Set Hold to “true” and also retain a reference to the event context (ScanEventArgs). When the event handler returns control back to Link, Link waits indefinitely for a response from your solution, logically extending the event. The solution’s entire UI is available to your end user and the event context is available to your solution. When ready, simply set Hold to “false” and clear your reference to ScanEventArgs. Link then continues execution.

Link events are “thread modal” much like a message box. While on one hand a message box interacts directly with the end user, an event on the other hand is handled in code unbeknownst to the user. This poses a potential problem.

While the event handler is running a lengthy operation, the UI becomes sluggish or unresponsive and the user thinks the application has hung. You can choose to perform the long running operation on another thread as long as it does not require access to the UI or to Link. If you exit the event handler, the event has come and gone and you cannot respond to Link. What you really want is for Link to “go away for a while without losing the semantics of the event” while you deal with your operation.