# Collection Validity

The Cognex Communication Card API uses the Valid property to indicate whether the configuration of the precision I/O events in a collection are valid (true) or not (false). The property is updated automatically as events are added to the collection.

The precision I/O event collection cannot function while its Valid property is false, which can happen if you do any of the following:

- Set LineBank to a value not supported by the Cognex Communication Card.
- Set LineNumber to a value not supported by the Cognex Communication Card.
- Configure two or more events to share the same LineBank, LineNumber and LineTransition.
- Set OutputLineNumber to a value greater than the number of lines supported by the current bank.
- Configure two or more events to share the same OutputLineBank, OutputLineNumber, and OutputLineValue.
- Set DelayValue to a negative value when DelayType is set to Time (2).

Cognex strongly recommends your application check the status of the Valid property as it launches, and use the ValidationErrorMsg property as necessary to view the error messages that describe issues with the events collection.