|Download Help (Windows Only)|
Registers a VI to be called when an event occurs. You use this function to register and handle .NET and ActiveX events. LabVIEW uses the type of the input reference wired to each item to determine the events for which you can register. You can resize the function to register multiple event callbacks at once for the same .NET or ActiveX object or for a different object. Details Examples
|event callback ref accepts a reference to an existing event callback registration.|
|error in describes error conditions that occur before this VI or function runs.
The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.
|event source ref accepts a .NET object or an ActiveX automation reference. Click the down arrow next to this input and select the type of event you want to generate, such as Mouse Down or Double Click. References must be to local objects. You cannot wire a reference to a remote object.|
|vi reference is a strict VI reference to the callback VI. vi reference must match exactly the data from the registered event and the callback VI must be reentrant.|
|user parameter contains data that you want to pass to the callback VI when the .NET or ActiveX object generates the event. For example, you can wire a string that includes a text message to the user parameter input to tell a user for which control the event occurred. If you want to use this parameter, you must wire it before you create the callback VI. You can wire any LabVIEW data type, including a cluster, to this parameter.|
|event callback ref out returns a reference to a new or existing callback registration.|
|error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces.
Right-click the error out front panel indicator and select Explain Error from the shortcut menu for more information about the error.
Use this function to register .NET and ActiveX events only. To unregister an event for .NET or ActiveX, wire the event callback ref out output to the Unregister For Events function.
Refer to the following VIs for examples of using the Register Event Callback function: