Raising Events
After an event has been published by an event publisher method, you can modify the application to raise the event where it is needed. Subscribers of an event will not react on the event until it is raised in the application.
To raise an event, you add logic in AL code of the application to call the event publisher method that declares the event. The procedure for calling the event publisher method is the same as calling any other method in AL.
When the code that calls the event publisher method is run, all event subscriber methods that subscribe to the event are run. If there are multiple subscribers, the subscriber methods are run one at a time in no particular order. You cannot specify the order in which the subscriber methods are called.
If there are no subscribers to the published event, then the line of code that calls the event publisher method is ignored and not executed.
Snippet support
Typing the shortcut teventsub will create the basic event subscriber syntax when using the AL Language extension for Microsoft Dynamics 365 Business Central in Visual Studio Code.
Tip
Typing the keyboard shortcut Ctrl+Space displays IntelliSense to help you fill in the attribute arguments and to discover which events are available to use.
Example
This example uses a page extension object 50100 MyCustomerExt to modify the page 21 Customer Card so that an event is raised when a user changes the Address field. This example assumes that the event has already been published by the event publisher method OnAddressLineChanged in a separate codeunit called 50100 MyPublishers.
Note
This example is part of a larger, simple scenario where when users change the address of a customer on the page 21 Customer Card, you want to check that the address does not include a plus sign (+). If it does, you want to return a message to the user. For a description of this scenario and all the code involved, see Event Example.
In the code that follows, the page extension object modifies the OnBeforeValidate trigger of the Customer Card page to raise the event OnAddressLineChanged which includes the new value of the Address field.
pageextension 50100 MyCustomerExt extends "Customer Card"
{
layout
{
modify(Address)
{
trigger OnBeforeValidate();
var
Publisher: Codeunit MyPublishers;
begin
Publisher.OnAddressLineChanged(Rec.Address);
end;
}
}
}
To learn about how the event used in this example is published, see Publishing Events Example.
The next step would be to subscribe to the event to handle to condition. To see an example of how to subscribe to this event, see Subscribing to Events Example.