Event Example

This article includes a simple code example to explain how to use Business Central events. The example uses an event to verify a customer's address. When a user changes the address of a customer on the page 21 Customer Card, an event is used to check that the address doesn't include a plus sign (+). If it does, a message is displayed in the client. In this example, you'll add code that:

• Publishes an event that is raised when the Address field on Customer Card is changed.
• Raises the event from the Customer Card page
• Subscribes to the event to check the address value and return a message to the user if it contains a plus sign.

// The following code creates codeunit that publishes the `OnAddressLineChanged` event.

codeunit 50100 MyPublishers
{
    [IntegrationEvent(false, false)]
    procedure OnAddressLineChanged(line: Text[100])
    begin
    end;
}

// The following code extends the Customer Card page to raise the `OnAddressLineChanged` event
// when the Address field is changed.
pageextension 50100 MyCustomerExt extends "Customer Card"
{
    layout
    {
        modify(Address)
        {
            trigger OnBeforeValidate();
            var
                Publisher: Codeunit MyPublishers;
            begin
                Publisher.OnAddressLineChanged(Rec.Address);
            end;
        }
    }
}

// The following code creates an event subscriber codeunit.
// It declares the `CheckAddressLine` event subscriber that listens for OnAddressLineChanged event.
// The event subscriber displays a message in the client when '+' is used in the **Address** field.

codeunit 50101 MySubscribers
{
    //Set the event subscribers to bind automatically to the event
    EventSubscriberInstance = StaticAutomatic;

    [EventSubscriber(ObjectType::Codeunit, Codeunit::"MyPublishers", 'OnAddressLineChanged', '', true, true)]
    procedure CheckAddressLine(line: Text[100])
    begin
        if (STRPOS(line, '+') > 0) then begin
            MESSAGE('Can''t use a plus sign (+) in the address [' + line + ']');
        end;
    end;
}

Tip

This example binds the event subscriber automatically to the event. You can also bind the event subscriber manually, by setting the EventSubscriberInstance property. For more information, including an example, see EventSubscriberInstance property.

See Also

Publishing Events
Raising Events
Subscribing to Events
Events Dynamics 365