Binding Event Subscribers

Skill: AL Event Binding

Validation Gates

1. After Step 1: Manual codeunit compiles, subscribers don't fire without binding
2. After Step 2: BindSubscription activates subscriber, events fire correctly
3. Final: UnbindSubscription deactivates, no events fire after unbind

Note: Default to StaticAutomatic. Use Manual only for conditional/performance scenarios. Binding is session-specific.

Procedure

Step 1: Create Manual Subscriber Codeunit

codeunit  "  Subscribers"
{
    EventSubscriberInstance = Manual;

    [EventSubscriber(ObjectType::Table, Database::, 'OnAfterValidateEvent', '', false, false)]
    local procedure OnValidate(var Rec: Record )
    begin
        // Your validation logic here
        if StrLen(Rec.)  must be at least 3 characters');
    end;
}

Step 2: Bind in Context (Page/Codeunit)

pageextension  "  Card Ext" extends ""
{
    var
        EntitySubscribers: Codeunit "  Subscribers";

    trigger OnOpenPage()
    begin
        BindSubscription(EntitySubscribers);
    end;

    trigger OnClosePage()
    begin
        UnbindSubscription(EntitySubscribers);
    end;
}

Common Patterns

Conditional via Setup

procedure ProcessDocument(var SourceRecord: Record )
var
    AdvancedValidation: Codeunit " Advanced Validation";
    Setup: Record " Setup";
begin
    if Setup.Get() and Setup."Enable Advanced Validation" then
        BindSubscription(AdvancedValidation);

    Codeunit.Run(Codeunit::, SourceRecord);
    // Auto-unbinds when procedure ends
end;

Batch Job Optimization

UI subscribers bound only in pages, not in job queue codeunits:

• Page: OnOpenPage → BindSubscription(UINotifications)
• Job Queue: No binding → no UI overhead

Important Notes

Binding behavior:

• Session-specific (Session A binding doesn't affect Session B)
• Auto-dissolves when codeunit instance goes out of scope
• Cannot call Bind/Unbind on StaticAutomatic codeunits (runtime error)

Stale metadata: Recompiling bound codeunit shows error "subscriber is stale" - only during development, not production.

⚠️ Do NOT use Manual for critical business logic that must never be missed.

External Documentation

• EventSubscriberInstance Property
• BindSubscription Method

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: emgreppi
• Source: emgreppi/Business-Central-AI-Skill
• License: MIT

Install and usage instructions live in the source repository linked above.