> For the complete documentation index, see [llms.txt](https://docs.umbraco.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.umbraco.com/umbraco-ui-builder/advanced/events.md). # Events Configuring event handlers in Umbraco UI Builder. Umbraco UI Builder triggers different notification events during operation, allowing customization of default behavior. ## Registering Event Handlers Umbraco UI Builder follows the [Umbraco Notification mechanism](https://docs.umbraco.com/umbraco-cms/develop-with-umbraco/application-code/backend-and-custom-logic/subscribing-to-notifications) for event registration. Define a notification event handler for the target event: ```csharp public class MyEntitySavingEventHandler : INotificationHandler { public void Handle(EntitySavingNotification notification) { // Handle the event here } } ``` Register the event handler in `Program.cs`: ```csharp builder.CreateUmbracoBuilder() .AddBackOffice() .AddWebsite() .AddDeliveryApi() .AddComposers() .AddNotificationHandler() .Build(); ``` ## Repository Events ### Using the `EntitySavingNotification()` Triggers when `Save` is called before persisting the entity. The notification contains an `Entity` property with `Before` and `After` values, providing access to the previous and updated entities. Modify the `After` entity to persist changes. If the `Cancel` property of the notification is set to `true` then the save operation will be canceled and no changes will be saved. #### Example ```csharp public class MyEntitySavingEventHandler : INotificationHandler { public void Handle(EntitySavingNotification notification) { var person = notification.Entity.After as Person; if (person != null){ ... } } } ``` ### Using the `EntitySavedNotification()` Triggers when the repository `Save` method is called and after the entity has been persisted. The notification contains an `Entity` property with `Before` and `After` inner properties. These properties provide access to a copy of the previously persisted entity (or null if a new entity) and the updated entity that´s saved. #### Example ```csharp public class MyEntitySavedEventHandler : INotificationHandler { public void Handle(EntitySavedNotification notification) { var person = notification.Entity.After as Person; if (person != null){ ... } } } ``` ### Using the `EntityDeletingNotification()` Triggers when the repository `Delete` method is called and **before** the entity is deleted. The notification contains an `Entity` property providing access to a copy of the entity about to be deleted. If the `Cancel` property of notification is set to `true` then the delete operation will be cancelled and entity won't be deleted. #### Example ```csharp public class MyEntityDeletingEventHandler : INotificationHandler { public void Handle(EntityDeletingNotification notification) { var person = notification.Entity.After as Person; if (person != null){ ... } } } ``` ### Using the `EntityDeletedNotification()` Triggers when the repository `Delete` method is called and **after** the entity has been deleted. The notification contains an `Entity` property providing access to a copy of the entity that´s deleted. #### Example ```csharp public class MyEntityDeletedEventHandler : INotificationHandler { public void Handle(EntityDeletedNotification notification) { var person = notification.Entity.After as Person; if (person != null){ ... } } } ``` ### Using the `SqlQueryBuildingNotification()` Triggers when the repository is **preparing** a SQL query. The notification contains the collection alias + type, the NPoco `Sql` object, and the where clause/order by clauses. These will be used to generate the SQL query. #### Example ```csharp public class MySqlQueryBuildingEventHandler : INotificationHandler { public void Handle(SqlQueryBuildingNotification notification) { notification.Sql = notification.Sql.Append("WHERE MyId = @0", 1); } } ``` ### Using the `SqlQueryBuiltNotification()` Triggers when the repository has **repaired** a SQL query. The notification contains the collection alias + type, the NPoco `Sql` object and the where clause/order by clauses that was used to generate the SQL query. #### Example ```csharp public class MySqlQueryBuiltEventHandler : INotificationHandler { public void Handle(SqlQueryBuiltNotification notification) { notification.Sql = notification.Sql.Append("WHERE MyId = @0", 1); } } ``` ## Repository Events Validation From version `15.1.0`, complex server-side validation can be added to a collection using the `CancelOperation` method of the notification. ### Example ```csharp public class MyEntitySavingEventHandler : INotificationHandler { public void Handle(EntitySavingNotification notification) { var person = notification.Entity.After as Person; if (person != null && person.Age < 18) { notification.CancelOperation(new EventMessage("ValidationError", "Custom validation error message raised from the notification handler")); } } } ``` --- # Agent Instructions This documentation is published with GitBook. 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