4.8 Other Events

WebForms Core provides several additional event methods for controlling browser event behavior, triggering existing events, configuring Master Pages, and adding confirmation dialogs to existing events.

These methods do not represent a separate communication protocol such as HTTP, SSE, WebSocket, or Front Events. Instead, they provide additional control over how events are triggered and handled by WebFormsJS.

4.8.1 TriggerEvent

The TriggerEvent method programmatically fires a specified event on a target element. The element is identified through an InputPlace, which acts as a reference to the element you want to trigger the event on. This allows you to simulate user interactions — such as clicks or key presses — without any actual user input.

public void TriggerEvent(string InputPlace, string HtmlEventListener, string ConstructorName = null)

The HtmlEventListener parameter specifies the event to trigger. An optional ConstructorName can be used when the event requires a specific event constructor.

form.TriggerEvent("Button1", HtmlEventListener.Click);

An event constructor can also be specified:

form.TriggerEvent("Button1", HtmlEventListener.Click, "mouseevent");

The available constructor categories include mouse events, keyboard events, UI events, focus events, input events, and general events.

Note: TriggerEvent utilizes the HtmlEventListener event definition, even for direct events that do not involve a listener. Therefore, the HtmlEventListener class must be used for both direct events and listener-based events. Please note that the HtmlEvent class and strings prefixed with "on"—such as "onclick"—should not be used.

4.8.2 Prevent Default Event

The SetPreventDefaultEvent method prevents the browser's default action for an assigned HTML event.

public void SetPreventDefaultEvent(string InputPlace, string HtmlEvent)

For example, the default action of a link can be prevented for its click event:

form.SetPreventDefaultEvent("MyLink", HtmlEvent.OnClick);

The EventListener form is provided by SetPreventDefaultEventListener:

public void SetPreventDefaultEventListener(string InputPlace, string HtmlEventListener) form.SetPreventDefaultEventListener("MyLink", HtmlEventListener.Click);

The two methods allow the same behavior to be defined using either the HTML event or EventListener representation.

Method	Event definition
SetPreventDefaultEvent	HtmlEvent
SetPreventDefaultEventListener	HtmlEventListener

4.8.3 Remove Prevent Default Event

An assigned prevent-default behavior can be removed with RemovePreventDefaultEvent or RemovePreventDefaultEventListener.

public void RemovePreventDefaultEvent(string InputPlace, string HtmlEvent) public void RemovePreventDefaultEventListener(string InputPlace, string HtmlEventListener)

For example:

form.RemovePreventDefaultEvent("MyLink", HtmlEvent.OnClick); form.RemovePreventDefaultEventListener("MyLink", HtmlEventListener.Click);

4.8.4 Stop Propagation Event

The SetStopPropagationEvent method stops propagation of the specified event from the selected element.

public void SetStopPropagationEvent(string InputPlace, string HtmlEvent)

For example:

form.SetStopPropagationEvent("Button1", HtmlEvent.OnClick);

The EventListener form is provided by SetStopPropagationEventListener:

public void SetStopPropagationEventListener(string InputPlace, string HtmlEventListener) form.SetStopPropagationEventListener("Button1", HtmlEventListener.Click);

This allows event propagation behavior to be controlled without writing a JavaScript event handler manually.

4.8.5 Remove Stop Propagation Event

Stop-propagation behavior can be removed with the corresponding removal methods.

public void RemoveStopPropagationEvent(string InputPlace, string HtmlEvent) public void RemoveStopPropagationEventListener(string InputPlace, string HtmlEventListener)

For example:

form.RemoveStopPropagationEvent("Button1", HtmlEvent.OnClick); form.RemoveStopPropagationEventListener("Button1", HtmlEventListener.Click);

4.8.6 Master Pages Event

The MasterPages methods provide a page-configuration mechanism in WebForms Core that can be used to implement a Master Pages style of page architecture.

Master Pages are normally assigned to the onload event of the body element. With this approach, a Layout is returned for every browser request and every route. The Layout contains the Master Pages event registration on the body element.

form.SetMasterPagesEvent("<body>", HtmlEvent.OnLoad);

After the body onload event occurs, WebFormsJS sends a GET request to the server through the Master Pages mechanism. Because the request generated by WebFormsJS contains the Post-Back header, the server can distinguish this request from the initial page request.

As a result, the server does not return the Layout again for this request. Instead, it returns the page associated with the requested route.

The general request flow can therefore be represented as:

1. The browser requests a route.
2. The server returns the Layout.
3. The Layout contains the Master Pages event on the body element.
4. The browser loads the Layout and the body onload event occurs.
5. WebFormsJS sends a GET request for the current route.
6. The request contains the Post-Back header.
7. The server recognizes the request as a WebForms Core post-back request.
8. The server returns the page content rather than returning the Layout again.

This approach separates the common page structure from the route-specific page content while retaining the HTML-based structure of WebForms Core.

4.8.7 SetMasterPagesEvent

The SetMasterPagesEvent method assigns the Master Pages behavior to an HTML event.

public void SetMasterPagesEvent(string InputPlace, string HtmlEvent, string OutputPlace = null)

The optional OutputPlace specifies where the page returned by the Master Pages request is placed.

form.SetMasterPagesEvent("<body>", HtmlEvent.OnLoad, "<main>");

In a typical Master Pages configuration, the event is assigned to the body onload event.

4.8.8 SetMasterPagesEventListener

The EventListener form is provided by SetMasterPagesEventListener.

public void SetMasterPagesEventListener(string InputPlace, string HtmlEventListener, string OutputPlace = null)

For example:

form.SetMasterPagesEventListener("<body>", HtmlEventListener.Load, "<main>");

The two methods provide the same Master Pages mechanism through the two event-definition forms used by WebForms Core.

Method	Event definition
SetMasterPagesEvent	HtmlEvent
SetMasterPagesEventListener	HtmlEventListener

4.8.9 Remove Master Pages Event

Master Pages event assignments can be removed with RemoveMasterPagesEvent and RemoveMasterPagesEventListener.

public void RemoveMasterPagesEvent(string InputPlace, string HtmlEvent) public void RemoveMasterPagesEventListener(string InputPlace, string HtmlEventListener)

For example:

form.RemoveMasterPagesEvent("<body>", HtmlEvent.OnLoad); form.RemoveMasterPagesEventListener("<body>", HtmlEventListener.Load);

4.8.10 Master Pages and Service Worker

The Master Pages configuration can be combined with a Service Worker to improve client-side efficiency. A Service Worker can cache the Layout on the client, allowing the common page structure to remain available locally while route-specific content is requested separately.

This approach can reduce repeated transfer of the same Layout and can improve the efficiency of applications that use a common page structure across many routes.

The Master Pages mechanism itself is responsible for the page-configuration flow. Service Worker caching is an additional capability that can be combined with it.

Note: The complete Master Pages architecture and its implementation patterns are documented separately in later sections.

4.8.11 Assign Confirm Event

The AssignConfirmEvent method attaches a confirmation dialog to an event that has already been assigned to an element.

Unlike the other Event and EventListener assignment methods, AssignConfirmEvent does not define a new event through an HtmlEventListener. It applies a confirmation requirement to an existing HTML event.

public void AssignConfirmEvent(string InputPlace, string HtmlEvent, string Text = "Are you sure you want to proceed?", string Type = "none", string Title = "Confirm", string OkText = "OK", string CancelText = "Cancel")

For example, an existing click event can be given a confirmation dialog:

form.SetGetEvent("DeleteButton", HtmlEvent.OnClick, "/delete"); form.AssignConfirmEvent("DeleteButton", HtmlEvent.OnClick);

When the user triggers the event, the confirmation is displayed first. The assigned event is executed only when the user confirms the operation.

The confirmation can be customized through the method parameters:

form.AssignConfirmEvent( "DeleteButton", HtmlEvent.OnClick, "Delete this item?", "warning", "Delete", "Delete", "Cancel");

Parameter	Description
InputPlace	The element containing the existing event.
HtmlEvent	The already assigned HTML event to which confirmation is applied.
Text	The confirmation message.
Type	The confirmation message type.
Title	The confirmation dialog title.
OkText	The confirmation button text.
CancelText	The cancellation button text.

Important: AssignConfirmEvent works with HtmlEvent and does not have an EventListener version. It assigns confirmation behavior to an event that is already assigned.

4.8.12 Removing Confirmation

An assigned confirmation can be removed with RemoveConfirmEvent.

public void RemoveConfirmEvent(string InputPlace, string HtmlEvent)

For example:

form.RemoveConfirmEvent("DeleteButton", HtmlEvent.OnClick);

Removing the confirmation does not represent removal of the underlying event itself. It removes the confirmation behavior associated with that event.

4.8.13 Event Control Methods

The following table summarizes the additional event-control methods provided in this section.

Method	Purpose
TriggerEvent	Programmatically triggers an event.
SetPreventDefaultEvent	Prevents the default action of an HTML event.
SetPreventDefaultEventListener	Prevents the default action through an EventListener.
RemovePreventDefaultEvent	Removes a prevent-default event assignment.
RemovePreventDefaultEventListener	Removes a prevent-default EventListener assignment.
SetStopPropagationEvent	Stops propagation of an HTML event.
SetStopPropagationEventListener	Stops event propagation through an EventListener.
RemoveStopPropagationEvent	Removes a stop-propagation event assignment.
RemoveStopPropagationEventListener	Removes a stop-propagation EventListener assignment.
SetMasterPagesEvent	Assigns the Master Pages mechanism to an HTML event.
SetMasterPagesEventListener	Assigns the Master Pages mechanism through an EventListener.
RemoveMasterPagesEvent	Removes a Master Pages event assignment.
RemoveMasterPagesEventListener	Removes a Master Pages EventListener assignment.
AssignConfirmEvent	Assigns confirmation behavior to an existing HTML event.
RemoveConfirmEvent	Removes confirmation behavior from an existing HTML event.

4.8.14 Summary

Other Events provide low-level and architectural event controls that complement the communication and execution mechanisms documented in the preceding sections.

TriggerEvent allows events to be triggered programmatically. Prevent-default and stop-propagation methods control browser event behavior. Master Pages events provide a page-configuration mechanism based on a Layout and route-specific page requests. Finally, AssignConfirmEvent adds confirmation behavior to an existing HTML event without creating a separate EventListener definition.