Introduction

ASP.NET AJAX’s ModalPopupExtender is a powerful tool for creating modal popups in web applications. However, one common challenge developers face is the need to execute specific JavaScript functions every time the modal is displayed. While the ModalPopupExtender provides the OnCancelScript and OnOkScript properties to handle events on cancellation and confirmation, it lacks an OnShowScript property, leading to some frustration.

In this blog post, we’ll explore how to work around this limitation and ensure that the desired JavaScript runs seamlessly when the modal is shown.

The Problem

You might need to execute a specific JavaScript function when your modal popup appears. A common scenario is when integrating features such as the TinyMCE editor in a textbox nestled within the modal. TinyMCE requires that the textbox be visible to initialize correctly, which means you need a way to trigger the initialization script at the right time.

The Solution

To execute JavaScript every time your modal is shown, you can utilize the shown event provided by the ModalPopupExtender. This approach allows for cleaner integration without relying on dummy controls or cumbersome workarounds.

Implementing the Solution

Here’s how you can set it up:

1. Add JavaScript to Your Page: You’ll need to attach your JavaScript functions to the shown event of the modal popup. This can typically be done in the pageLoad function.

2. Code Example: Below is an example code snippet demonstrating how to achieve this:

function pageLoad() {
    var popup = $find('ModalPopupClientID');
    popup.add_shown(SetFocus);
}

function SetFocus() {
    // Replace 'TriggerClientId' with the actual ID of your textbox
    $get('TriggerClientId').focus();
}

Breakdown of the Code

• pageLoad Function: This function runs when your page is loaded. It uses $find to get a reference to your ModalPopupExtender by its client ID (ModalPopupClientID is a placeholder and should be replaced with the actual ID).

• Adding the shown Event: The add_shown method is used to attach the SetFocus function to the shown event. This means that each time the modal is displayed, the SetFocus function will automatically run.

• SetFocus Function: In this function, we simply set the focus to the textbox that will be turned into a TinyMCE editor. Ensuring that it is visible will allow TinyMCE to initialize correctly without any issues.

Conclusion

By using the ModalPopupExtender’s shown event, you can smoothly integrate JavaScript executions necessary for your resource needs, like initializing TinyMCE editors. This approach not only simplifies your code but also ensures that your JavaScript functions are executed at the correct moment.

If you’re dealing with similar requirements in your ASP.NET applications, integrating JavaScript with modal popups has never been easier. Happy coding!