What is it?

In Mi-Form form, AfterOpen is an event that will be triggered when a form is opened. However, this is not true for mobile web forms on iOS and Android devices. .Net scripting is not executed in mobile web forms, instead you have explicitly invoke .Net scripting from client side. 

To be able to take advantage of .Net scripting, you can enable Run .NET AfterOpen event on sync feature for a template as picture below:

By doing this, all .Net scripting under AfterOpen event will be executed when the template is synced to client.

When can you use it?

1- You can setup initial form data, default values by querying back end database

2- You can create Grid data structure in .Net scripting