Developing page builder sections

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Sections are components which define the layout of widget zones within editable areas. You can define any number of different sections and allow content editors to choose them in the Pages application.

The system provides a built-in Default section containing a single widget zone. If you wish to use more advanced layouts in the page builder, you need to develop and register your own sections.

On this page

Developing sections

On a basic level, page builder sections are pieces of HTML output code containing widget zones. The main step in the development of a section is to create a partial view that defines the output.

Within the MVC architecture, the section partial view is served by a controller and a model is used to pass any required data. In many cases, sections can utilize a default controller and view model provided by the Xperience API. See the following scenarios for more information:

In both cases you can develop sections with properties, which allow content editors to adjust the section appearance or behavior directly in the administration interface. For sections with configurable properties, you need to create an additional model class that represents the section properties. For information about this more advanced scenario, see Defining section properties.

MVC Areas

Sections are designed to be used in the global scope and their code files must be placed in the application root of your MVC project (not in an MVC Area). Creating sections in MVC Areas may lead to unexpected behavior.

On a basic level, page builder sections are pieces of HTML output code containing widget zones. You can develop two types of sections:

In both cases you can develop sections with properties, which allow content editors to adjust the section appearance or behavior directly in the administration interface. For sections with configurable properties, you need to create an additional model class that represents the section properties. For information about this more advanced scenario, see Defining section properties.

Areas

Sections are designed to be used in the global scope and their code files must be placed in the application root of your Core project (not in an Area). Creating sections in Areas may lead to unexpected behavior.

Basic sections

Use the following process to develop a page builder section:

  1. Create a partial view with code that defines the required layout.
    • Use the WidgetZone extension method to identify locations where widgets can be placed. Every section must contain at least one widget zone – sections without widget zones are not supported.
    • We recommend storing section views in the ~/Views/Shared/Sections folder, and using a view name that matches the identifier assigned to the section upon its registration prefixed with the underscore (‘_’) character. Replace any period characters (‘.’) in the identifier with underscores (‘_’) in your view name.
    • Alternatively, you can use any required view location or name, and then specify it when registering the section.
    Example
    


 @using Kentico.PageBuilder.Web.Mvc
 @using Kentico.Web.Mvc

 <div>
     @Html.Kentico().WidgetZone()
 </div>

    Accessing the section’s page

    If you need to work with the data of the page containing the currently processed section, use the ComponentViewModel class as the view’s model and access its Page property. The property returns a TreeNode object representing the given page. If you need to load values from the fields of a specific page type, you can convert the TreeNode object to an instance of a specific page type wrapper class (the page containing the section must then be of the given page type).

  2. Register the section into the system. See Registering sections.

With this approach, the section’s view is automatically displayed using a default controller provided by the Xperience API. The values of any properties defined for the section can be passed to the view by using the default ComponentViewModel<TPropertyModel> class as the model.

  1. Create a partial view with code that defines the required layout.
    • Use the WidgetZoneAsync extension method (or the method’s <widget-zone /> Tag Helper alternative) to identify locations where widgets can be placed. Every section must contain at least one widget zone – sections without widget zones are not supported.
    • We recommend storing section views in the ~/Components/Sections/<SectionName> folder, and using a view name that matches the identifier assigned to the section upon its registration prefixed with the underscore (‘_’) character.
    • Alternatively, you can use any required view location or name, and then specify it when registering the section.
    Example
    


 @using Kentico.Web.Mvc
 @using Kentico.PageBuilder.Web.Mvc 

 <div>
     @await Html.Kentico().WidgetZoneAsync()
 </div>

    Accessing the section’s page

    If you need to work with the data of the page containing the currently processed section, use the ComponentViewModel class as the view’s model and access its Page property. The property returns a TreeNode object representing the given page. If you need to load values from the fields of a specific page type, you can convert the TreeNode object to an instance of a specific page type wrapper class (the page containing the section must then be of the given page type).

  2. Register the section into the system. See Registering sections.

With this approach, the section’s view is automatically displayed using logic provided by the Xperience API. The values of any properties defined for the section can be passed to the view by using the default ComponentViewModel<TPropertyModel> class as the model.

Example of section development

To see a scenario with full code samples which will guide you through the process of developing a simple section, visit Example - Developing a section with a configurable property.

Sections with a custom controller

When developing sections with advanced functionality, you may need to take full control over the section’s logic. You can do this by implementing the section’s controller and view model, in addition to the partial view. This allows you to run any custom code within the section’s controller, pass any type of required data to the view, or even switch between completely different views based on the current scenario.

The following steps describe the advanced development process for sections:

  1. Create a controller class for the section.
    • We recommend storing section controllers in the ~/Controllers/Sections folder.
  2. Make the controller inherit from the SectionController base class (available in the Kentico.PageBuilder.Web.Mvc namespace).
  3. Implement the default Index action in the controller, which is used to retrieve the section markup. The action must return the section’s HTML content, typically a partial view.
    • Do not disable POST requests for the Index action (e.g., by using the HttpGet attribute). POST requests to the Index action are used in the page builder feature.
    • Section controller actions used to retrieve the markup cannot be asynchronous (cannot use the asyncfunction declaration). Actions that render section markup are called as child actions when rendering the markup of an editable area, but MVC 5 does not support asynchronous child controller actions.
    


 public class DefaultSectionController : SectionController
 {
     // GET action used to retrieve the section markup
     public ActionResult Index()
     {
         return PartialView("Sections/_DefaultSection");
     }
 }
  4. Create any required view model classes used to pass data from the section controller to the partial view.
    • We recommend storing section models in the ~/Models/Sections/<section name> folder.
  5. Prepare a partial view that defines the output of the section.
    • Use the WidgetZone extension method to identify locations where widgets can be placed. Every section must contain at least one widget zone – sections without widget zones are not supported.
    • We recommend storing section views in the ~/Views/Shared/Sections folder.
  6. Register the section into the system. See Registering sections.

With this advanced development approach, you have full responsibility and control over the section’s controller, view model, and partial view.

Accessing the data of the current page

If you need to access fields of the page containing the currently processed section, obtain an instance of the IPageDataContextRetriever service (we recommend using dependency injection) and call its Retrieve<TPageType> method. Specify either a TreeNode object or a page type wrapper class as the generic parameter. The method returns an IPageDataContext<TPageType> object with the following properties:




// Contains an instance of the IPageDataContextRetriever service (e.g., obtained via dependency injection)
private readonly IPageDataContextRetriever pageDataContext;

// Gets the page of the Article page type where the currently processed section is placed
var article = pageDataContext.Retrieve<Article>().Page;

Accessing the data of the current page in POST actions

Fields of the page the section is rendered on are by default not accessible in controller actions that handle POST requests. Such requests do not contain sufficient information to identify the page from which they originate. 

To access page data in POST actions, you need to include information about the current page into the data submitted by the corresponding form in the section’s output – call the Html.Kentico().PageData extension method within the given form tag in your section view.

Example



using System.Web.Mvc.Ajax
using Kentico.Web.Mvc
using Kentico.PageBuilder.Web.Mvc

...

@using (Ajax.BeginForm("PostAction", "CustomSection", null, new AjaxOptions
{
    HttpMethod = "POST",
    UpdateTargetId = "sectionForm"
}, new { id = "sectionForm" }))
{
    @Html.Kentico().AntiForgeryToken()
    @Html.Kentico().PageData()
    ...
    <input type="submit" value="Submit" />
}

The method renders a hidden form field that persists information about the current page. The page data can be retrieved via IPageDataContextRetriever.Retrieve<TPageType> in the corresponding POST action.

Sections based on a view component

The basic implementation of a section consists of only a partial view (and possibly a properties class). You may need additional logic, for example if you need to:

  • react to the configuration of the section’s properties
  • perform interactions based on the page where the section is rendered
  • execute general business logic not suitable for views (e.g., database operations)

For this purpose, you can develop sections based on ASP.NET Core view components. Such sections consist of a view component class and the corresponding partial view it renders.

Implementing a section based on a view component follows this general process:

  1. Create a view component class for the section.

    • We recommend storing section view components in the ~/Components/Sections/<SectionName> folder together with other files required by the section.

  2. Implement the component’s Invoke or InvokeAsync method (the synchronous and asynchronous approaches are both supported, this choice depends solely on your requirements).

    • The system invokes the view component when the section is inserted via the page builder. During the invocation, the system passes the section’s properties (the ComponentViewModel class) into the component’s Invoke method. For this reason, the method’s signature needs to declare the ComponentViewModel parameter. For sections with custom properties, you need to specify the properties class as the generic parameter.

      


  // The signature of a view component's InvokeAsync method for sections without custom properties
  public async Task<IViewComponentResult> InvokeAsync(ComponentViewModel sectionProperties)

  // The signature of a view component's InvokeAsync method for sections with custom properties
  public async Task<IViewComponentResult> InvokeAsync(ComponentViewModel<TSectionPropertiesClass> sectionProperties)

  3. To the return statement of the component’s Invoke method, add the full relative path to the component’s partial view. For example:

    


 return View("~/Components/Sections/MySection/_MySection.cshtml", model);

  4. Create any required view model classes used to pass data from the section view component to the partial view.

    • We recommend storing section models in the ~/Components/Sections/<SectionName> folder together with other files required by the section.

  5. Prepare a partial view that defines the layout of the section.

    • Use the WidgetZoneAsync extension method (or the method’s <widget-zone /> Tag Helper alternative ) to mark locations within the layout where widgets can be placed. Every section must contain at least one widget zone – sections without widget zones are not supported.
    • We recommend storing section views in the ~/Components/Sections/<SectionName> folder together with other files required by the section.

  6. Register the section into the system. See Registering sections.

When the section is inserted using the page builder, the system invokes the corresponding view component and renders its partial view. Using this approach, you can decouple business and view-layer code, maintaining separation of concerns.

Accessing the data of the current page

If you need to access fields of the page where the section is currently rendered, use the Page property of the ComponentViewModel class (from the component’s Invoke method).




// Retrieves the name of the page on which the section is currently rendered
string name = sectionProperties.Page.DocumentName;

Handling POST actions

If your section needs to communicate with the server using POST actions, create a custom controller class containing the required action methods and logic. We recommend storing the class in the ~/Components/Sections/<SectionName> folder together with other files required by the section.

Fields of the page the section is rendered on are by default not accessible in controller actions that handle POST requests. Such requests do not contain sufficient information to identify the page from which they originate. To access page data in POST actions, you need to include information about the current page into the data submitted by the corresponding form in the section’s output – call the Html.Kentico().PageData extension method (or the method’s Tag Helper alternative) within the given form tag in your section view.




@using Kentico.Web.Mvc
@using Kentico.PageBuilder.Web.Mvc

<form asp-controller="SectionPostActionsController" asp-action="HandlePost" id="form">

    ...

    @Html.Kentico().PageData()

    <input type="submit" value="Submit" />
</form>

The method renders a hidden form field that persists information about the current page. The page data can be retrieved via the IPageDataContextRetriever service in the corresponding controller action. 

Obtain an instance of the IPageDataContextRetriever service (we recommend using dependency injection) and call its Retrieve<TPageType> method. Specify either a TreeNode object or a page type wrapper class as the generic type parameter. The method returns an IPageDataContext<TPageType> object that contains the current page object in its Page property. You can also access the metadata and evaluate the permissions and authentication requirements of the page via the object’s Metadata and Security properties.




// Contains an instance of the IPageDataContextRetriever service (e.g., obtained via dependency injection)
private readonly IPageDataContextRetriever pageDataContext;

// Gets the page of the Article page type where the currently processed section is placed
var article = pageDataContext.Retrieve<Article>().Page;

Registering sections

For sections to become available in the page builder, they need to be registered into the system. Register sections using the RegisterSection assembly attribute (available in the Kentico.PageBuilder.Web.Mvc namespace).

To register basic sections (without a custom controller class), we recommend adding the assembly attributes to a dedicated code file. For example, you can create a file named PageBuilderComponentRegister.cs in your project’s ~/App_Start folder and use it to register your page builder components. For basic sections, specify the following attribute parameters:

  • Identifier – the unique identifier of the section. We recommend using a unique prefix in your section identifiers to prevent conflicts when deploying sections to other projects, for example matching your company’s name.

  • Name – the name used to identify the section when displayed in the administration interface.

  • PropertiesType – only required for sections with properties. Specifies the System.Type of the section’s property model class.

  • (Optional) CustomViewName – specifies the name and location of the view that defines the section’s output. If not set, the system searches for a corresponding _<Identifier>.cshtml view in the ~/Views/Shared/Sections folder (any period characters ‘.’ in the identifier are replaced by underscores ‘_’).

    Basic section registration example
    


  [assembly: RegisterSection("CompanyName.DefaultSection", "Default section", typeof(CustomSectionProperties), "Sections/_DefaultSection")]

For sections with a custom controller, you can add the assembly attribute directly into the controller code file (above the controller class). In this case, specify the following attribute parameters:

  • Identifier – the unique identifier of the section. We recommend using a unique prefix in your section identifiers to prevent conflicts when deploying sections to other projects, for example matching your company’s name.

  • ControllerType – the System.Type of the section’s controller class.

  • Name – the name used to identify the section when displayed in the administration interface.

    Controller section registration example
    


  [assembly: RegisterSection("CompanyName.DefaultSection", typeof(DefaultSectionController), "Default section")]

When registering any type of section, you can also set the following optional attribute properties:

  • Description – the description of the section displayed as a tooltip.
  • IconClass – the font icon class displayed when viewing the sections in the section list.



[assembly: RegisterSection("CompanyName.DefaultSection", typeof(DefaultSectionController), "Default section", Description = "A default section with one widget zone.", IconClass="icon-box")]

To register basic sections (without a view component class), we recommend adding the assembly attributes to a dedicated code file. For example, you can create a file named ComponentRegister.cs in your project’s ~/Components folder and use it to register your page builder components. For basic sections, specify the following attribute parameters:

  • Identifier – the unique identifier of the section. We recommend using a unique prefix in your section identifiers to prevent conflicts when deploying sections to other projects, for example matching your company’s name.

  • Name – the name used to identify the section when displayed in the administration interface.

  • PropertiesType – only required for sections with properties. Specifies the System.Type of the section’s property model class.

  • CustomViewName – specifies the name and location of the view that defines the section’s output. If not set, the system searches for a corresponding  _<Identifier>.cshtml  view in the ~/Views/Shared/Sections folder (any period characters ‘.’ in the identifier are replaced by underscores ‘_’).

    Basic section registration example
    


  [assembly: RegisterSection("CompanyName.DefaultSection", "Default section", typeof(CustomSectionProperties), "~/Components/Sections/_MySection.cshtml")]

For sections based on a view component, you can add the assembly attribute directly into the view component code file. In this case, specify the following attribute parameters:

  • Identifier – the unique identifier of the section. We recommend using a unique prefix in your section identifiers to prevent conflicts when deploying sections to other projects, for example matching your company’s name.

  • ViewComponentType – the System.Type of the section’s view component class.

  • Name – the name used to identify the section when displayed in the administration interface.

  • PropertiesType – only required for sections with properties. Specifies the System.Type of the section’s property model class.

    View component section registration example
    


  [assembly: RegisterSection("CompanyName.DefaultSection", typeof(DefaultSectionViewComponent), "Default section", typeof(CustomSectionProperties))]

When registering any type of section, you can also set the following optional attribute properties:

  • Description – the description of the section displayed as a tooltip.
  • IconClass – the font icon class displayed when viewing the sections in the section list.



[assembly: RegisterSection("CompanyName.DefaultSection", typeof(DefaultSectionViewComponent), "Default section", Description = "A default section with one widget zone.", IconClass="icon-box")]

Localizing section metadata

To allow content editors to experience the page builder in their preferred UI culture, you can localize the Name and Description values of sections.

Assigning a default section

Editable areas in the page builder have a default section, which is automatically added when the area is empty. This includes new areas where content editors have not yet placed any other section, and scenarios where an editor removes the last section from an area.

By default, the system’s built-in Default section is used for this purpose. For most websites, we recommend replacing the default section with your own to ensure that the page builder output code exactly matches the requirements of your website’s styling and design.

To specify a global default section, extend the code that registers the page builder feature in your live site project:

  1. Create a PageBuilderOptions object and set its DefaultSectionIdentifier property to the identifier of the appropriate section.

  2. To disable the system’s built-in Default section, also set the RegisterDefaultSection property to false.

    Warning: If your site already has existing pages that use the page builder, replace all occurrences of the Default section in page content before you disable it. Otherwise an error will occur on the given pages.

  3. Pass the PageBuilderOptions object as the parameter of the UsePageBuilder method.

    


 var options = new PageBuilderOptions()
 {
     // Specifies a default section for the page builder feature
     DefaultSectionIdentifier = "CompanyName.DefaultSection",
     // Disables the system's built-in 'Default' section
     RegisterDefaultSection = false
 };

 // Enables the page builder feature
 builder.UsePageBuilder(options);

  1. Create a PageBuilderOptions object and set its DefaultSectionIdentifier property to the identifier of the appropriate section.

  2. To disable the system’s built-in Default section, also set the RegisterDefaultSection property to false.

    Warning: If your site already has existing pages that use the page builder, replace all occurrences of the Default section in page content before you disable it. Otherwise, accessing the pages will result in an error.

  3. Pass the PageBuilderOptions object as the parameter of the UsePageBuilder method.

    


         public void PageBuilderAssignDefaultSection(IServiceCollection services)
         {
             PageBuilderOptions options = new PageBuilderOptions()
             {
                 DefaultSectionIdentifier = "CompanyName.DefaultSection",
                 // Disables the system's built-in 'Default' section
                 RegisterDefaultSection = false
             };

             services.AddKentico(features =>
                 features.UsePageBuilder(options));
         }

Empty editable areas now use the new default section. The change does NOT modify the sections within existing page builder content.

You can also override the global default section for individual editable areas:

  1. Prepare an EditableAreaOptions object.
  2. Set the object’s DefaultSectionIdentifier property to match the identifier of the section which you want to use as default.
  3. Assign the object as a parameter of EditableArea methods in your views.



<div>
    @{
        var optionsDefaultSection = new EditableAreaOptions
        {
            DefaultSectionIdentifier = "LearningKit.Sections.Col5050"
        };
    }
    @Html.Kentico().EditableArea("areaWithSection", optionsDefaultSection)
</div>
  1. Prepare an EditableAreaOptions object.
  2. Set the object’s DefaultSectionIdentifier property to match the identifier of the section which you want to use as default.
  3. Assign the object as a parameter of EditableAreaAsync extension methods (or the Tag Helper alternative) in your views.



<div>
    @{
        var optionsDefaultSection = new EditableAreaOptions
        {
            DefaultSectionIdentifier = "LearningKit.Sections.Col5050"
        };
    }
    @await Html.Kentico().EditableAreaAsync("areaWithSection", optionsDefaultSection)
</div>

Limiting widgets allowed in zones

You can define widget restrictions for individual zones defined within sections. To limit which widgets can be added to a specific zone:

  1. Edit the partial view of the section where the widget zone is defined.
  2. Create a list of strings containing the identifiers of widgets you want to allow in the zone. See Developing widgets to learn more about widget identifiers. For identifiers of the default system widgets, check the system widget reference.
  3. Assign the list of identifiers to the allowedWidgets named parameter of the widget zone extension method.

The allowed widgets parameter works as a whitelist – you list widgets that you want to allow in the zone, and all others are automatically excluded. When the allowed widgets parameter is not specified, all registered widgets can be added to the zone.

The widget limiting feature is intended as a way to set guidelines for content editors, not as a security measure. When you limit a zone, existing instances of widgets placed in the zone are not validated or removed.

Editable area restrictions

Widget zone restrictions are combined with any widget restrictions set for the Page Builder editable area containing the section. Both sets of restrictions apply to create the final list of allowed widgets for the zone.

Example - Limiting widgets in a zone



<div>
    @{
        var widgetsWhitelist = new[] { Kentico.Content.Web.Mvc.SystemComponentIdentifiers.FORM_WIDGET_IDENTIFIER,
                                       "LearningKit.Widgets.NumberWidget",
                                       "LearningKit.Widgets.SomeOtherWidget" };
    }
    @Html.Kentico().WidgetZone(allowedWidgets: widgetsWhitelist)
</div>
Example - Limiting widgets in a zone



<div>
    @{
        var widgetsWhitelist = new[] { Kentico.Content.Web.Mvc.SystemComponentIdentifiers.FORM_WIDGET_IDENTIFIER,
                                       "LearningKit.Widgets.NumberWidget",
                                       "LearningKit.Widgets.SomeOtherWidget" };
    }
    @await Html.Kentico().WidgetZoneAsync(allowedWidgets: widgetsWhitelist)
</div>

Ensuring correct transfer of widgets between section types

When a user changes the section type in the Page Builder interface, widgets are moved to the new section’s widget zones automatically based on the order in which the zones are specified in the section code. This may require additional work from content editors to get the desired page layout.

To ensure that widgets are moved to correct zones when the section type is changed:

  1. Add an identifier to each zone, which creates so-called named widget zones.
  2. Use the same identifier for corresponding zones within all of your widget sections.

When a section type is changed, the system moves widgets to matching named zones.

Transfer of widgets between section types

Example - Named widget zone



<div>
    @Html.Kentico().WidgetZone("main")
</div>
Example - Named widget zone



<div>
    @await Html.Kentico().WidgetZoneAsync("main")
</div>

Storing files for use in the page builder

You may wish to develop sections that use or display various files. You can store such files in the system either as page attachments or using media libraries. These two approaches vary in different ways:

  • Page attachment files are associated only with a specific page. You should store media files as page attachments only if the files are considered to be a content of a particular page (e.g. a language specific variant of an image).
  • Media library files are available for all pages of a particular site. You should store files using media libraries when the file content is reusable or the files are more relevant to the general visual design of the page than to its content (e.g. a background image used on all pages with a similar layout).

This is important to remember especially when creating custom page templates from existing pages. New pages created using templates do not display any page attachments, because the attachments stay as content bound to the original pages. On the other hand, pages based on templates display media library files automatically.

Adding scripts and styles for sections

To add JavaScript and CSS styles required by your page builder sections, place script and stylesheet files into sub-folders under the ~/Content/Sections directory of your MVC project (you may need to create the Sections directory). Use sub-folders that match the identifiers of individual sections, or a Shared sub-folder for assets used by multiple sections.

The system automatically creates bundles containing all .js and .css files located under ~/Content/Sections. The bundles are then linked on all pages with page builder editable areas.

The same bundles also contain script and stylesheet files added for widgets in the ~/Content/Widgets directory and inline property editors in the ~/Content/InlineEditors directory (inline editor scripts and styles are only included in the administration bundles, which are linked when pages are displayed in Edit mode within the Pages application).

CSS notes- Only use the ~/Content/Sections directory to add basic styles that are required for the section to render correctly. Any site-specific styles that finalize the live site design of the section should be handled separately within the given site’s main stylesheet. - To avoid potential conflicts between styles from other third-party components, we recommend adding a unique prefix to your CSS classes and identifiers (for example #CompanyName-mid-column), or employ similar measures to ensure their uniqueness. - Do not make any assumptions about the relative order of the source CSS in the resulting bundles – individual stylesheet files contained in the bundle may or may not precede each other.

To add JavaScript and CSS styles required by your sections, we recommend placing script and stylesheet files into sub-folders under:

  • ~/wwwroot/PageBuilder/Public/Sections/<SectionName> – scripts and styles intended for the live site.
  • ~/wwwroot/PageBuilder/Admin/Sections/<SectionName> – scripts and styles intended for the administration interface (when working with the section in the page builder editing interface).

You can use sub-folders that match the identifiers of individual sections, or a Shared sub-folder for assets used by multiple sections. Note that this recommendation only applies when using the default configuration of the bundling support provided by Xperience and may be different for your project. See  Bundling static assets of builder components.

CSS notes- Only use the specified directories to add basic styles that are required for the section to render correctly. Any site-specific styles that finalize the live site design of the section should be handled separately within the given site’s main stylesheet. - To avoid potential conflicts between styles from other third-party components, we recommend adding a unique prefix to your CSS classes and identifiers (for example #CompanyName-mid-column), or employ similar measures to ensure their uniqueness.

Initializing section scripts

If you need to initialize scripts (for example call a function on page load or register an event listener), you can add script tags directly into the view code of your page builder sections. However, you need to keep the following in mind:

  • Do not rely on the order of execution of multiple script tags within one section. The order of their execution may be different in the page builder interface than on the live site.

  • If you declare variables within section script tags, the variables are defined in the global namespace. To prevent conflicts on pages containing multiple instances of the same section, wrap the scripts into a self-executing anonymous function.

  • If you use assets stored in the ~/Content/Sections folder within the section views, the related bundles are added at the end of the HTML document’s body tag. Such assets are not available in the section code during the page load process. A solution is to run the initialization script during the DOMContentLoaded event. However, sections in the page builder interface may be added dynamically after the page is loaded. In this case, the DOMContentLoaded event has already occurred and will not fire again. For example, the following script demonstrates how to reliably call a custom function on page load:

    


  @using Kentico.PageBuilder.Web.Mvc
  @using Kentico.Web.Mvc

  <div>
      @Html.Kentico().WidgetZone()
  </div>
  <script type="text/javascript">
  (function () {
      if (document.readyState === "loading") {
          // Calls the function during the 'DOMContentLoaded' event, after the HTML document has been completely loaded
          document.addEventListener("DOMContentLoaded", function () {
              customFunction();
          });
      } else {
          // Calls the function directly in cases where the section is rendered dynamically after 'DOMContentLoaded'
          customFunction();
      }
  })();
  </script>

Apart from initialization code, avoid linking or executing scripts directly within section views. This could lead to duplicated scripts on pages that contain multiple instances of the same section.