Power Tools Custom Code - MAUI

ASP.NET Zero Power Tools generates code that can be fully regenerated whenever you change an entity. The Custom Code feature lets you add your own code to the generated pages and classes so that your additions survive regeneration.

This page covers how Custom Code works in the MAUI Blazor Hybrid mobile app. The MAUI app ships alongside every UI framework, so this page applies whether your web project is Angular, ASP.NET Core MVC, or React.

Enabling Custom Code

MAUI Custom Code has two layers, each with its own requirements:

Requirements

Region slots are available on any project that supports MAUI code generation (v13.3+). Turn on the Mobile switch and the generated .razor pages will include az:begin / az:end markers.

Partial class files require all three conditions:

1. The Mobile switch is on.
2. The Generate Overridable Entity switch is on.
3. The project version is v15.5 or later.

On a v13.3–v15.4 project the Mobile switch still produces pages with region slots, but the .custom.cs companion files are not generated.

Generate Overridable Entity alone (without Mobile) customizes the server side and the web client but leaves the MAUI app untouched.

Detail page. ViewProduct.custom.cs is generated only when the entity's MAUI view page is enabled — the Create View option that appears under Mobile in the Visual Studio extension.

How It Works

MAUI uses a third approach, different from Angular's base/subclass split and React's hook files:

Because your code is a partial of the same class rather than a subclass, there is no separate type to register and no route to update - the component is still ProductIndex. The generated .razor.cs beside it keeps being rewritten on every run, so new entity properties keep flowing in.

Partial Class Files

For a Product entity with namespace Inventory, Power Tools generates these files under <YourProject>.Maui\Pages\Inventory\:

Each .custom.cs file starts out as an empty partial:

namespace MyCompany.MyProject.Maui.Pages.Inventory;

public partial class ProductIndex
{
}

Add fields, methods, or lifecycle overrides (such as OnInitializedAsync from Blazor's ComponentBase) here. Because it is the same class, you can reach any protected member the generated .razor.cs declares without any extra plumbing.

Example - Running Custom Logic After the Page Loads

namespace MyCompany.MyProject.Maui.Pages.Inventory;

public partial class ProductIndex
{
    private int _lowStockCount;

    protected override async Task OnInitializedAsync()
    {
        await base.OnInitializedAsync();
        _lowStockCount = await CountLowStockAsync();
    }

    private Task<int> CountLowStockAsync()
    {
        // your logic here
        return Task.FromResult(0);
    }
}

Razor - Preserved Region Slots

MAUI .razor pages contain named az:begin / az:end markers. You can place custom markup between these markers and it will be preserved on regeneration. The rest of the page is fully regenerated.

Slot Reference

Example - Adding a Custom List Field

<!-- az:begin(list-fields) -->
<div class="row">
    <div class="text-muted col-6">Margin</div>
    <div class="fw-semibold col-6">
        @(model.Product.Margin?.ToString("P0") ?? "-")
    </div>
</div>
<!-- az:end(list-fields) -->

Example - Adding a Custom Form Field

<!-- az:begin(form-fields) -->
<div class="d-flex flex-column mb-4">
    <label class="form-label fw-semibold">@L("InternalNotes")</label>
    <InputTextArea @bind-Value="CreateOrEditProductModel.InternalNotes" class="form-control form-control-solid" rows="3" />
</div>
<!-- az:end(form-fields) -->

After regeneration, your markup stays in place while the rest of the page is updated with any new entity properties.

Preserved Region Rules

The az:begin / az:end markers follow these rules:

Server Side

The MAUI app consumes the same application services as the web client, so the server-side extension files are the ones described on the Angular, MVC, and React pages. They are generated once for the entity regardless of which clients you target.

Safety Features

Power Tools includes safety mechanisms to prevent code loss:

• Abort on malformed markers: If region markers are broken (unclosed, nested, duplicated, mismatched), the entire file is left untouched. No partial merge ever occurs.
• Orphan rescue: If a region name existed in the old file but not in the newly generated output (for example, if a template update removes a slot), the content is saved to a sidecar file (<filename>.orphaned.txt) and a warning is shown. Content is never silently dropped.
• Ownership guard: Toggling the Generate Overridable Entity switch on an entity that already has generated .custom.cs files is handled in both directions:
  • Turning it off points a fully generated template back at the file that holds your code. Power Tools detects your code and refuses to overwrite it.
  • Turning it on makes a path that used to be fully generated developer-owned. The file already sitting there is old generated code, so Power Tools deletes it and lets the template write the new split - saving a copy as <filename>.bak beside it first. If you had hand-edited that file, your changes are in the .bak, not in the regenerated one.

Next

How to Create & Edit Power Tools Templates