[LumeoForm] Source Generator

Hand-writing a Blazor form for every POCO — picking the right input per property, wiring @bind-Value, repeating <FormField Label="…" Required> — is pure boilerplate. The [LumeoForm] Roslyn source generator does it for you at compile time.

Annotate any class with [LumeoForm] and make it partial. The generator emits a static RenderForm(model, onValidSubmit) method that returns a ready-to-use RenderFragment.

1. Annotate a POCO

using System.ComponentModel.DataAnnotations;
using Lumeo;

[LumeoForm(Title = "Contact us", SubmitLabel = "Send message")]
public partial class ContactFormModel
{
    [Required, StringLength(80, MinimumLength = 2)]
    [Display(Name = "Full name", Description = "As it should appear on the invoice.")]
    public string Name { get; set; } = "";

    [Required, DataType(DataType.EmailAddress)]
    public string Email { get; set; } = "";

    [DataType(DataType.Password), StringLength(64, MinimumLength = 8)]
    public string Password { get; set; } = "";

    [Range(1, 120)]
    public int Age { get; set; } = 25;

    public bool Subscribe { get; set; }
    public ContactPreference Preference { get; set; }
}

public enum ContactPreference { Email, Phone, SmsMessage }

2. Render it

Use the generated RenderForm method as a RenderFragment — either assign it to a field and invoke it as @_formFragment or render it directly.

@page "/contact"
@using MyApp.Models

<h1>Contact</h1>

@ContactFormModel.RenderForm(_model, EventCallback.Factory.Create<ContactFormModel>(this, HandleSubmit))

@code {
    private readonly ContactFormModel _model = new();

    private Task HandleSubmit(ContactFormModel m)
    {
        // _model is validated — persist it.
        return Task.CompletedTask;
    }
}

3. Live demo

The form below was generated from ContactFormModel at build time — no hand-written Razor.

Supported property types

Property type	Generated component	Notes
`string`	`<Input />`	Also honours `[DataType(DataType.EmailAddress)]` → `type="email"`.
`string` + `[DataType(Password)]`	`<PasswordInput />`	Masked entry, strength meter.
`int`, `long`, `double`, `decimal`, …	`<NumberInput />`	Coerces to/from `double?` internally.
`bool`	`<Checkbox />`	Bound via `Checked` / `CheckedChanged`.
`DateTime`, `DateTimeOffset`	`<DatePicker />`	Uses the picker's `DateTimeValue` binding.
`DateOnly`	`<DatePicker />`	Default `DateOnly?` binding.
`enum`	`<Select />` + one `<SelectItem />` per member	Labels PascalCase-split to "Sms Message".

Validation attributes

The generator wires the built-in DataAnnotationsFormValidator into every generated form, so any standard System.ComponentModel.DataAnnotations attribute runs at submit time without extra code:

[Required] — also marks the field visually via FormField.Required.
[StringLength(max, MinimumLength = n)]
[Range(min, max)]
[DataType(DataType.EmailAddress)] / [DataType(DataType.Password)] — influences input choice.
[Display(Name = "…", Description = "…")] — Name → field label, Description → help text.

Attribute options

Property	Type	Default	Description
`Title`	`string?`	`null`	Optional heading rendered above the form.
`IncludeSubmitButton`	`bool`	`true`	Whether to append a submit button at the end.
`SubmitLabel`	`string`	`"Submit"`	Label on the generated submit button.

Known limitations

Target classes must be marked partial.
Only public read/write properties with a public setter are rendered.
Collections, nested records, and custom value types are skipped — use a hand-written form for those.
Flag enums render as a single Select; use a hand-written ToggleGroup if you need multi-select.
Horizontal layout, field ordering, and custom input components require a manual form (the generator emits a vertical stack).