# RadioGroup

> One choice of a few, all in view — a radio per option under a caption. The same shape as Dropdown: value is a two-way Binding<T>, options default to the enum's members worded by their labels, and a template says what one option reads. Reach for it when there are two to six options and the person should see them before choosing.

<!-- id: ui-radio-group · area: ui · stability: stable · html: https://osysharp.com/reference/ui/radio-group/ -->

## Summary        {#summary}

A dropdown hides its options until it is opened; a radio group shows them. That is the right trade when there are
only a few, when they explain each other, and when the person is filling in something they may never have seen
before — a form anyone may have to use. `RadioGroup` binds a value exactly as `Dropdown` does.

```osy title="a question with its answers in view" test app=ui-radio-group
enum Venue { [Label("A café")] Cafe, [Label("A gallery")] Gallery, [Label("Somewhere else")] Other }

[Route("/listing")] [Render(CSR)] [AllowAnonymous]
component ListingPage() {
  Venue kind = Venue.Cafe;
  render {
    Stack(gap: 4, p: 6) {
      RadioGroup("What kind of venue is it?", value: kind, hint: "Choose the one most visitors would say.");
      Text("You chose: " + kind.Label);
    }
  }
}
```

## Signature      {#signature}

```osy syntax
RadioGroup<T>(string label, Binding<T> value, T[] options = T.Members, string hint = "", bool disabled = false)
  { option => <what one option reads> }   // optional; defaults to its Label
```

## Description    {#description}

### Radio or dropdown?   {#choose}

Two to six options a person should compare: `RadioGroup`. Many options, or options the person already knows (a
country, a currency): `Dropdown`. Yes or no: `Checkbox` or `Switch`.

### Over rows rather than an enum?   {#rows}

Pass `options:` and a template, as with `Dropdown`: `RadioGroup("Ship with", value: order.Carrier, options: carriers)
{ c => Text(c.Name); }`.

### How do I drive it in a test?   {#test}

Press an option by its words — `Ui.Click("A gallery")` — and read it back with `Assert.Checked("A gallery")`.

## See also       {#see-also}

- [control — foreign UI controls (charts, grids, maps)](https://osysharp.com/reference/ui/controls/) — `Dropdown`, `Checkbox`, `Switch` and the rest of the kit's value controls
- [Validation](https://osysharp.com/reference/ui/validation/) — saying what is wrong with an answer