[Regression] RadioButton should support Null Value

[peruchali]

Description

Having a RadioButton with Value={x:Null} doesn't work anymore because of #31175 which doesn't allow null values for RadioButtons because coerceValue was added to set Value to the RadioButton itself.

I have a scenario where I add a "Don't know" option to my Radio Button list. This change breaks that and null is no longer accepted as RadioButton value.

This is a regression from MAUI 8

Steps to Reproduce

No response

Link to public reproduction project repository

No response

Version with bug

10.0.0-rc.2

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

.NET 8 (Please specify exact version)

Affected platforms

iOS, Android, Windows, macOS

Affected platform versions

No response

Did you find any workaround?

No workaround

Relevant log output

[peruchali]

@asi-evin FYI

[peruchali]

Workaround:

Use a converter:

/// <summary>
/// Helper converter that allows RadioButton's to have null values.
/// </summary>
internal sealed class RadioButtonNullValueConverter : IValueConverter
{
    /// <summary>
    /// A 'null' value.
    /// </summary>
    public static object Null { get; } = new();

    object? IValueConverter.Convert(object? value, Type targetType, object? parameter, CultureInfo culture) =>
        value is null ? Null : value;

    object? IValueConverter.ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture) =>
        value == Null ? null : value;
}

Then, you can use something like:

RadioButtonGroup.SelectedValue="{Binding MyNullableProperty, Mode=TwoWay, Converter={converters:RadioButtonNullValueConverter}}">

and in the null RadioButton:

<RadioButton
    Value="{Static converters:RadioButtonNullValueConverter.Null}"
    GroupName="...">

[asi-evin]

Yes, I was attempting to clear the radio buttons by setting the ViewModel value to NULL. I had a working solution, BUT one of the unit tests was failing (for the life of me I can't remember which one). So after some iterations, hair pulling, etc, I went with coercing the radio button value to SOMETHING as technically NULL is not on object, and it made sense to me that a radio button value SHOULD be an object.

Having said that, I see your situation as completely valid as well: I want to set NULL from the ViewModel and reflect that in the radio Buttons, you want to set NULL on the radion buttons and have that reflect in the ViewModel.

I can't make any promisses, but I can try and see if I can find an elegant solution to both our situations, or barring that, perhaps add a new property that will allow "NULL" as a value for select radio buttons? Spitting balling here... I could use a re-creation too, just so we're on the same page.

[kubaflo]

Hi! I’ve checked, and it looks like developers can assign a null value as a valid option for radio buttons in both native Swift and Kotlin implementations. So this seems to be a regression and should probably be fixed.

@asi-evin would you like to take this one, or should I help out with it? 🙂

Cheers!

[kubaflo]

@asi-evin I wonder if this would suffice? #32489

[asi-evin]

@asi-evin I wonder if this would suffice? #32489

I'd be ecstatic if that worked, but I beleive there's a Unit or UI test that is going to fail. We'll see...

Edit: and to answer previous question, yes I'll take the help. I might get a better chance to look at it later in the week.

[kubaflo]

@asi-evin alright! We need to summon the best /azp runner-man to verify tests @jfversluis then :)

[jfversluis]

🫡 reporting for duty