BoolToObjectConverter

Article
03/01/2023

The BoolToObjectConverter is a converter that allows users to convert a bool value binding to a specific object. By providing both a TrueObject and a FalseObject in the converter the appropriate object will be returned depending on the value of the binding.

The Convert method returns the TrueObject if the supplied value is true or the FalseObject otherwise.

The ConvertBack method returns true if the supplied value is equal to the TrueObject or false otherwise.

BaseConverter Properties

The following properties are implemented in the base class, public abstract class BaseConverter:

Property	Description
`DefaultConvertReturnValue`	Default value to return when `IValueConverter.Convert(object?, Type, object?, CultureInfo?)` throws an `Exception`. This value is used when CommunityToolkit.Maui.Options`.ShouldSuppressExceptionsInConverters` is set to `true`.
`DefaultConvertBackReturnValue`	Default value to return when `IValueConverter.ConvertBack(object?, Type, object?, CultureInfo?)` throws an `Exception`. This value is used when CommunityToolkit.Maui.Options`.ShouldSuppressExceptionsInConverters` is set to `true`.

ICommunityToolkitValueConverter Properties

The following properties are implemented in the public interface ICommunityToolkitValueConverter:

Property	Type	Description
`DefaultConvertReturnValue`	`object?`	Default value to return when `IValueConverter.Convert(object?, Type, object?, CultureInfo?)` throws an `Exception`. This value is used when CommunityToolkit.Maui.Options`.ShouldSuppressExceptionsInConverters` is set to `true`.
`DefaultConvertBackReturnValue`	`object?`	Default value to return when `IValueConverter.ConvertBack(object?, Type, object?, CultureInfo?)` throws an `Exception`. This value is used when CommunityToolkit.Maui.Options`.ShouldSuppressExceptionsInConverters` is set to `true`.

Syntax

The following examples will show how to use the BoolToObjectConverter to change the visibility of a Label control based on the specific value of a bound property MyValue.

XAML

Including the XAML namespace

In order to use the toolkit in XAML the following xmlns needs to be added into your page or view:

xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"

Therefore the following:

<ContentPage
    x:Class="CommunityToolkit.Maui.Sample.Pages.MyPage"
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml">

</ContentPage>

Would be modified to include the xmlns as follows:

<ContentPage
    x:Class="CommunityToolkit.Maui.Sample.Pages.MyPage"
    xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
    xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit">

</ContentPage>

Using the BoolToObjectConverter

The BoolToObjectConverter can be used as follows in XAML:

<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:toolkit="http://schemas.microsoft.com/dotnet/2022/maui/toolkit"
             x:Class="CommunityToolkit.Maui.Sample.Pages.Converters.BoolToObjectConverterPage">

    <ContentPage.Resources>
        <ResourceDictionary>
            <toolkit:BoolToObjectConverter x:Key="BoolToObjectConverter" TrueObject="42" FalseObject="0" />
        </ResourceDictionary>
    </ContentPage.Resources>

    <Label Text="The answer to the Ultimate Question of Life, the Universe and Everything."
           IsVisible="{Binding MyValue, Converter={StaticResource BoolToObjectConverter}}" />

</ContentPage>

C#

The BoolToObjectConverter can be used as follows in C#:

class BoolToObjectConverterPage : ContentPage
{
    public BoolToObjectConverterPage()
    {
        var label = new Label
        {
            Text = "The answer to the Ultimate Question of Life, the Universe and Everything."
        };

		label.SetBinding(
			Label.IsVisibleProperty,
			new Binding(
				nameof(ViewModels.MyValue),
				converter: new BoolToObjectConverter { TrueObject = 42, FalseObject = 0 }));

		Content = label;
    }
}

C# Markup

Our CommunityToolkit.Maui.Markup package provides a much more concise way to use this converter in C#.

using CommunityToolkit.Maui.Markup;

class BoolToObjectConverterPage : ContentPage
{
    public BoolToObjectConverterPage()
    {
        Content = new Label()
            .Text("The answer to the Ultimate Question of Life, the Universe and Everything.")
            .Bind(
                Label.IsVisibleProperty,
                static (ViewModel vm) => vm.MyValue,
                converter: new BoolToObjectConverter { TrueObject = 42, FalseObject = 0 });
    }
}

Examples

You can find an example of this converter in action in the .NET MAUI Community Toolkit Sample Application.

API

You can find the source code for BoolToObjectConverter over on the .NET MAUI Community Toolkit GitHub repository.