VariableMultiValueConverter

The VariableMultiValueConverter is a converter that allows users to convert bool values via a MultiBinding to a single bool. It does this by enabling them to specify whether All, Any, None or a specific number of values are true as specified in ConditionType.

The Convert method returns the supplied values converted to an overall bool result based on the ConditionType defined.

The ConvertBack method will only return a result if the ConditionType is set to MultiBindingCondition.All.

BaseConverter Properties

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

ICommunityToolkitValueConverter Properties

The following properties are implemented in the public interface ICommunityToolkitValueConverter:

Syntax

The following examples show how to make a Label invisible based when at least 2 of the values in a MultiBinding evaluate to true.

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 VariableMultiValueConverter

The VariableMultiValueConverter 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.VariableMultiValueConverterPage">

    <ContentPage.Resources>
        <ResourceDictionary>
            <toolkit:VariableMultiValueConverter 
                x:Key="VariableMultiValueConverter"
                ConditionType="LessThan"
                Count="2" />
        </ResourceDictionary>
    </ContentPage.Resources>

    <Label Text="At least 2 toppings must be selected.">
        <Label.IsVisible>
            <MultiBinding Converter="{StaticResource VariableMultiValueConverter}">
                <Binding Path="IsCheeseSelected" />
                <Binding Path="IsHamSelected" />
                <Binding Path="IsPineappleSelected" />
            </MultiBinding>
        </Label.IsVisible>
    </Label>

</ContentPage>

C#

The VariableMultiValueConverter can be used as follows in C#:

class VariableMultiValueConverterPage : ContentPage
{
    public VariableMultiValueConverterPage()
    {
        var label = new Label
        {
            Text = "At least 2 toppings must be selected."
        };

        label.SetBinding(
            Label.IsVisibleProperty,
            new MultiBinding
            {
                Converter = new VariableMultiValueConverter
                {
                    ConditionType = MultiBindingCondition.LessThan,
                    Count = 2
                },
                Bindings = new List<BindingBase>
                {
                    new Binding(static (ViewModel vm) => vm.IsCheeseSelected),
                    new Binding(static (ViewModel vm) => vmIsHamSelected),
                    new Binding(static (ViewModel vm) => vmIsPineappleSelected)
                }
            });

        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 VariableMultiValueConverterPage : ContentPage
{
    public VariableMultiValueConverterPage()
    {
        Content = new Label()
            .Text("At least 2 toppings must be selected.")
            .Bind(
                Label.IsVisibleProperty,
                new List<BindingBase>
                {
                    new Binding(static (ViewModel vm) => vm.IsCheeseSelected),
                    new Binding(static (ViewModel vm) => vm.IsHamSelected),
                    new Binding(static (ViewModel vm) => vm.IsPineappleSelected)
                },
                converter: new VariableMultiValueConverter
                {
                    ConditionType = MultiBindingCondition.LessThan,
                    Count = 2
                });
    }
}

Properties

MultiBindingCondition

The MultiBindingCondition enumeration defines the following members:

• None - None of the values should be true.
• All - All of the values should be true.
• Any - Any of the values should be true.
• Exact - The exact number as configured in the Count property should be true.
• GreaterThan - Greater that the number as configured in the Count property should be true.
• LessThan - Less than the number as configured in the Count property should be true.

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 VariableMultiValueConverter over on the .NET MAUI Community Toolkit GitHub repository.