ColorToInverseColorConverter

Article
02/03/2023

The ColorToInverseColorConverter is a one way converter that allows users to convert an incoming Color to its inverse.

The Convert method returns the supplied value converted to its inverse.

The ConvertBack method is not supported.

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

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 ColorToInverseColorConverter

The ColorToInverseColorConverter 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. ColorToInverseColorConverterPage">

    <ContentPage.Resources>
        <ResourceDictionary>
            <toolkit:ColorToInverseColorConverter x:Key="ColorToInverseColorConverter" />
        </ResourceDictionary>
    </ContentPage.Resources>

    <Label Text="This Text is the inverse of the Background"
           TextColor="{Binding Source={RelativeSource AncestorType={x:Type ContentPage}}, Path=BackgroundColor, Converter={StaticResource ColorToInverseColorConverter}}" />

</ContentPage>

C#

The ColorToInverseColorConverter can be used as follows in C#:

class ColorToInverseColorConverterPage : ContentPage
{
    public ColorToInverseColorConverterPage()
    {
        var label = new Label { Text = "This Text is the inverse of the Background" };

        label.SetBinding(
            Label.TextColorProperty,
            new Binding(
                static (ContentPage page) => page.BackgroundColor,
                converter: new ColorToInverseColorConverter(),
                source: this));

        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 ColorToInverseColorConverterPage : ContentPage
{
    public ColorToInverseColorConverterPage()
    {
        Content = new Label { Text = "This Text is the inverse of the Background" }
            .Bind(
                Label.TextColorProperty,
                getter: static (ContentPage page) => page.BackgroundColor,
                converter: new ColorToInverseColorConverter(),
                source: this);
    }
}

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

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