MathExpressionConverter

The MathExpressionConverter is a converter that allows users to perform various math operations. This works with a single Binding value, if you require multiple values through a MultiBinding then see MultiMathExpressionConverter

The Convert calculates the expression string defined in the ConverterParameter with one variable and returns a double result.

The value that is passed in to the converter will be named x. In order to refer to this value inside the expression you must use x (e.g. x / 2 will divide the incoming value by 2). Any other variable names in the expression will be ignored.

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 show how to add a Label that will show the result of x / 2 where x will have the value of 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 MathExpressionConverter

The MathExpressionConverter 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.MathExpressionConverterPage">

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

    <Label Text="{Binding MyValue, Converter={StaticResource MathExpressionConverter}, ConverterParameter='x/2'}" />

</ContentPage>

C#

The MathExpressionConverter can be used as follows in C#:

class MathExpressionConverterPage : ContentPage
{
    public MathExpressionConverterPage()
    {
        var label = new Label();

        label.SetBinding(
            Label.TextProperty,
            new Binding(
                static (ViewModels vm) => vm.MyValue,
                converter: new MathExpressionConverter(),
                converterParameter: "x/2"));

        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 MathExpressionConverterPage : ContentPage
{
    public MathExpressionConverterPage()
    {
        Content = new Label()
            .Bind(
                Label.TextProperty,
                static (ViewModel vm) => vm.MyValue,
                converter: new MathExpressionConverter(),
                converterParameter: "x/2");
    }
}

Supported operations

The following operations are supported:

• "+"
• "-"
• "*"
• "/"
• "%"
• "abs"
• "acos"
• "asin"
• "atan"
• "atan2"
• "ceiling"
• "cos"
• "cosh"
• "exp"
• "floor"
• "ieeeremainder"
• "log"
• "log10"
• "max"
• "min"
• "pow"
• "round"
• "sign"
• "sin"
• "sinh"
• "sqrt"
• "tan"
• "tanh"
• "truncate"
• "^"
• "pi"
• "e"

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