c# - How to conditionally use the 'default' color in MAUI? - Stack Overflow

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I'm looking for a way to get the default color in MAUI so that I can respect system themes/etc. I have a field that I want to change color under certain conditions, but remain the "default" color, platform-independent, if not. I'm currently using the .NET MAUI MVVM Toolkit, so I have a converter defined as follows:

    <ContentPage.Resources>
        <x:Double x:Key="Threshold">0</x:Double>
        <Color x:Key="FalseColor">DarkRed</Color>
        <!--What goes in here?-->
        <Color x:Key="TrueColor"></Color>
        <toolkit:CompareConverter x:Key="isAboveThresholdConverter" 
                ComparisonOperator="Greater"
                ComparingValue="{StaticResource Key=Threshold}"
                TrueObject="{StaticResource TrueColor}"
                FalseObject="{StaticResource FalseColor}"/>
    </ContentPage.Resources>

which is used here:

    <Label Text="{Binding RunningTotal}" TextColor="{Binding RunningTotal, Converter={StaticResource isAboveThresholdConverter}}"  Grid.Row="2" Grid.Column="2"/>

How do I get this to be DarkRed if the condition is false, but set the text color to whatever the system default color for text is if true?

I have tried:

• Leaving the TrueColor empty, as show in the example above
• Writing null for TrueColor in XAML
• Writing Default for TrueColor in XAML
• Searching MAUI docs for a Color.Default field (I am unsure such a field exists, though apparently it did in WinUI3, and there's some workaround work that was done but I do not understand the specific commit history)

I would like to avoid:

• Hardcoding Black and White as colors in the theme, since I'm only reasonably sure that those are the correct colors for text in the respective light/dark modes across all platforms and I want to do as little custom color work as possible.
• Coding an individual color per platform (see How can I use Windows/Android accent color in .NET Maui? for an example of how to get the accent color for specifically Windows, with an Android solution in the commments)

Is there a way to respect system default color regardless of platform, or am I out of luck?

I'm looking for a way to get the default color in MAUI so that I can respect system themes/etc. I have a field that I want to change color under certain conditions, but remain the "default" color, platform-independent, if not. I'm currently using the .NET MAUI MVVM Toolkit, so I have a converter defined as follows:

    <ContentPage.Resources>
        <x:Double x:Key="Threshold">0</x:Double>
        <Color x:Key="FalseColor">DarkRed</Color>
        <!--What goes in here?-->
        <Color x:Key="TrueColor"></Color>
        <toolkit:CompareConverter x:Key="isAboveThresholdConverter" 
                ComparisonOperator="Greater"
                ComparingValue="{StaticResource Key=Threshold}"
                TrueObject="{StaticResource TrueColor}"
                FalseObject="{StaticResource FalseColor}"/>
    </ContentPage.Resources>

which is used here:

    <Label Text="{Binding RunningTotal}" TextColor="{Binding RunningTotal, Converter={StaticResource isAboveThresholdConverter}}"  Grid.Row="2" Grid.Column="2"/>

How do I get this to be DarkRed if the condition is false, but set the text color to whatever the system default color for text is if true?

I have tried:

• Leaving the TrueColor empty, as show in the example above
• Writing null for TrueColor in XAML
• Writing Default for TrueColor in XAML
• Searching MAUI docs for a Color.Default field (I am unsure such a field exists, though apparently it did in WinUI3, and there's some workaround work that was done but I do not understand the specific commit history)

I would like to avoid:

• Hardcoding Black and White as colors in the theme, since I'm only reasonably sure that those are the correct colors for text in the respective light/dark modes across all platforms and I want to do as little custom color work as possible.
• Coding an individual color per platform (see How can I use Windows/Android accent color in .NET Maui? for an example of how to get the accent color for specifically Windows, with an Android solution in the commments)

Is there a way to respect system default color regardless of platform, or am I out of luck?

• c#
• maui

Share Follow edited Nov 21, 2024 at 0:51 WithoutAnAce asked Nov 19, 2024 at 20:27 WithoutAnAceWithoutAnAce 5566 bronze badges 4

• 1 Coding an individual color per platform (see How can I use Windows/Android accent color in .NET Maui? for an example of how to get the accent color for specifically Windows, with an Android solution in the commments) - I hope you are aware this is not the system Color that you get here but the Color set in the theme that you have for your MAUI app which is either the default that the MAUI team has created or the custom theme you created (if you have) per platform – FreakyAli Commented Nov 20, 2024 at 10:38
• 1 Hardcoding Black and White as colors in the theme, since I'm only reasonably sure that those are the correct colors for text in the respective light/dark modes across all platforms and I want to do as little custom color work as possible. As far as I know you don't get a default color for each theme from the Platform, even in the platform there are conditional themes that are created behind the scenes that update this color for you, but its not "Platform default" – FreakyAli Commented Nov 20, 2024 at 10:39
• These are both useful to know, and I'm glad I've found a real solution rather than either of these, since it sounds like neither would work the way I want – WithoutAnAce Commented Nov 20, 2024 at 14:50
• Your question was actually a bit vague, all you wanted was a default theme, instead your question sounded as if you wanted the system default from each os to be available to you – FreakyAli Commented Nov 20, 2024 at 15:41

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1 Answer 1

Sorted by: Reset to default 2

To get a default color, I suppose you can put a default label in the resource dictionary, e.g.

<Label x:Key="DefaultLabel"/>

Then you can refer to its color via {Binding TextColor, Source={StaticResource DefaultLabel}}

Also, you can use MultiMathExpressionConverter in a DataTrigger as follows:

<!-- Pseudo code - may contain syntax errors, default TrueColor is inferred -->
<Label Text="{Binding RunningTotal}" >
    <Label.Triggers>
         <DataTrigger TargetType="Label"
                      Binding="{MultiBinding {Binding RunningTotal},
                                             {Binding Source={StaticResource Threshold}},
                                             Converter={StaticResource MultiMathExpressionConverter},
                                             ConverterParameter='sign(x - x1)'}"
                      Value="-1">
             <Setter Property="TextColor" Value="{StaticResource FalseColor}" />
         </DataTrigger>
    </Label.Triggers>
</Label>

I have a `MultiMathExpressionConverter` enhancement to support boolean and comparison operators. It would help me a lot if you vote on the issue and the corresponding PR:

• Proposal Issue: https://github/CommunityToolkit/Maui/issues/2181
• Proposal PR https://github/CommunityToolkit/Maui/pull/2182

You can also solve this problem using boolean operators with the MultiMathExpressionConverter. Note these operators may need to use XAML friendly equivalents:

Operator	XAML	XAML friendly
&&	&&	and
||	||	or
>=	>=	ge
>	>	gt
<=	&lt;=	le
<	&lt;	lt

<Label Text="{Binding RunningTotal}"
       TextColor="{MultiBinding {Binding RunningTotal},
                                {Binding Source={StaticResource Threshold}},
                                {Binding TextColor, Source={StaticResource DefaultLabel}},
                                {Binding Source={StaticResource FalseColor}},
                                Converter={StaticResource MultiMathExpressionConverter},
                                ConverterParameter='x gt x1 ? x2 : x3'}" />

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