Using a ResourceDictionary Theme

Oct 13, 2025 by miodeya.com 49 views

Introduction

When developing a .NET 9.0 MAUI app, setting the background color of the entire application can be a crucial aspect of its design and user experience. In this article, we will explore the different methods of setting the background color of a MAUI app, including using a ResourceDictionary Theme and applying it in the App.xaml file.

Using a ResourceDictionary Theme

One of the most common methods of setting the background color of a MAUI app is by using a ResourceDictionary Theme. This approach involves creating a ResourceDictionary that contains the desired background color and then merging it into the App.xaml file.

Here's an example of how to create a ResourceDictionary Theme:

&lt;ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
&amp;lt;Color x:Key=&quot;BackgroundColor&quot;&amp;gt;#FF0000&amp;lt;/Color&amp;gt;

&lt;/ResourceDictionary&gt;

In this example, we have created a ResourceDictionary that contains a Color resource named "BackgroundColor" with a value of #FF0000, which is a bright red color.

To apply this ResourceDictionary to the App.xaml file, we can use the MergedDictionaries property:

&lt;Application xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:MauiApp1"
              x:Class="MauiApp1.App"&gt;
&amp;lt;Application.Resources&amp;gt;

    &amp;lt;ResourceDictionary.MergedDictionaries&amp;gt;

        &amp;lt;ResourceDictionary Source=&quot;Themes/Theme1.xaml&quot; /&amp;gt;

    &amp;lt;/ResourceDictionary.MergedDictionaries&amp;gt;

&amp;lt;/Application.Resources&amp;gt;

&lt;/Application&gt;

In this example, we have merged the ResourceDictionary Theme into the App.xaml file using the MergedDictionaries property.

However, this approach may not work as expected, especially when it comes to setting the background color of the entire application. This is because the ResourceDictionary Theme is only applied to the resources that are defined within it, and not to the entire application.

Using the `OnPlatform` Property

Another method of setting the background color of a MAUI app is by using the OnPlatform property. This property allows us to define different values for a property based on the platform that the app is running on.

Here's an example of how to use the OnPlatform property to set the background color of a MAUI app:

&lt;ContentPage xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:MauiApp1"
              x:Class="MauiApp1.MainPage"&gt;
&amp;lt;ContentPage.Background&amp;gt;

    &amp;lt;OnPlatform x:TypeArguments=&quot;Brush&quot;&amp;gt;

        &amp;lt;OnPlatform.iOS&amp;gt;

            &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

        &amp;lt;/OnPlatform.iOS&amp;gt;

        &amp;lt;OnPlatform.Android&amp;gt;

            &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

        &amp;lt;/OnPlatform.Android&amp;gt;

        &amp;lt;OnPlatform.WinUI&amp;gt;

            &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

        &amp;lt;/OnPlatform.WinUI&amp;gt;

    &amp;lt;/OnPlatform&amp;gt;

&amp;lt;/ContentPage.Background&amp;gt;

&lt;/ContentPage&gt;

In this example, we have used the OnPlatform property to define different background colors for each platform that the app is running on.

However, this approach may not be the most efficient way to set the background color of a MAUI app, especially when it comes to setting the background color of the entire application.

Using the `AppShell` Property

One of the most efficient ways to set the background color of a MAUI app is by using the AppShell property. This property allows us to define the background color of the entire application in a single place.

Here's an example of how to use the AppShell property to set the background color of a MAUI app:

&lt;Shell xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
       xmlns:local="clr-namespace:MauiApp1"
       x:Class="MauiApp1.AppShell"&gt;
&amp;lt;Shell.Background&amp;gt;

    &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

&amp;lt;/Shell.Background&amp;gt;

&lt;/Shell&gt;

In this example, we have used the AppShell property to set the background color of the entire application to a bright red color.

Conclusion

In conclusion, setting the background color of a .NET 9.0 MAUI app can be a crucial aspect of its design and user experience. In this article, we have explored the different methods of setting the background color of a MAUI app, including using a ResourceDictionary Theme, the OnPlatform property, and the AppShell property.

Each of these methods has its own advantages and disadvantages, and the choice of which method to use will depend on the specific requirements of the app.

By following the examples and code snippets provided in this article, developers can easily set the background color of their MAUI app and create a visually appealing and user-friendly experience for their users.

Additional Resources

For more information on setting the background color of a MAUI app, please refer to the following resources:

Q: What is the best way to set the background color of a MAUI app?

A: The best way to set the background color of a MAUI app is by using the AppShell property. This property allows you to define the background color of the entire application in a single place.

Q: How do I use the `AppShell` property to set the background color of a MAUI app?

A: To use the AppShell property to set the background color of a MAUI app, you can add the following code to your AppShell.xaml file:

&lt;Shell xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
       xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
       xmlns:local="clr-namespace:MauiApp1"
       x:Class="MauiApp1.AppShell"&gt;
&amp;lt;Shell.Background&amp;gt;

    &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

&amp;lt;/Shell.Background&amp;gt;

&lt;/Shell&gt;

In this example, we have set the background color of the entire application to a bright red color.

Q: Can I use a ResourceDictionary Theme to set the background color of a MAUI app?

A: Yes, you can use a ResourceDictionary Theme to set the background color of a MAUI app. However, this approach may not work as expected, especially when it comes to setting the background color of the entire application.

Q: How do I create a ResourceDictionary Theme to set the background color of a MAUI app?

A: To create a ResourceDictionary Theme to set the background color of a MAUI app, you can add the following code to your Themes folder:

&lt;ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"&gt;
&amp;lt;Color x:Key=&quot;BackgroundColor&quot;&amp;gt;#FF0000&amp;lt;/Color&amp;gt;

&lt;/ResourceDictionary&gt;

In this example, we have created a ResourceDictionary that contains a Color resource named "BackgroundColor" with a value of #FF0000, which is a bright red color.

Q: How do I apply a ResourceDictionary Theme to the App.xaml file of a MAUI app?

A: To apply a ResourceDictionary Theme to the App.xaml file of a MAUI app, you can add the following code to your App.xaml file:

&lt;Application xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:MauiApp1"
              x:Class="MauiApp1.App"&gt;
&amp;lt;Application.Resources&amp;gt;

    &amp;lt;ResourceDictionary.MergedDictionaries&amp;gt;

        &amp;lt;ResourceDictionary Source=&quot;Themes/Theme1.xaml&quot; /&amp;gt;

    &amp;lt;/ResourceDictionary.MergedDictionaries&amp;gt;

&amp;lt;/Application.Resources&amp;gt;

&lt;/Application&gt;

In this example, we have merged the ResourceDictionary Theme into the App.xaml file using the MergedDictionaries property.

Q: Can I use the `OnPlatform` property to set the background color of a MAUI app?

A: Yes, you can use the OnPlatform property to set the background color of a MAUI app. However, this approach may not be the most efficient way to set the background color of a MAUI app, especially when it comes to setting the background color of the entire application.

Q: How do I use the `OnPlatform` property to set the background color of a MAUI app?

A: To use the OnPlatform property to set the background color of a MAUI app, you can add the following code to your ContentPage.xaml file:

&lt;ContentPage xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:local="clr-namespace:MauiApp1"
              x:Class="MauiApp1.MainPage"&gt;
&amp;lt;ContentPage.Background&amp;gt;

    &amp;lt;OnPlatform x:TypeArguments=&quot;Brush&quot;&amp;gt;

        &amp;lt;OnPlatform.iOS&amp;gt;

            &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

        &amp;lt;/OnPlatform.iOS&amp;gt;

        &amp;lt;OnPlatform.Android&amp;gt;

            &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

        &amp;lt;/OnPlatform.Android&amp;gt;

        &amp;lt;OnPlatform.WinUI&amp;gt;

            &amp;lt;SolidColorBrush Color=&quot;#FF0000&quot; /&amp;gt;

        &amp;lt;/OnPlatform.WinUI&amp;gt;

    &amp;lt;/OnPlatform&amp;gt;

&amp;lt;/ContentPage.Background&amp;gt;

&lt;/ContentPage&gt;

In this example, we have used the OnPlatform property to define different background colors for each platform that the app is running on.

Conclusion

In conclusion, setting the background color of a .NET 9.0 MAUI app can be a crucial aspect of its design and user experience. By using the AppShell property, ResourceDictionary Theme, and OnPlatform property, developers can easily set the background color of their MAUI app and create a visually appealing and user-friendly experience for their users.

Additional Resources

For more information on setting the background color of a MAUI app, please refer to the following resources:

By following these resources, developers can gain a deeper understanding of the different methods of setting the background color of a MAUI app and create a more visually appealing and user-friendly experience for their users.