How to change Color define in Xaml Resources in code (UWP)

Question

[UWP]

I have many grids with color binding from App.xaml

MainPage.xaml ...

        <Grid
            Height="45"
            Margin="0,0,0,10"
            Background="{ThemeResource MyColor}">

App.xaml

<Application
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    RequestedTheme="Dark">
    <Application.Resources>
        <ResourceDictionary>
            <SolidColorBrush x:Key="MyColor">#FFFFFF</SolidColorBrush>

Then I want to change all of its, in code like this

    Application.Current.Resources["MyColor"] = new SolidColorBrush(Windows.UI.Color.FromArgb(255, 242, 101, 34));

But it not work. May I miss something? When I navigate to another page and navigate back, above code throw a System.Exception

Answer 1

StaticResource and ThemeResource doesn't support dynamic change as you try like DynamicResource in WPF. BTW if you reload the view like navigating back and forward you can see the changes but this is not a good solution.

Other hand, you can achieve some dynamic change with ThemeResource and change eg. colors depend on the current theme (Dark, Light, High Contrast)

Futher reading: https://docs.microsoft.com/en-us/windows/uwp/controls-and-patterns/xaml-theme-resources

Answer 2

If you know it's a SolidColorBrush then modify the Color property directly.

var brush = (SolidColorBrush)Application.Current.Resources["MyColor"];
brush.Color = Windows.UI.Color.FromArgb(255, 242, 101, 34);

You can't change the resources, but you can modify their properties if you have access.

Answer 3

I did it in the following way:

App.xaml

<Application
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    RequestedTheme="Dark">
<Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.ThemeDictionaries>
            <ResourceDictionary x:Key="Dark">
                <Color x:Key="UserAccentColor">#FFFFA500</Color>
                <SolidColorBrush x:Key="UserAccentBrush" Color="{StaticResource UserAccentColor}"/>
            </ResourceDictionary>
            <ResourceDictionary x:Key="Light">
                <Color x:Key="UserAccentColor">#FFFFA500</Color>
                <SolidColorBrush x:Key="UserAccentBrush" Color="{StaticResource UserAccentColor}"/>
            </ResourceDictionary>

Change color:

foreach (var dict in App.Current.Resources.ThemeDictionaries)
{
    var theme = dict.Value as Windows.UI.Xaml.ResourceDictionary;
    ((SolidColorBrush)theme["UserAccentBrush"]).Color = color;
}

Answer 4

(App.Current.Resources["MyColor"] as SolidColorBrush).Color = Windows.UI.Color.FromArgb(255, 242, 101, 34);