Button to change background colour - xaml

Question

I'm developing a UWP app. I would like to have a radio button change the background of the mainpage and settings page when clicked. The radio button code below is in Settings.xaml.cs
private void BGRadioButtonGreen_Checked(object sender, RoutedEventArgs e)
{
MainPage.Background = Brushes.Red??;
}
In this example I'm trying to select a radio button and have it change the settings and mainpage background to Green.However it doesn't seem to be working. Thanks in advance

Answer 1

You can do it be setting background color of root grid. Like in example below, after radio button checked color would change to red. This should be what you're looking for.
<Page
x:Class="Test.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Test"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" Background="Blue">
<Grid x:Name="MainGrid" Background="Green">
<StackPanel>
<RadioButton Content="Red" Tag="Green" Checked="RadioButton_Checked"/>
</StackPanel>
</Grid>
private void RadioButton_Checked(object sender, RoutedEventArgs e)
{
MainGrid.Background = new SolidColorBrush(Windows.UI.Colors.Red);
}

Answer 2

For changing background color, as #ColdMorningLight mentioned, you should set a SolidColorBrush value to the Background property.
Since you attempt to change the MainPage background color from Settings page, which is in different pages, you also need to get the current MainPage instance firstly and then set the page's background. For example:
MainPage mainPage;
public SettingPage()
{
this.InitializeComponent();
mainPage = (Window.Current.Content as Frame).Content as MainPage;
}
private void radchangecolor_Checked(object sender, RoutedEventArgs e)
{
mainPage.Background = new SolidColorBrush(Windows.UI.Colors.Green);
}
Pay attention that I set the page's background color, you only can see the effects when the root panel background color is transparent (the default value is Background="{ThemeResource ApplicationPageBackgroundThemeBrush}" ). Otherwise you need to change the root panel background color. For example, MainPage as follows will take effects:
<Page
...
mc:Ignorable="d" >
<StackPanel>
<Frame x:Name="frame" Height="200" Width="300" Background="Azure"></Frame>
<Button x:Name="btntest" Click="btntest_Click" Content="test"></Button>
</StackPanel>
</Page>