How to change a WPF window backgroud with a data trigger? - wpf

Question

I want to change the background color of our apps main window when a property changes. We have a business date that can be changed and I want to change the window background when it has changed from expected. I've set up a property to tell this. But can I set a style datatrigger on a window that changes itself? Or would I need to do this in the app.xaml?

Answer 1

I ended up kind of doing what Drew suggested. Except I didn't use a Dependency Property.
<Window.Resources>
<SolidColorBrush x:Key="windowBGBrush" Color="Green"/>
<SolidColorBrush x:Key="windowBGBrushBusinessDateChanged" Color="Red"/>
</Window.Resources>
<Window.Style >
<Style TargetType="{x:Type Window}">
<Setter Property="Background" Value="{DynamicResource windowBGBrush}"/>
<Style.Triggers>
<DataTrigger Binding="{Binding IsBusinessDateChanged}" Value="true">
<Setter Property="Background" Value="{DynamicResource windowBGBrushBusinessDateChanged}"/>
</DataTrigger>
</Style.Triggers>
</Style>
</Window.Style>
IsBusinessDateChanged is a property on my Viewmodel that gets set by a service. I'm not sure why this was so hard.

Answer 2

If you're exposing a custom property on the Window just make sure it's defined as a DependencyProperty and then you should be able to use a regular trigger in the style to react to the property. Like so:
<Window.Style>
<Style TargetType="{x:Type MyWindow}">
<Style.Triggers>
<Trigger Property="MyProperty" Value="True">
<Setter Property="Background" Value="Red" />
</Trigger>
</Style.Triggers>
</Style>
</Window.Style>

Answer 3

Here's a solution with a converter approach:
XAML:
<Window x:Class="StackOverflowTests.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" x:Name="window1" Width="300"
xmlns:local="clr-namespace:StackOverflowTests">
<Window.Resources>
<local:DateToColorConverter x:Key="DateToColorConverter" />
</Window.Resources>
<Window.Background>
<SolidColorBrush Color="{Binding ElementName=textBoxName, Path=Text, Converter={StaticResource DateToColorConverter}}" />
</Window.Background>
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBox x:Name="textBoxName" Margin="5"></TextBox>
</Grid>
</Window>
C#:
using System;
using System.Windows;
using System.Windows.Data;
using System.Windows.Media;
namespace StackOverflowTests
{
/// <summary>
/// Interaction logic for Window1.xaml
/// </summary>
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
}
}
public class DateToColorConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
DateTime date;
if (DateTime.TryParse(value.ToString(), out date))
{
if (date == DateTime.Today)
return Colors.Green;
else
return Colors.Red;
}
else
{
return Colors.Gold;
}
}
public object ConvertBack(object value, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
throw new System.NotImplementedException();
}
#endregion
}
}

Answer 4

Maybe it's better to just bind the background with the property. You need to set the datasource of the window to the object and may need a valueconverter.