Background does not change of button C# WPF

Question

I am trying to change style on mouseover.

My Code is:

<Button Name="register" Content="Register" Margin="15,410,20,0" Padding="6" FontSize="18" VerticalAlignment="Top" Background="#FF0090D6" BorderBrush="#FF0090D6" Foreground="White">
                    <Button.Style>
                        <Style TargetType="Button">
                            <Style.Triggers>
                                <Trigger Property="IsMouseOver" Value="True">
                                    <Setter Property="Background" Value="Red"></Setter>
                                </Trigger>
                            </Style.Triggers>
                        </Style>
                    </Button.Style>
                </Button>

But the Background is the same default thing. But when i change property to BorderThickness then it works.

What am i doing wrong?

Answer 1

In the default template of button, there is trigger in ControlTemplate which set Background of button to #FFBEE6FD and since control template triggers have higher precedence compared to Style triggers that's why your trigger never works.

For that to achieve you have to override default template of button and remove that trigger from it so that your style trigger gets applied.

Here is the default template with that specific trigger commented out. In case you want to override BorderBrush as well, get rid of it as well from the template.

<ControlTemplate x:Key="DefaultTemplateOfButton" TargetType="ButtonBase">
    <Border BorderThickness="{TemplateBinding Border.BorderThickness}"
                BorderBrush="{TemplateBinding Border.BorderBrush}"
                Background="{TemplateBinding Panel.Background}"
                Name="border"
                SnapsToDevicePixels="True">
        <ContentPresenter RecognizesAccessKey="True"
                                Content="{TemplateBinding ContentControl.Content}"
                                ContentTemplate="{TemplateBinding ContentControl.ContentTemplate}"
                                ContentStringFormat="{TemplateBinding ContentControl.ContentStringFormat}"
                                Name="contentPresenter"
                                Margin="{TemplateBinding Control.Padding}"
                                HorizontalAlignment="{TemplateBinding Control.HorizontalContentAlignment}"
                                VerticalAlignment="{TemplateBinding Control.VerticalContentAlignment}"
                                SnapsToDevicePixels="{TemplateBinding UIElement.SnapsToDevicePixels}"
                                Focusable="False" />
    </Border>
    <ControlTemplate.Triggers>
        <Trigger Property="Button.IsDefaulted" Value="True">
            <Setter Property="Border.BorderBrush" TargetName="border">
                <Setter.Value>
                    <DynamicResource ResourceKey="{x:Static SystemColors.HighlightBrushKey}" />
                </Setter.Value>
            </Setter>
        </Trigger>
        <Trigger Property="UIElement.IsMouseOver" Value="True">
            <!--<Setter Property="Panel.Background" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FFBEE6FD</SolidColorBrush>
                </Setter.Value>
            </Setter>-->
            <Setter Property="Border.BorderBrush" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FF3C7FB1</SolidColorBrush>
                </Setter.Value>
            </Setter>
        </Trigger>
        <Trigger Property="ButtonBase.IsPressed" Value="True">
            <Setter Property="Panel.Background" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FFC4E5F6</SolidColorBrush>
                </Setter.Value>
            </Setter>
            <Setter Property="Border.BorderBrush" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FF2C628B</SolidColorBrush>
                </Setter.Value>
            </Setter>
        </Trigger>
        <Trigger Property="ToggleButton.IsChecked" Value="True">
            <Setter Property="Panel.Background" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FFBCDDEE</SolidColorBrush>
                </Setter.Value>
            </Setter>
            <Setter Property="Border.BorderBrush" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FF245A83</SolidColorBrush>
                </Setter.Value>
            </Setter>
        </Trigger>
        <Trigger Property="UIElement.IsEnabled" Value="False">
            <Setter Property="Panel.Background" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FFF4F4F4</SolidColorBrush>
                </Setter.Value>
            </Setter>
            <Setter Property="Border.BorderBrush" TargetName="border">
                <Setter.Value>
                    <SolidColorBrush>#FFADB2B5</SolidColorBrush>
                </Setter.Value>
            </Setter>
            <Setter Property="TextElement.Foreground" TargetName="contentPresenter">
                <Setter.Value>
                    <SolidColorBrush>#FF838383</SolidColorBrush>
                </Setter.Value>
            </Setter>
        </Trigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

---

How to set the control template to button?

Define the template somewhere under resource section of parent panel or UserControl and can be applied via StaticResource:

<Grid>
   <Grid.Resources>
      <ControlTemplate x:Key="MyTemplate"
                       TargetType="ButtonBase">
       .......
   </Grid.Resources>
   <Button Name="register" Template="{StaticResource MyTemplate}"...>
</Grid>

Answer 2

Edit: As Rohit pointed out in the comments,

This won't work on Windows 8 because of some changes in PresentationFramework where default template of button is declared. ... In Windows 7 default template of button doesn't have that ControlTemplate trigger. That's why your posted code works fine on Windows7 but it won't work on Windows 8 and higher.

---

Rohit's answer about DependencyProperty Precedence being the cause is correct, but there's a much simpler way of fixing it than overwriting the Button's Template.

If you review the DependencyProperty Precedence List, you'll notice that properties set in the <Tag> have a higher precedence than Triggered properties, which is why your button will always use the background you have defined in your <Button> tag.

If you move the Background property to the <Style> itself, then triggered property will work since Triggered properties take precedence over properties defined in a Style.

<Button Name="register" Content="Register" ...>
    <Button.Style>
        <Style TargetType="Button">
            <Setter Property="Background" Value="#FF0090D6" />
            <Style.Triggers>
                <Trigger Property="IsMouseOver" Value="True">
                    <Setter Property="Background" Value="Red" />
                </Trigger>
            </Style.Triggers>
        </Style>
    </Button.Style>
</Button>

Answer 3

You have to override the default template for achieve this.

  <Button Content="Button" HorizontalAlignment="Left" VerticalAlignment="Bottom" Width="50" Height="50" HorizontalContentAlignment="Left" BorderBrush="{x:Null}" Foreground="{x:Null}" Margin="50,0,0,0">
            <Button.Style>
                <Style TargetType="{x:Type Button}">
                    <Setter Property="Background" Value="Green"/>
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type Button}">
                                <Border Background="{TemplateBinding Background}">
                                    <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
                                </Border>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                    <Style.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Background" Value="DarkGoldenrod"/>
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </Button.Style>
        </Button>

Hope this helps.

Answer 4

 <Button Content="Button" HorizontalAlignment="Left" VerticalAlignment="Bottom" Width="50" Height="50" HorizontalContentAlignment="Left" BorderBrush="{x:Null}" Foreground="{x:Null}" Margin="50,0,0,0">
            <Button.Style>
                <Style TargetType="{x:Type Button}">
                    <Setter Property="Background" Value="Green"/>
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type Button}">
                                <Border Background="{TemplateBinding Background}">
                                    <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
                                </Border>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                    <Style.Triggers>
                        <Trigger Property="IsMouseOver" Value="True">
                            <Setter Property="Background" Value="DarkGoldenrod"/>
                        </Trigger>
                    </Style.Triggers>
                </Style>
            </Button.Style>
        </Button>

Above code perfectly works, Even with this user can change the background color of button in runtime/codebehind