WPF - Customize the style of MessageBox in Extended WPF Toolkit
<p>For the sake of customization for MessageBox's style , I use this toolkit, and I copy the style code from its official page:</p>

<p><a href="http://wpftoolkit.codeplex.com/wikipage?title=MessageBox&amp;referringTitle=Documentation" rel="nofollow noreferrer">http://wpftoolkit.codeplex.com/wikipage?title=MessageBox&amp;referringTitle=Documentation</a></p>

<p>I changed it a bit: </p>

<pre><code>&lt;Application x:Class="TotaraEditor.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:TotaraEditor"
             xmlns:toolkit="http://schemas.xceed.com/wpf/xaml/toolkit"
             StartupUri="MainWindow.xaml"
             ShutdownMode="OnMainWindowClose"&gt;
    &lt;Application.Resources&gt;
        &lt;ResourceDictionary&gt;
            &lt;ResourceDictionary.MergedDictionaries&gt;
                &lt;ResourceDictionary Source="Themes/MetroDark/MetroDark.MSControls.Core.Implicit.xaml" /&gt;
                &lt;ResourceDictionary Source="Themes/MetroDark/MetroDark.MSControls.Toolkit.Implicit.xaml" /&gt;
            &lt;/ResourceDictionary.MergedDictionaries&gt;

            &lt;SolidColorBrush x:Key="MyButtonHoverBrush" Color="#FF2D2D30" /&gt;
            &lt;SolidColorBrush x:Key="MyButtonPressedBrush" Color="#FF03A9DD" /&gt;

            &lt;Style x:Key="MyCloseButtonStyle" TargetType="Button"&gt;
                &lt;Setter Property="Template"&gt;
                    &lt;Setter.Value&gt;
                        &lt;ControlTemplate TargetType="Button"&gt;
                            &lt;Grid&gt;
                                &lt;VisualStateManager.VisualStateGroups&gt;
                                    &lt;VisualStateGroup x:Name="CommonStates"&gt;
                                        &lt;VisualState x:Name="Normal"/&gt;
                                        &lt;VisualState x:Name="MouseOver"&gt;
                                            &lt;Storyboard&gt;
                                                &lt;ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="Background" Storyboard.TargetProperty="(Border.Background)"&gt;
                                                    &lt;DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{StaticResource MyButtonHoverBrush}"&gt;&lt;/DiscreteObjectKeyFrame&gt;
                                                &lt;/ObjectAnimationUsingKeyFrames&gt;
                                            &lt;/Storyboard&gt;
                                        &lt;/VisualState&gt;
                                        &lt;VisualState x:Name="Pressed"&gt;
                                            &lt;Storyboard&gt;
                                                &lt;ObjectAnimationUsingKeyFrames BeginTime="00:00:00" Duration="00:00:00.0010000" Storyboard.TargetName="Background" Storyboard.TargetProperty="(Border.Background)"&gt;
                                                    &lt;DiscreteObjectKeyFrame KeyTime="00:00:00" Value="{StaticResource MyButtonPressedBrush}"&gt;&lt;/DiscreteObjectKeyFrame&gt;
                                                &lt;/ObjectAnimationUsingKeyFrames&gt;
                                            &lt;/Storyboard&gt;
                                        &lt;/VisualState&gt;
                                    &lt;/VisualStateGroup&gt;
                                &lt;/VisualStateManager.VisualStateGroups&gt;
                                &lt;Border x:Name="Background" CornerRadius="0,0,0,0" Background="Green"&gt;
                                    &lt;Border Margin="1,0,1,1" BorderBrush="#59FFFFFF" BorderThickness="1" CornerRadius="0,0,1,0"/&gt;
                                &lt;/Border&gt;
                                &lt;ContentPresenter x:Name="contentPresenter" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" Content="{TemplateBinding Content}" ContentTemplate="{TemplateBinding ContentTemplate}"/&gt;
                                &lt;Path x:Name="path" Fill="White" Margin="0,0,0,1" Visibility="Collapsed"
                    Height="60"
        Width="7"
        Stretch="Fill"
        Opacity="1"
        Data="M 2,6 C2,6 3,6 3,6 3,6 3,5 3,5 3,5 4,5 4,5 4,5 4,6 4,6 4,6 5,6 5,6 5,6 7,6 7,6 7,6 7,5 7,5 7,5 6,5 6,5 6,5 6,4 6,4 6,4 5,4 5,4 5,4 5,2 5,2 5,2 6,2 6,2 6,2 6,1 6,1 6,1 7,1 7,1 7,1 7,0 7,0 7,0 5,0 5,0 5,0 4,0 4,0 4,0 4,1 4,1 4,1 3,1 3,1 3,1 3,0 3,0 3,0 2,0 2,0 2,0 0,0 0,0 0,0 0,1 0,1 0,1 1,1 1,1 1,1 1,2 1,2 1,2 2,2 2,2 2,2 2,4 2,4 2,4 1,4 1,4 1,4 1,5 1,5 1,5 0,5 0,5 0,5 0,6 0,6 0,6 2,6 2,6 z"/&gt;
                            &lt;/Grid&gt;
                        &lt;/ControlTemplate&gt;
                    &lt;/Setter.Value&gt;
                &lt;/Setter&gt;
            &lt;/Style&gt;

            &lt;Style TargetType="{x:Type toolkit:MessageBox}"&gt;
                &lt;Setter Property="Background" Value="#FF1E1E1E" /&gt;
                &lt;Setter Property="BorderBrush" Value="#FF999999" /&gt;
                &lt;Setter Property="CaptionForeground" Value="#FFF1F1F1" /&gt;
                &lt;Setter Property="WindowBorderBrush" Value="#FF686868" /&gt;
                &lt;Setter Property="WindowBackground" Value="#FF2D2D30" /&gt;
                &lt;Setter Property="WindowOpacity" Value="0.3" /&gt;
                &lt;Setter Property="Foreground" Value="#FFF1F1F1"/&gt;
                &lt;Setter Property="CloseButtonStyle" Value="{StaticResource MyCloseButtonStyle}"/&gt;
            &lt;/Style&gt;



        &lt;/ResourceDictionary&gt;

    &lt;/Application.Resources&gt;
&lt;/Application&gt;
</code></pre>

<p>This is how I use it in code behind:</p>

<pre><code>var res = Xceed.Wpf.Toolkit.MessageBox.Show( 
                            "R U sure?", 
                            "Confirm dialog", 
                            MessageBoxButton.YesNoCancel, 
                            MessageBoxImage.None, 
                            MessageBoxResult.Cancel, 
                            null 
                        ); 
if ("Cancel" == res.ToString()) {...} 
else if ("No" == res.ToString()) {...} 
else if ("Yes" == res.ToString()) {...} 
else {...}
</code></pre>

<p>And now what I have got is:
<a href="https://i.stack.imgur.com/b42Da.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/b42Da.png" alt="enter image description here"></a></p>

<p>As there is no way to touch the XAML of those buttons, how should I change the buttons style? At least I want to remove the glowing effect of the header.</p>

<p>Thanks.</p>

<p><strong>UPDATE</strong></p>

<p>I am sure the glowing effect is not caused by some style applied to the Label, it is a styled rectangle underneath the Label, I found this in WPF Inspector:</p>

<p><a href="https://i.stack.imgur.com/FxTnb.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FxTnb.png" alt="enter image description here"></a></p>

<p>After I set the height of that rect to 0, that glowing thing disappeared.</p>