C# WPF change BorderBrush inside the DatePicker

Question

I use a DatePicker for my application. I can change all the values I need. The last value that I need is the BorderBrush . I can't adjust the blue color shown here which is out of the standard. I have already created and edited a copy as CustomStyle. The theme of DatePicker seems relatively complex in WPF.

How can I set this color?

Maybe someone here can help me, thank you for your support. And yes, I have already read some topics about this theme here. But as it seems no suitable answer.

Answer 1

The Popup of a DatePicker is a Calendar and each day inside a Calendar is a CalendarDayButton .

For what you want to achieve you have to override the Style (more precisely the ControlTemplate ) of the CalendarDayButton .
The interesting part is the Rectangle "DayButtonFocusVisual"

<DatePicker>
    <DatePicker.CalendarStyle>
        <Style TargetType="{x:Type Calendar}">
            <Setter Property="CalendarDayButtonStyle">
                <Setter.Value>
                    <Style TargetType="{x:Type CalendarDayButton}">
                        <Setter Property="Template">
                                <Setter.Value>
                                    <ControlTemplate TargetType="{x:Type CalendarDayButton}">
                                        <Grid>
                                            <VisualStateManager.VisualStateGroups>
                                                <VisualStateGroup x:Name="CommonStates">
                                                    <VisualStateGroup.Transitions>
                                                        <VisualTransition GeneratedDuration="0:0:0.1"/>
                                                    </VisualStateGroup.Transitions>
                                                    <VisualState x:Name="Normal"/>
                                                    <VisualState x:Name="MouseOver">
                                                        <Storyboard>
                                                            <DoubleAnimation Duration="0" To="0.5" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="HighlightBackground"/>
                                                        </Storyboard>
                                                    </VisualState>
                                                    <VisualState x:Name="Pressed">
                                                        <Storyboard>
                                                            <DoubleAnimation Duration="0" To="0.5" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="HighlightBackground"/>
                                                        </Storyboard>
                                                    </VisualState>
                                                    <VisualState x:Name="Disabled">
                                                        <Storyboard>
                                                            <DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="HighlightBackground"/>
                                                            <DoubleAnimation Duration="0" To=".35" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="NormalText"/>
                                                        </Storyboard>
                                                    </VisualState>
                                                </VisualStateGroup>
                                                <VisualStateGroup x:Name="SelectionStates">
                                                    <VisualStateGroup.Transitions>
                                                        <VisualTransition GeneratedDuration="0"/>
                                                    </VisualStateGroup.Transitions>
                                                    <VisualState x:Name="Unselected"/>
                                                    <VisualState x:Name="Selected">
                                                        <Storyboard>
                                                            <DoubleAnimation Duration="0" To=".75" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="SelectedBackground"/>
                                                        </Storyboard>
                                                    </VisualState>
                                                </VisualStateGroup>
                                                <VisualStateGroup x:Name="CalendarButtonFocusStates">
                                                    <VisualStateGroup.Transitions>
                                                        <VisualTransition GeneratedDuration="0"/>
                                                    </VisualStateGroup.Transitions>
                                                    <VisualState x:Name="CalendarButtonFocused">
                                                        <Storyboard>
                                                            <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="DayButtonFocusVisual">
                                                                <DiscreteObjectKeyFrame KeyTime="0">
                                                                    <DiscreteObjectKeyFrame.Value>
                                                                        <Visibility>Visible</Visibility>
                                                                    </DiscreteObjectKeyFrame.Value>
                                                                </DiscreteObjectKeyFrame>
                                                            </ObjectAnimationUsingKeyFrames>
                                                        </Storyboard>
                                                    </VisualState>
                                                    <VisualState x:Name="CalendarButtonUnfocused">
                                                        <Storyboard>
                                                            <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="DayButtonFocusVisual">
                                                                <DiscreteObjectKeyFrame KeyTime="0">
                                                                    <DiscreteObjectKeyFrame.Value>
                                                                        <Visibility>Collapsed</Visibility>
                                                                    </DiscreteObjectKeyFrame.Value>
                                                                </DiscreteObjectKeyFrame>
                                                            </ObjectAnimationUsingKeyFrames>
                                                        </Storyboard>
                                                    </VisualState>
                                                </VisualStateGroup>
                                                <VisualStateGroup x:Name="ActiveStates">
                                                    <VisualStateGroup.Transitions>
                                                        <VisualTransition GeneratedDuration="0"/>
                                                    </VisualStateGroup.Transitions>
                                                    <VisualState x:Name="Active"/>
                                                    <VisualState x:Name="Inactive">
                                                        <Storyboard>
                                                            <ColorAnimation Duration="0" To="#FF777777" Storyboard.TargetProperty="(TextElement.Foreground).(SolidColorBrush.Color)" Storyboard.TargetName="NormalText"/>
                                                        </Storyboard>
                                                    </VisualState>
                                                </VisualStateGroup>
                                                <VisualStateGroup x:Name="DayStates">
                                                    <VisualStateGroup.Transitions>
                                                        <VisualTransition GeneratedDuration="0"/>
                                                    </VisualStateGroup.Transitions>
                                                    <VisualState x:Name="RegularDay"/>
                                                    <VisualState x:Name="Today">
                                                        <Storyboard>
                                                            <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="TodayBackground"/>
                                                            <ColorAnimation Duration="0" To="#FFFFFFFF" Storyboard.TargetProperty="(TextElement.Foreground).(SolidColorBrush.Color)" Storyboard.TargetName="NormalText"/>
                                                        </Storyboard>
                                                    </VisualState>
                                                </VisualStateGroup>
                                                <VisualStateGroup x:Name="BlackoutDayStates">
                                                    <VisualStateGroup.Transitions>
                                                        <VisualTransition GeneratedDuration="0"/>
                                                    </VisualStateGroup.Transitions>
                                                    <VisualState x:Name="NormalDay"/>
                                                    <VisualState x:Name="BlackoutDay">
                                                        <Storyboard>
                                                            <DoubleAnimation Duration="0" To=".2" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Blackout"/>
                                                        </Storyboard>
                                                    </VisualState>
                                                </VisualStateGroup>
                                            </VisualStateManager.VisualStateGroups>
                                            <Rectangle x:Name="TodayBackground" Fill="#FFAAAAAA" Opacity="0" RadiusY="1" RadiusX="1"/>
                                            <Rectangle x:Name="SelectedBackground" Fill="#FFBADDE9" Opacity="0" RadiusY="1" RadiusX="1"/>
                                            <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}"/>
                                            <Rectangle x:Name="HighlightBackground" Fill="#FFBADDE9" Opacity="0" RadiusY="1" RadiusX="1"/>
                                            <ContentPresenter x:Name="NormalText" TextElement.Foreground="#FF333333" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="5,1,5,1" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                                            <Path x:Name="Blackout" Data="M8.1772461,11.029181 L10.433105,11.029181 L11.700684,12.801641 L12.973633,11.029181 L15.191895,11.029181 L12.844727,13.999395 L15.21875,17.060919 L12.962891,17.060919 L11.673828,15.256231 L10.352539,17.060919 L8.1396484,17.060919 L10.519043,14.042364 z" Fill="#FF000000" HorizontalAlignment="Stretch" Margin="3" Opacity="0" RenderTransformOrigin="0.5,0.5" Stretch="Fill" VerticalAlignment="Stretch"/>
                                            <Rectangle x:Name="DayButtonFocusVisual" IsHitTestVisible="false" RadiusY="1" RadiusX="1" Stroke="Red" Visibility="Collapsed"/><!--Stroke="#FF45D6FA"-->
                                        </Grid>
                                    </ControlTemplate>
                                </Setter.Value>
                            </Setter>
                    </Style>
                </Setter.Value>
            </Setter>
        </Style>
    </DatePicker.CalendarStyle>
</DatePicker>