Create a Behavior for Calendar in a WPF UserControl to Select and Unselect dates with one click

Question

Hi to everyone,
I am developing an application with a WPF Client. This Client use the MVVM pattern.
In an UserControl the application must show some Calendars, so the user can select one or multiple dates.
For that use, I should implement some behavior that allows the user click once in a date and that date is selected (what already exists in .NET Framework) and with another click in the same date, that date is now unselected.
I've already made some searches and can't find anything useful.
This kind of behavior it is possible to implement in the Calendar Control? How exactly I do this?
Thanks for reading/helping
Rafael Duarte

Answer 1

You should be able to accomplish this by modifying the default template of the CalendarDayButtonStyle of the Calendar and handling the PreviewMouseLeftButtonDown of the Grid in the default template. Here is an example:
<Window.Resources>
<Style x:Key="CalendarDayButtonStyle1" TargetType="{x:Type CalendarDayButton}">
<Setter Property="MinWidth" Value="5"/>
<Setter Property="MinHeight" Value="5"/>
<Setter Property="FontSize" Value="10"/>
<Setter Property="HorizontalContentAlignment" Value="Center"/>
<Setter Property="VerticalContentAlignment" Value="Center"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type CalendarDayButton}">
<Grid Background="Transparent" PreviewMouseLeftButtonDown="Grid_PreviewMouseLeftButtonDown">
<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="#FF45D6FA" Visibility="Collapsed"/>
</Grid>
<ControlTemplate.Triggers>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="True"/>
<Condition Property="IsFocused" Value="True"/>
</MultiTrigger.Conditions>
<Setter Property="Visibility" TargetName="DayButtonFocusVisual" Value="Visible"/>
</MultiTrigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<Calendar x:Name="cal" CalendarDayButtonStyle="{DynamicResource CalendarDayButtonStyle1}" />
private void Grid_PreviewMouseLeftButtonDown(object sender, System.Windows.Input.MouseButtonEventArgs e) {
Grid grid = sender as Grid;
CalendarDayButton button = FindParent<CalendarDayButton>(grid);
if (button.IsSelected) {
Calendar cal = FindParent<Calendar>(button);
if (cal.SelectedDate.HasValue) {
cal.SelectedDates.Remove(cal.SelectedDate.Value);
e.Handled = true;
Hope that helps.
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