- A+
所属分类：.NET技术
背景
业务开发过程中遇到一个日期范围选择的需求，和Element UI的DateTimePicker组件比较类似，由两个日历控件组成，联动选择起始时间和结束时间。
问题
WPF中提供了一个DatePicker的控件，主要由DatePickerTextBox、Button和一个Calendar组成，其中Calendar是后台代码动态添加的，因此不能直接通过自定义DatePicker的控件模板实现需求。这里通过实现自定义DateTimePicker控件来满足需求。
技术要点与实现
由于Calendar结构比较复杂，本文通过控件组合的方式简单实现自定义DateTimePicker。先来看下实现效果。
首先创建一个名为DateTimePicker的UserControl,添加依赖属性HoverStart和HoverEnd用于控制日历中的开始日期和结束日期，添加依赖属性DateTimeRangeStart和DateTimeRangeEnd用于设置外部设置/获取起始时间和结束时间。
然后在XAML中添加两个WatermarkTextBox用于输入起始时间和结束时间（增加校验规则验证时间的合法性，这里不再详细说明如何写校验规则，具体可参考ValidationRule实现参数绑定）。接着添加一个Popup(默认关闭)，并在其中添加两个Calendar用于筛选日期，以及四个ComboBox用于筛选小时和分钟。当WatermarkTextBox捕获到鼠标时触发Popup打开。
<Grid> <Border Height="30" Width="320" BorderBrush="#c4c4c4" BorderThickness="1" CornerRadius="2"> <StackPanel x:Name="datetimeSelected" Orientation="Horizontal" Height="30"> <local:WatermarkTextBox x:Name="DateStartWTextBox" Style="{StaticResource DateWatermarkTextBoxStyle}" GotMouseCapture="WatermarkTextBox_GotMouseCapture"> <local:WatermarkTextBox.Resources> <helper:BindingProxy x:Key="dateRangeCeiling" Data="{Binding Text,ElementName=DateEndWTextBox}"/> </local:WatermarkTextBox.Resources> <local:WatermarkTextBox.Text> <Binding Path="DateTimeRangeStart" ElementName="self" StringFormat="{}{0:yyyy-MM-dd HH:mm}" UpdateSourceTrigger="PropertyChanged"> <Binding.ValidationRules> <helper:DateTimeValidationRule Type="Range"> <helper:ValidationParams Param1="{x:Static System:DateTime.Today}" Param2="{Binding Data,Source={StaticResource dateRangeCeiling}}"/> </helper:DateTimeValidationRule> </Binding.ValidationRules> </Binding> </local:WatermarkTextBox.Text> </local:WatermarkTextBox> <TextBlock Text="~"/> <local:WatermarkTextBox x:Name="DateEndWTextBox" Style="{StaticResource DateWatermarkTextBoxStyle}" GotMouseCapture="WatermarkTextBox_GotMouseCapture"> <local:WatermarkTextBox.Resources> <helper:BindingProxy x:Key="dateRangeFloor" Data="{Binding Text,ElementName=DateStartWTextBox}"/> </local:WatermarkTextBox.Resources> <local:WatermarkTextBox.Text> <Binding Path="DateTimeRangeEnd" ElementName="self" StringFormat="{}{0:yyyy-MM-dd HH:mm}" UpdateSourceTrigger="PropertyChanged"> <Binding.ValidationRules> <helper:DateTimeValidationRule Type="Floor"> <helper:ValidationParams Param1="{Binding Data,Source={StaticResource dateRangeFloor}}"/> </helper:DateTimeValidationRule> </Binding.ValidationRules> </Binding> </local:WatermarkTextBox.Text> </local:WatermarkTextBox> <local:ImageButton Width="18" Height="18" Click="ImageButton_Click" HoverImage="/LBD_CLP_WPFControl;component/Images/calendar_hover.png" NormalImage="/LBD_CLP_WPFControl;component/Images/calendar.png" /> </StackPanel> </Border> <Popup x:Name="DatetimePopup" AllowsTransparency="True" StaysOpen="False" Placement="Top" VerticalOffset="-10" HorizontalOffset="-300" PlacementTarget="{Binding ElementName=datetimeSelected}" PopupAnimation="Slide"> <Grid Background="White" Margin="3"> <Grid.Effect> <DropShadowEffect Color="Gray" BlurRadius="16" ShadowDepth="3" Opacity="0.2" Direction="0" /> </Grid.Effect> <Grid.RowDefinitions> <RowDefinition Height="*"/> <RowDefinition Height="42"/> <RowDefinition Height="42"/> </Grid.RowDefinitions> <StackPanel Orientation="Horizontal"> <Calendar x:Name="startCalendar" DockPanel.Dock="Left" Style="{DynamicResource CalendarStyle}" SelectionMode="SingleRange" SelectedDatesChanged="Calendar_SelectedDatesChanged"/> <Line Y1="0" Y2="{Binding ActualHeight ,ElementName=startCalendar}" Stroke="#e4e4e4"/> <Calendar x:Name="endCalendar" DockPanel.Dock="Right" Style="{DynamicResource CalendarStyle}" SelectionMode="SingleRange" SelectedDatesChanged="Calendar_SelectedDatesChanged" DisplayDate="{Binding DisplayDate,ElementName=startCalendar,Converter={StaticResource DateTimeAddtionConverter},ConverterParameter=1}"/> </StackPanel> <Border Grid.Row="1" BorderThickness="0 0 0 1" BorderBrush="#e4e4e4"> <StackPanel Orientation="Horizontal" TextElement.Foreground="#999999" TextElement.FontSize="14"> <TextBlock Text="开始时间:" Margin="15 0 7 0"/> <ComboBox x:Name="startHours" Width="64" ItemStringFormat="{}{0:D2}" SelectionChanged="startHours_SelectionChanged"/> <TextBlock Text=":" Margin="5 0 5 0"/> <ComboBox x:Name="startMins" ItemStringFormat="{}{0:D2}" Width="64"/> <TextBlock Text="截止时间:" Margin="40 0 7 0"/> <ComboBox x:Name="endHours" ItemStringFormat="{}{0:D2}" Width="64"/> <TextBlock Text=":" Margin="5 0 5 0"/> <ComboBox x:Name="endMins" ItemStringFormat="{}{0:D2}" Width="64"/> </StackPanel> </Border> <StackPanel Grid.Row="2" Orientation="Horizontal" HorizontalAlignment="Right" Margin="0 0 11 0"> <local:ImageButton x:Name="clearBtn" Style="{StaticResource ImageLinkButton}" Content="清空" FontSize="14" Foreground="#0099ff" Click="clearBtn_Click" NormalImage="{x:Null}" HoverImage="{x:Null}" DownImage="{x:Null}" /> <Button x:Name="yesBtn" Content="确定" Width="56" Height="28" Margin="12 0 0 0" Click="yesBtn_Click"> <Button.Style> <Style TargetType="{x:Type Button}" BasedOn="{StaticResource BaseButtonStyle}"> <Setter Property="BorderThickness" Value="1"/> <Setter Property="BorderBrush" Value="#dcdfe6"/> <Setter Property="Foreground" Value="#333333"/> <Setter Property="OverridesDefaultStyle" Value="True"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type Button}"> <Border x:Name="border" Background="Transparent" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3" ClipToBounds="True"> <ContentPresenter RecognizesAccessKey="True" Margin="{TemplateBinding Padding}" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/> </Border> <ControlTemplate.Triggers> <MultiTrigger> <MultiTrigger.Conditions> <Condition Property="IsPressed" Value="false"/> <Condition Property="IsMouseOver" Value="true"/> </MultiTrigger.Conditions> <Setter Property="BorderBrush" Value="#409eff"/> <Setter Property="Foreground" Value="#409eff"/> </MultiTrigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter> </Style> </Button.Style> </Button> </StackPanel> </Grid> </Popup> </Grid> 紧接着就是修改Calendar的样式了。通常情况下，自定义控件模板只需要在Visual Studio的设计窗口或者Blend中选中控件，然后右键菜单中编辑模板即可。可能由于Calendar中的部分元素（CalendarButton和CalendarDayButton）是后台代码生成，这个方法编辑Calendar模板副本生成的CalendarStyle不包含完整的可视化树结构，无法对样式进一步修改。幸运的是微软官方文档公开了控件的默认样式和模板，在此基础上进行修改即可。通过官方文档可以发现Calendar完整的可视化树中包含了四个类型控件Calendar、CalendarItem、CalendarButton、CalendarDayButton。其中CalendarDayButton对应的就是日历中具体的“天”，管理着具体的“天”的状态，比如选中状态、不可选状态等，这也是我们主要修改的地方，接下来看下CalendarDayButton的样式。（其他几个元素的样式和模板参照官方文档修改即可）
<Style x:Key="CalendarDayButtonStyle" TargetType="{x:Type CalendarDayButton}"> <Setter Property="MinWidth" Value="5" /> <Setter Property="MinHeight" Value="5" /> <Setter Property="Width" Value="42"/> <Setter Property="Height" Value="42"/> <Setter Property="FontSize" Value="12" /> <Setter Property="HorizontalContentAlignment" Value="Center" /> <Setter Property="VerticalContentAlignment" Value="Center" /> <Setter Property="BorderThickness" Value="0"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="{x:Type CalendarDayButton}"> <Grid Height="26" MouseUp="Grid_MouseUp"> <Border x:Name="SelectedBackground" Background="#f2f6fc" Visibility="Collapsed"> <Border.CornerRadius> <MultiBinding Converter="{StaticResource SelectedDatesConverter}"> <Binding/> <Binding Path="HoverStart" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/> <Binding Path="HoverEnd" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/> </MultiBinding> </Border.CornerRadius> </Border> <Grid Width="22" Height="22"> <Rectangle x:Name="StartStopBackground" Fill="#409eff" RadiusX="11" RadiusY="11" > <Rectangle.Visibility> <MultiBinding Converter="{StaticResource SelectedDatesConverter}"> <Binding/> <Binding Path="HoverStart" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/> <Binding Path="HoverEnd" RelativeSource="{RelativeSource AncestorType={x:Type local:DateTimePicker}}"/> <Binding Path="IsInactive" RelativeSource="{RelativeSource AncestorType={x:Type CalendarDayButton}}"/> </MultiBinding> </Rectangle.Visibility> </Rectangle> <Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" /> <Rectangle x:Name="HighlightBackground" Grid.ColumnSpan="2" Fill="#FFBADDE9" Opacity="0" RadiusX="11" RadiusY="11" /> <ContentPresenter x:Name="NormalText" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" TextElement.Foreground="#FF333333" /> <Path x:Name="Blackout" Grid.ColumnSpan="2" Margin="3" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" 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" Opacity="0" RenderTransformOrigin="0.5,0.5" Stretch="Fill" /> <Rectangle x:Name="DayButtonFocusVisual" Grid.ColumnSpan="2" IsHitTestVisible="false" RadiusX="11" RadiusY="1" Stroke="#FF45D6FA" Visibility="Collapsed" /> </Grid> </Grid> <ControlTemplate.Triggers> <Trigger Property="IsInactive" Value="True"> <Setter Property="Visibility" Value="Collapsed" TargetName="SelectedBackground"/> <Setter Property="TextElement.Foreground" Value="#c0c4cc" TargetName="NormalText"/> </Trigger> <Trigger Property="IsBlackedOut" Value="true"> <Setter Property="Visibility" Value="Collapsed" TargetName="SelectedBackground"/> <Setter Property="TextElement.Foreground" Value="#c0c4cc" TargetName="NormalText"/> </Trigger> <MultiTrigger> <MultiTrigger.Conditions> <Condition Property="IsInactive" Value="false"/> <Condition Property="IsSelected" Value="true"/> </MultiTrigger.Conditions> <MultiTrigger.Setters> <Setter Property="Visibility" Value="Visible" TargetName="SelectedBackground"/> </MultiTrigger.Setters> </MultiTrigger> <MultiTrigger> <MultiTrigger.Conditions> <Condition Property="IsInactive" Value="false"/> <Condition Property="IsBlackedOut" Value="false"/> <Condition Property="IsMouseOver" Value="true"/> </MultiTrigger.Conditions> <MultiTrigger.Setters> <Setter Property="Opacity" Value="0.5" TargetName="HighlightBackground"/> </MultiTrigger.Setters> </MultiTrigger> <MultiTrigger> <MultiTrigger.Conditions> <Condition Property="IsInactive" Value="false"/> <Condition Property="IsToday" Value="true"/> </MultiTrigger.Conditions> <MultiTrigger.Setters> <Setter Property="TextElement.Foreground" Value="#409eff" TargetName="NormalText"/> </MultiTrigger.Setters> </MultiTrigger> <MultiTrigger> <MultiTrigger.Conditions> <Condition Property="IsInactive" Value="false"/> <Condition Property="Visibility" Value="Visible" SourceName="StartStopBackground"/> </MultiTrigger.Conditions> <MultiTrigger.Setters> <Setter Property="TextElement.Foreground" Value="#ffffff" TargetName="NormalText"/> </MultiTrigger.Setters> </MultiTrigger> </ControlTemplate.Triggers> </ControlTemplate> </Setter.Value> </Setter> </Style> 样式中用到一个MultiBinding绑定CalendarDayButton以及前边提到的两个依赖属性：HoverStart和HoverEnd，然后通过MultiValueConverter转换器比较CalendarDayButton是否处于选中的日期范围，根据不同的状态设置其背景色和字体颜色。
最后就是在后台代码中根据日历的SelectedDatesChanged事件设置HoverStart和HoverEnd的值，以此来控制DateTimePicker中选中日期的样式。
总结
本文分享了一种简单实现自定义DateTimePicker控件的方式，同时也介绍了另外一种查看原生控件默认样式和模板的方法：查看微软官方文档。这种方法虽然不如在Visual Studio的设计窗口或者Blend中编辑模板副本方便，但提供了完整的结构、每个元素的组成部分以及可视化状态，方便开发人员清晰的了解控件全貌，可以应对修改复杂的原生控件样式和模板的需求。
