This is my XAML:
<xctk:DatePicker HorizontalAlignment="Left" Margin="144,50,0,0" VerticalAlignment="Top" Width="155" Name="ctlFrom" SelectedDate="{Binding Path=dtFrom, Mode=TwoWay}" ></xctk:DatePicker><xctk:DatePicker HorizontalAlignment="Left" Margin="144,88,0,0" VerticalAlignment="Top" Width="155" Name="ctlTo" SelectedDate="{Binding Path=dtTo, Mode=TwoWay}" ></xctk:DatePicker><Button Content="Start" HorizontalAlignment="Left" Margin="24,215,0,0" VerticalAlignment="Top" Width="75" Click="btnStart_Click" ><Button.Style><Style><Style.Triggers><MultiDataTrigger><MultiDataTrigger.Conditions><Condition Binding="{Binding SelectedDate, ElementName=ctlFrom, Converter={StaticResource NullToBoolConverter1}, UpdateSourceTrigger=PropertyChanged}" Value="True" /><Condition Binding="{Binding SelectedDate, ElementName=ctlTo, Converter={StaticResource NullToBoolConverter1}, UpdateSourceTrigger=PropertyChanged}" Value="True" /></MultiDataTrigger.Conditions><Setter Property="Button.IsEnabled" Value="True" /></MultiDataTrigger></Style.Triggers></Style></Button.Style></Button>
Currently, it doesn't block the button. I'd like to know how to lock the button if at leas one of these pickers is empty. How is this done only with XAML, i.e. with no additional coding?
