How to Handle Key Events

Question

I have a DatePicker on a wpf window. When the user presses the plus or minus keys I want to capture that event and increment the date value of the control by one day and increment the display accordingly.

Here is what I've tried:

Private Sub dtpChargeDate_PreviewKeyUp(sender As Object, e As KeyEventArgs) Handles dtpChargeDate.PreviewKeyUp
        If e.Key = Key.Subtract OrElse e.Key = Key.OemMinus OrElse e.Key = Key.Add OrElse e.Key = Key.OemPlus Then
            e.Handled = True
            <Change the date ....>
        End If

I thought that setting e.Handled = True would prevent the key from affecting the display but it doesn't. I end up with plus or minus characters in the textbox of the DatePicker which messes up the date value. How can I capture the key presses before they are processed normally?

Answer 1

Hi
The DateTimePicker automatically responds to the arrow keys when a field is focused in the DateTimePicker text area, and increases/decreases the field accordingly - day month year.
I know you are asking for the +/- keys to do this, but seems overkill. Of course, you can do it that way too.

Answer 2

You can use the method at How to: Create a RoutedCommand :

            <DatePicker.CommandBindings>  
                <CommandBinding Command="{x:Static local:MainWindow.CustomRoutedCommand}"  
                    Executed="ExecutedCustomCommand"  
                    CanExecute="CanExecuteCustomCommand" />  
            </DatePicker.CommandBindings>  

when I test with Key.Subtract (added with CustomRoutedCommand.InputGestures.Add), the minus character is not displayed :

Answer 3

If you want to achieve previous/next day by -/+ keys, you could refer to the code below. If I misunderstood, please let me know.
MainWindow.xaml:

 <Grid>  
        <DatePicker Name="dpick" Width="200" Height="40" PreviewKeyDown="dpick_PreviewKeyDown" />  
    </Grid>  

MainWIndow.xaml.vb:

 Private Sub dpick_PreviewKeyDown(sender As Object, e As KeyEventArgs)  
        Dim dp = TryCast(sender, DatePicker)  
        If dp Is Nothing Then Return  
        If Not dp.SelectedDate.HasValue Then Return  
        Dim dayTime = dp.SelectedDate.Value  
        Select Case e.Key  
            Case Key.Add  
                e.Handled = True  
                MessageBox.Show("+ pressed")  
                dp.SetValue(DatePicker.SelectedDateProperty, dayTime.AddDays(1))  
            Case Key.Subtract  
                e.Handled = True  
                MessageBox.Show("- pressed")  
                dp.SetValue(DatePicker.SelectedDateProperty, dayTime.AddDays(-1))  
        End Select  
    End Sub  

The result:

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