I have handled SelectionChanged and MouseLeftButtonDown events on WPF listbox. I need to ensure that SelectionChanged event is fired before MouseLeftButtonDown event.
Though the events do occur in desired order but is there any way to enforce that?
Thanks
Related
I've created a WPF UserControl with some TextBoxes, but if I click into a TextBox on it, the OnGotFocus of the UserControl is not called.
How can I get it? Or what is the best practice in that situation?
The OnGotFocus method is fired in response to the GotFocus routed event that have the bubbling routing strategy. This method is not fired because the corresponding event is processed at the embedded child control level.
You can check GotFocus/LostFocus events. These event should be fired for your TextBox and UserControl as well.
When are these events raised, and how are they related? "CommandManager.CanExecute and CanExecute of CommandBinding???
The CanExecute event of a CommandBinding is fired when the CommandBinding believes something changed that could affect the state of the command. This is primarily when the user interacts with the UI in some way (mouse moves, clicks, focus changes, etc.), or when a user action causes a PropertyChanged or CollectionChanged event. This event does not get fired when your code changes something in the UI, or causes a PropertyChanged event to fire.
Is there a specific situation you have in mind?
The CommandManager.CanExecute method is a way to attach a CanExecute event handler to a UI element, so that when the CanExecute of the RoutedUICommand bubbles up the visual tree, it can trigger your CanExecute event handler. It is just a different way to attach a CanExecute event to an element for different scenarios, but the end result is the same as adding a CommandBinding to the CommandBindings collection of a UIElement.
Is there an event that gets fired when one clicks the ColumnHeader of a Datagrid to trigger a sort on that column ?
Thanks in advance
DataGridColumnHeader is a control itself so you should be able to assign an handler to its MouseLeftButtonDown event programatically.
I am using the method described here to attach a ViewModel ICommand to the LostFocus event of a Combobox, by setting CommandBehavior.RoutedEventName="LostFocus". I expected the event to fire at the same time the binding for UpdateSourceTrigger=LostFocus fired, but this turns out not to be the case.
The selecteditem Binding UpdateSourceTrigger=LostFocus fires whenever the keyboard tabs away, or after the user actually selects an item from the dropdown by clicking (not sure why this causes lostfocus, but at least it fires AFTER a selection is made).
The attached behavior event fires anytime the user clicks on the Combobox. Immediately. If using the keyboard it behaves normally, firing when you tab away from it. However, when using the mouse, the event fires when the control GAINS focus, before the user has even made a selection. Is there any way to make this behave like lostfocus does for the selecteditem?
Edit: I am curious if another answer exists, but I found a way around this problem, by setting up an additional binding. SelectedItem updates by defualt, handling the normal property change notifications, and selectedvalue updates on lostfocus, handling only the command I was trying to run. Binding looks like this:
SelectedItem="{Binding Path=SelectedCustomer, Mode=TwoWay}"
SelectedValuePath="CM_CUSTOMER_ID"
SelectedValue="{Binding Path=CustomerLostFocus, UpdateSourceTrigger=LostFocus}"
You would need to check the OriginalSource of the event arguments for the LostFocus event:
The LostFocus event is a bubbling event. This means that if multiple
LostFocus event handlers are registered for a sequence of objects
connected by parent-child relationships in the object tree, the event
is received by each object in that relationship. The bubbling metaphor
indicates that the event starts at the object that directly receives
the input condition, and works its way up the object tree. For a
bubbling event, the sender available to the event handler identifies
the object where the event is handled, not necessarily the object that
actually received the input condition that initiated the event. To get
the object that initiated the event, use the OriginalSource value of
the event's RoutedEventArgs event data.
So for the ComboBox, you may receive events for the various focusable elements inside the ComboBox.
In WPF, I have raised PreviewMouseLeftButtonDown for a TabItem. I want this event to raise when TabItem's header is clcked. The TabItem's content is a TextBox and a Button, but whenever I click on the TextBox or Button, TabItem's PreviewMouseLeftButtonDown is raised. How can it be avoided?
Please help,
Thanks
This is due to tunneling in Wpf, you can stop tunneling by handling this event at root and in the handler write:
e.Handled = true;
then it will not tunnel down.
And then if you want to handle it for your textbox or button
use AddHandler method to assign handler to the event instead of using normal += format.
button.AddHandler(Button.ClickEvent, new RoutedEventHandler(OnbuttonClick));
Check this for details:
http://msdn.microsoft.com/en-us/library/ms742806.aspx#event_handing