Is there an ItemActivated event (like in Windows Forms) in the WPF ListBox or ComboBox controls? I can't see one.
It seems crazy for there not to be some event doing the same kind of thing - so does it just go by another name? If not, is there another easy way to do it? I've seen various blog posts about this but they all seem to involve subclassing the control and other things like that. I'm sure the WPF designers realised this was pretty much the most common thing that is done with a ListBox or ComboBox!
I'm basically looking for an event which will fire when the item is activated, telling me which item has activated and allowing me to access the properties of that item.
from what I understand of your description, you want to look at the SelectedItem (individual) and SelectedItems (a collection) properties. Additionally, there should be a SelectionChanged event (though I'm not certain about that naming there).
Related
Assume we have a Combobox in a winforms application which its items bound to a Bindingsource.
I need to fire an event when the user changes the selected item in the combobox.
Should I handle the combobox.selectedindexchanged event or bindingsource.currentchanged event. Which is better in case of performance or anything else?
I've searched a lot to find an article or something about it, but can't find something straight and clear. I appreciate any suggestion or workaround.
UPDATE
I need to call a function base on the selected object ID after user select an Item from combobox. (ID is accessible from both Combobox1.SelectedValue and bindingSource1.Current.ID). In this case which event shouldI choose?
If you wish to handle event when end user selects any item in UI then you should go with combobox.selectedindexchanged because bindingsource.currentchanged can be triggered for number reasons such as mentioned here on MSDN blog, BindingSource.CurrentChanged Event so in case, you need to handle an event for any of the reason mentioned in MSDN then it will unnecessarily go through logic you might have coded for selection change event. Your code should be specific, while handling events.
If a ComboBox is bound to a BindingSource you usually leave it at that. If you do need to tap into events you're better off creating more properties in the Business Object. For example say you want to disable a button if the combobox is Index Value == 0, simply create a property in the Business Object that the Enabled property of the Button is bound to, eg:
public virtual bool IsFunctionEnabled
{
get { return (An_Items_SelectedIndex > 0); }
}
If you really need to do stuff in the ComboBox's selected index change event I would lean towards doing it in the Presentation Tier as I don't recommend mucking with binding source controls or their events.
The best solution is handling everything in your Business Objects and binding your controls via BindingSources. Doing any logic in the Presentation Tier makes it hard to test and changing anything in the BindingSources add a lot of testing.
After all, I am getting to know it should be better to use Combobox.SelectedIndexChanded event, because I am interacting with a user and looking for a response from UI. Although here the events do the same for me, but Bindingsource.CurrentChanged event can be used in case I wanted to track the current object changes from anywhere like a list change or something, not exactly the UI. Its better to use combobox events here I believe.
i am creating my first mvvm app in wpf, i came to a point where i need to drag and drop files into a ListBox, i couldn't see any other way to do it but use the DragEnter and the Drop events, then add the dropped files to my collection by casting the DataContext of the view to my ViewModel and the accessing the collection from there, and that is working really great.
something like this in my View in the drop event
(this.DataContext as ImageViewModel).ToUpload.Add(new ImageModel() { localfilelocation = fi.FullName })
but is there anyother way do it?
To be honest, dragging and dropping is probably one of those activities that MVVM finds most difficult to fit naturally into it's paradigm. However, the most common way of doing this is by using Attached Behaviours. A DragDropBehaviour, sub-classing Behavior<T> will allow you to hook into those events on the ListBox and have the advantage of being totally re-usable.
A good example of this can be found here.
Ok. This seems like an incredibly basic use case but fore some reason I am having an issue finding a common solution across control types.
Heres the use case:
A form is presented to the user with any editable controls. (Text box, combo, grid etc.).
The user edits a value in the control and tabs out.
Expectation is that I can wire to an event like Lost Focus and do "foo" with the changed value.
The user then gives focus back to the control and tabs out without making an edit.
Expectation is that whatever event I am wired to I can check if the value has been changed.
Is there one common event across controls that will only fire when the user has finished editing( such as tab out or enter ) and allow me to check previous state vs. current state?
Jason, you may want to look into Binding and DependencyProperties in WPF instead of tracking events in your form. You would bind a class to your form which exposes properties to be changed. Using DependancyProperties a single event is fired called "PropertyChanged".
Unfortunately is is a broad topic, but you will really get the full benefit of the WPF programming model. Searches on "dependency properties in wpf" will give you some good examples.
I think maybe this is Focus issue. There exist two different focus types: keyboard focus and logical focus. The the control that has keyboard focus is the one that has the caret, in what the user press a key and the control process that input. The a control may have the logical focus but not having the keyboard focus. Please check this in the MSDN article "Input Overview". About the other question, maybe you could process the TabControl.SelectedItemChanged for taking the event when a tab item selection changed.
Hope this is helpful to you...
What you may be interested in is implementing INotifyPropertyChanging (not just INotifyPropertyChanged).
As noted in the answer of this question, the INotifyPropertyChangING does not prevent you from changing a value, but to detect WHEN something DOES change, and what it's new value is going to be.
Hope it helps in your solution needs.
As the previous answers suggested, you would be better off by implementing a view - viewmodel structure, with your viewmodel having implemented INotifyPropertyChanged, and thus allowing you to bind to properties that will announce their changes to the UI.
If you don't want to do this, you can eventually subscribe on your input elements to the PreviewKeyUp event, check if the Tab key has been pressed and proceed from there.
I want to make a complex layout, and would like advice on the best way to go about this.
Here is the behaviour I'm looking for: Layout of some text blocks and some images, such that a tap anywhere on the layout will go to another related page to that item. I want a long list of this item in a scroll viewer.
First, I tried to make a grid, add the items in it, then add this grid in the outer grid, the main one for pressing, I made an event handler for mouse click, but a problem appeared; that when I try to scroll "on the item to view the all list" the event handler fired!, I tried the mouseButton up and down, and the same happen
Second, I'm not sure if it's an efficient way to make it.
I want a good way to design this complex layout, and of course it will be a programmatic way, and a way to recognize the item I press on.
It sounds like you're trying to create your own ListBox control. Using this will give you the scrolling functionality for free, and you can use the ListBox's SelectionChanged event to determine when an item has been clicked.
The best way to design the layout will depend on how complex it actually is. If it merely contains an image and some text, you should have no problem hand-coding that in XAML. If there's a lot more to it than that, I'd recommend looking into Microsoft's Blend tool. Whichever route you choose to produce the XAML, you will place the code in the ListBox's ItemTemplate, which determines how each item in the ListBox is displayed.
A good walkthrough of something similar to what you're doing can be found at http://weblogs.asp.net/psheriff/archive/2010/10/27/windows-phone-list-box-with-images.aspx
I'm having issues using a GridView as a ListView's View, what I want to do is fire an event when a user makes a selection from a combobox within the Gridview and pass the selected item within the event.
My first issue is that when the user clicks the combobox within a row, the row isnt selected (meaning the selecteditem stays null unless they click elsewhere first). Is there a clean way to do this without trying to catch mouse clicks or anything?
Secondly theres no selectionchangecommited event on a WPF combobox, is there a cleaner way to check if a user has manually selected an option other than checking if the combobox is enabled?
Thanks
I am seeing a similar behavior. My hypothesis is that one or more layers of the DataTemplate of each item in the list is swallowing the RoutedEvent that should have resulted in a new selection. Is it possible to, in a generic way, tell the items in the DataTemplate that they should never stop the event from bubbeling or tunneling further, without having to override every focus-triggering event handler in code behind?
I 'solved' my issue by using the WPF Toolkit grid (http://wpf.codeplex.com/Release/ProjectReleases.aspx?ReleaseId=29117) and a series of selected items, which is probably a cleaner solution anyway.
Doesn't explain the behavior of the GridView, which is to me unusual
Original link has died, believe this to be the one https://github.com/xceedsoftware/wpftoolkit/wiki/DataGrid