I have a search screen with some textboxes and a Search button as the default. If I type in a textbox and I CLICK the button, everything's great. But if I press enter within a text box, the button command fires but the binding on whatever text box I was in does NOT fire and so my criteria doesn't make it to the view model to get filtered on.
I know one fix is to set the bindings on the text boxes to PropertyChanged, but this seems like way overkill. I might have logic in the viewmodel doing stuff and I don't want that to trigger on every single keystroke.
What I really want is a way for the button itself to either trigger a focus change or somehow trigger binding. Or to have the textbox trigger binding if focus is lost OR I press enter OR a command is executed from anywhere
One way to do this is with a BindingGroup.
http://msdn.microsoft.com/en-us/library/system.windows.frameworkelement.bindinggroup.aspx
If your TextBox(es) and Button are both contained within a Grid (for example), you would add a BindingGroup like this:
<Grid>
<Grid.BindingGroup>
<BindingGroup Name="bindingGroup1"/>
</Grid.BindingGroup>
Then you could add a Click event handler to your button and call CommitEdit() on the BindingGroup (which the Button and TextBox inherit from the Grid):
private void button1_Click(object sender, RoutedEventArgs e)
{
(sender as FrameworkElement).BindingGroup.CommitEdit();
}
The Button.Click event fires before the CommandBinding, so any databound TextBox or any other databound controls within that BindingGroup should be updated before your view model command gets executed.
I've had the exact scenario you just mentioned. The trick I use is an attached behavior that sits on a control and listens for the PreviewKeyDown event. It checks if enter is being pressed. If so it forces the control to lose focus, thus causing the binding to fire before the command executes.
A simpler approach (rather than using a binding group) is to use the default button's click event to set the focus to itself. As this happens before the command is executed it means the ViewModel is updated in time.
private void button1_Click(object sender, RoutedEventArgs e)
{
(sender as Button).Focus()
}
And if you really hate code behind, you could always write an attached property...
I've bound an ObservableCollection to a DataGrid. When I change values in the DataGrid, the RowEditEnding event is raised. But the e.Row.Item is the object before editing, so you don't see the new values. I understand that because of the EditEnding. In Silverlight you have an EditEnded event, how can I get the object with the new values when I edit the DataGrid.
thanks,
Filip
From https://social.msdn.microsoft.com/Forums/en-US/c38fc695-d1ec-4252-87b7-feb484ee01e4/wpf-4-datagrid-roweditending, change the UpdateSourceTrigger of the Binding to PropertyChanged. The Property will then be updated immediately, before the RowEditEnding event, and the new value can be accessed from the RowEditEnding event handler.
For example, for a DataGridComboBoxColumn
SelectedItemBinding="{Binding ForTestResult, UpdateSourceTrigger=PropertyChanged}"
This seems a very simple way to solve this issue.
In addition, although I have not tried it, I think it should be easy to also access the original value before editing if your object implements IEditableObject.
Well, maybe this may help: http://wpf.codeplex.com/Thread/View.aspx?ThreadId=39356
http://blogs.msdn.com/b/vinsibal/archive/2009/04/14/5-more-random-gotchas-with-the-wpf-datagrid.aspx
Or this, see point number 5.
You'll have to tinker with it to get what you want I think, but I hope that helps! Or points you in a good direction.
This solution seems simple enough. Referred from msdn forum.
private void dgEmployees_RowEditEnding(object sender, DataGridRowEditEndingEventArgs e)
{
Action action = delegate
{
Employee emp = e.Row.Item as Employee;
//do something nice to the employee
};
Dispatcher.BeginInvoke(action, System.Windows.Threading.DispatcherPriority.Background);
}
Attach to the ObservableCollection's changed event.
I bound to a DataTable and used the RowChanged event.
My fresh and IMHO fastest way is to add bool rowEdited=false, then set it to true inside DataGrid_RowEditEnding and put your code for 'editEnded' inside DataGrid_LayoutUpdated:
if (rowEdited)
{
//main code here//
rowEdited=false;
}
.
Is there an event handler that will be called when an item is added in a listbox in WPF?
Thanks!
The problem is that the INotifyCollectionChanged interface which contains the event handler is explicitly implemented, which means you have to first cast the ItemCollection before the event handler can be used:
public MyWindow()
{
InitializeComponent();
((INotifyCollectionChanged)mListBox.Items).CollectionChanged +=
mListBox_CollectionChanged;
}
private void mListBox_CollectionChanged(object sender,
NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
// scroll the new item into view
mListBox.ScrollIntoView(e.NewItems[0]);
}
}
Ref.
Josh's advice about the observable collection should also be considered.
Take a different approach. Create an ObservableCollection (which does have such an event) and set the ItemsSource of the ListBox to this collection. In other words, in WPF you should think about the problem differently. The control isn't necessarily what is being modified ... the collection behind it is.
UPDATE
Based on your comment to Mitch's answer which indicates your binding source is actually an XML document, I suggest looking into hooking up to the XObject.Changed event of the XML document/element/etc. This will give you change information about the XML structure itself - not the ItemCollection which is an implementation detail you shouldn't need to consider. For example, ItemCollection (or any INotifyCollectionChanged) doesn't guarantee an individual event for every change. As you noted, sometimes you'll just get a generic reset notification.
I have a UserControl which contains a TextBox. When my main window loads I want to set the focus to this textbox so I added Focusable="True" GotFocus="UC_GotFocus" to the UserControls definition and FocusManager.FocusedElement="{Binding ElementName=login}" to my main windows definition. In the UC_GotFocus method i simply call .Focus() on the control i want to focus on but this doesn't work.
All i need to do is have a TextBox in a UserControl receive focus when the application starts.
Any help would be appreciated, thanks.
I recently fixed this problem for a login splash screen that is being displayed via a storyboard when the main window is first loaded.
I believe there were two keys to the fix. One was to make the containing element a focus scope. The other was to handle the Storyboard Completed event for the storyboard that was triggered by the window being loaded.
This storyboard makes the username and password canvas visible and then fades into being 100% opaque. The key is that the username control was not visible until the storyboard ran and therefore that control could not get keyboard focus until it was visible. What threw me off for awhile was that it had "focus" (i.e. focus was true, but as it turns out this was only logical focus) and I did not know that WPF had the concept of both logical and keyboard focus until reading Kent Boogaart's answer and looking at Microsoft's WPF link text
Once I did that the solution for my particular problem was straightforward:
1) Make the containing element a focus scope
<Canvas FocusManager.IsFocusScope="True" Visibility="Collapsed">
<TextBox x:Name="m_uxUsername" AcceptsTab="False" AcceptsReturn="False">
</TextBox>
</Canvas>
2) Attach a Completed Event Handler to the Storyboard
<Storyboard x:Key="Splash Screen" Completed="UserNamePassword_Storyboard_Completed">
...
</Storyboard>
and
3) Set my username TextBox to have the keyboard focus in the storyboard completed event handler.
void UserNamePassword_Storyboard_Completed(object sender, EventArgs e)
{
m_uxUsername.Focus();
}
Note that calling item.Focus() results in the call Keyboard.Focus(this), so you don't need to call this explicitly. See this question about the difference between Keyboard.Focus(item) and item.Focus.
Its stupid but it works:
Pop a thread that waits a while then comes back and sets the focus you want. It even works within the context of an element host.
private void ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
System.Threading.ThreadPool.QueueUserWorkItem(
(a) =>
{
System.Threading.Thread.Sleep(100);
someUiElementThatWantsFocus.Dispatcher.Invoke(
new Action(() =>
{
someUiElementThatWantsFocus.Focus();
}));
}
);
}
Just recently I had a list-box that housed some TextBlocks. I wanted to be able to double click on the text block and have it turn into a TextBox, then focus on it and select all the text so the user could just start typing the new name (Akin to Adobe Layers)
Anyway, I was doing this with an event and it just wasn't working. The magic bullet for me here was making sure that I set the event to handled. I figure it was setting focus, but as soon as the event went down the path it was switching the logical focus.
The moral of the story is, make sure you're marking the event as handled, that might be your issue.
“When setting initial focus at application startup, the element to
receive focus must be connected to a PresentationSource and the
element must have Focusable and IsVisible set to true. The recommended
place to set initial focus is in the Loaded event handler"
(MSDN)
Simply add a "Loaded" event handler in the constructor of your Window (or Control), and in that event handler call the Focus() method on the target control.
public MyWindow() {
InitializeComponent();
this.Loaded += new RoutedEventHandler(MyWindow_Loaded);
}
void MyWindow_Loaded(object sender, RoutedEventArgs e) {
textBox.Focus();
}
since i tried a fuzquat's solution and found it the most generic one, i thought i'd share a different version, since some complained about it looking messy. so here it is:
casted.Dispatcher.BeginInvoke(new Action<UIElement>(x =>
{
x.Focus();
}), DispatcherPriority.ApplicationIdle, casted);
no Thread.Sleep, no ThreadPool. Clean enough i hope.
UPDATE:
Since people seem to like pretty code:
public static class WpfExtensions
{
public static void BeginInvoke<T>(this T element, Action<T> action, DispatcherPriority priority = DispatcherPriority.ApplicationIdle) where T : UIElement
{
element.Dispatcher.BeginInvoke(priority, action);
}
}
now you can call it like this:
child.BeginInvoke(d => d.Focus());
WPF supports two different flavors of focus:
Keyboard focus
Logical focus
The FocusedElement property gets or sets logical focus within a focus scope. I suspect your TextBox does have logical focus, but its containing focus scope is not the active focus scope. Ergo, it does not have keyboard focus.
So the question is, do you have multiple focus scopes in your visual tree?
I found a good series of blog posts on WPF focus.
Part 1: It’s Basically Focus
Part 2: Changing WPF focus in code
Part 3: Shifting focus to the first available element in WPF
They are all good to read, but the 3rd part specifically deals with setting focus to a UI element in a UserControl.
Set your user control to Focusable="True" (XAML)
Handle the GotFocus event on your control and call yourTextBox.Focus()
Handle the Loaded event on your window and call yourControl.Focus()
I have a sample app running with this solution as I type. If this does not work for you, there must be something specific to your app or environment that causes the problem. In your original question, I think the binding is causing the problem.
I hope this helps.
After having a 'WPF Initial Focus Nightmare' and based on some answers on stack, the following proved for me to be the best solution.
First, add your App.xaml OnStartup() the followings:
EventManager.RegisterClassHandler(typeof(Window), Window.LoadedEvent,
new RoutedEventHandler(WindowLoaded));
Then add the 'WindowLoaded' event also in App.xaml :
void WindowLoaded(object sender, RoutedEventArgs e)
{
var window = e.Source as Window;
System.Threading.Thread.Sleep(100);
window.Dispatcher.Invoke(
new Action(() =>
{
window.MoveFocus(new TraversalRequest(FocusNavigationDirection.First));
}));
}
The threading issue must be use as WPF initial focus mostly fails due to some framework race conditions.
I found the following solution best as it is used globally for the whole app.
Hope it helps...
Oran
I converted fuzquat's answer to an extension method. I'm using this instead of Focus() where Focus() did not work.
using System;
using System.Threading;
using System.Windows;
namespace YourProject.Extensions
{
public static class UIElementExtension
{
public static void WaitAndFocus(this UIElement element, int ms = 100)
{
ThreadPool.QueueUserWorkItem(f =>
{
Thread.Sleep(ms);
element.Dispatcher.Invoke(new Action(() =>
{
element.Focus();
}));
});
}
}
}
I've noticed a focus issue specifically related to hosting WPF UserControls within ElementHosts which are contained within a Form that is set as an MDI child via the MdiParent property.
I'm not sure if this is the same issue others are experiencing but you dig into the details by following the link below.
Issue with setting focus within a WPF UserControl hosted within an ElementHost in a WindowsForms child MDI form
I don't like solutions with setting another tab scope for UserControl. In that case, you will have two different carets when navigating by keyboard: on the window and the another - inside user control. My solution is simply to redirect focus from user control to inner child control. Set user control focusable (because by default its false):
<UserControl ..... Focusable="True">
and override focus events handlers in code-behind:
protected override void OnGotFocus(RoutedEventArgs e)
{
base.OnGotFocus(e);
MyTextBox.Focus();
}
protected override void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
{
base.OnGotKeyboardFocus(e);
Keyboard.Focus(MyTextBox);
}
What did the trick for me was the FocusManager.FocusedElement attribute. I first tried to set it on the UserControl, but it didn't work.
So I tried putting it on the UserControl's first child instead:
<UserControl x:Class="WpfApplication3.UserControl1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Grid FocusManager.FocusedElement="{Binding ElementName=MyTextBox, Mode=OneWay}">
<TextBox x:Name="MyTextBox"/>
</Grid>
... and it worked! :)
I have user control - stack panel with two text boxes.The text boxes were added in contructor, not in the xaml. When i try to focus first text box, nothing happend.
The siggestion with Loaded event fix my problem. Just called control.Focus() in Loaded event and everthing.
Assuming you want to set focus for Username textbox, thus user can type in directly every time it shows up.
In Constructor of your control:
this.Loaded += (sender, e) => Keyboard.Focus(txtUsername);
After trying combinations of the suggestions above, I was able to reliably assign focus to a desired text box on a child UserControl with the following. Basically, give focus to the child control and have the child UserControl give focus to its TextBox. The TextBox's focus statement returned true by itself, however did not yield the desired result until the UserControl was given focus as well. I should also note that the UserControl was unable to request focus for itself and had to be given by the Window.
For brevity I left out registering the Loaded events on the Window and UserControl.
Window
private void OnWindowLoaded(object sender, RoutedEventArgs e)
{
ControlXYZ.Focus();
}
UserControl
private void OnControlLoaded(object sender, RoutedEventArgs e)
{
TextBoxXYZ.Focus();
}
I set it in the PageLoaded() or control loaded, but then I'm calling WCF async service and doing stuff that seems to lose the focus. I have to to set it at the end of all the stuff I do. That's fine and all, but sometimes I make changes to the code and then I forget that I'm also setting the cursor.
I had same problem with setting keyboard focus to canvas in WPF user control.
My solution
In XAML set element to Focusable="True"
In element_mousemove event create simple check:
if(!element.IsKeyBoardFocused)
element.Focus();
In my case it works fine.
Which event fires when DataGrid's source is updating? I've tried DataContextChanged and SourceUpdated but it never worked out.
Actually I need a simple thing. I want, if there is a new row comes, scroll the GridView's scrollbar down to the bottom to see what it was.
I had the same problem and I manage it this way
DataGrid myGrid = new DataGrid();
CollectionView myCollectionView = (CollectionView)CollectionViewSource.GetDefaultView(myGrid.Items);
((INotifyCollectionChanged)myCollectionView).CollectionChanged += new NotifyCollectionChangedEventHandler(DataGrid_CollectionChanged);
You then need to implement the logic in the event handler DataGrid_CollectionChanged.
Set NotifyOnTargetUpdated = true for the ItemsSource binding and handle TargetUpdated event. If you've multiple bindings, then look for DataTransferEventArgs Property to find out if the target is ItemsSource or not.
If you are trying to have the grid refresh when something is added to the database itself, that's not going to happen. I'm more familiar with WinForms than WPF but I'm assuming there is no magical way to keep a grid in sync with the database without writing some background process that continuously checks for database changes.
If you are updating the actual data source of the grid (ex. Collection) then that will update the grid.
For my part i've used SelectionChange notification which raise each event Del/Add/Edit/Select
It's work very well
private void dataGrid_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
Console.WriteLine("hi");
}