My application has two tabs in a TabControl.
I have (model) class (implementing INotifyPropertyChanged) bound to a the controls in the first tab via DataConext. Data binding works fine. I then replace the instance assigned to the DataContext with a new instance. Then the new values are not shown. As soon as I switch to the second tab and back the values are visible. It appears as if the data binding need some kind of kick ass to start working.
How could I force the view to re-bind programmatically?
Related
I have an ItemsControl binding to a collection in the ViewModel. As a result of user input, a new item gets added to the collection and this gets displayed on the View.
The item is also a View-ViewModel pair, the View contains a TextBox that I would like to receive focus immediately after being added to the collection.
How do I set the focus to a TextBox without referencing the View from within the ViewModel? Are attached properties the way to go here?
well you can do this by creating a behaviour..
have a look here to get an idea of behaviours controlling focus
I have a WPF TabControl with two TabItems. In both tabItems I have a textbox with the Text property bound to a property in my ViewModel. The problem is that the binding in the second tab (the one "hidden" by the first tab) is not working. I have two cases:
I run the app, I run the command that would fill the text in the second tab, I select the tab: in this case the binding works: I can see the textbox filled with data. But if I run again the command the textbox does not get updated anymore. It looks like the binding works, but only once.
The second case is if I run the app, and then, before running the command, I select the second tab. In this case the binding does not work at all.
If I move the second tab to the first position, then the binding will work for this tab. (but it will stop working for the other one)
Does someone knows about a worksround for that
Your ViewModel has to implement INotifyPropertyChanged interface.
Also you have to set the UpdateSourceTrigger property of your binding to "PropertyChanged". After this changes your app should working as expected.
I can do element-to-element binding in WPF: For example, I've got a window that has a slider control and a textbox, and the textbox dynamically displays the Value property of the slider as the user moves the slider.
But how do i do this across separate windows (in the same project, same namespace)?
The reason is that my main application window containing the textbox has a menu option that will open an 'options' window containing the slider control.
You should use a (global) ViewModel, containing the data you need to share, and bind to the property from that ViewModel.
This way the changes in either of windows are reflected in the bound data object, and back.
You dont. Point. Databinding has to go to an element accessible in the same control.
What you can do is have the options menu bind go an object that it has in it's own code (property) that gets populated to the same object the othe rwindow uses as data source.
I have WPF window that uses a dockpanel and the menu control. I have the code to create the menu options based on a user ID.
Within this window, I have a frame that contains a WPF page. I carry out all the authentication on the page and then have a user ID for the window to use. However, I cannot get the parent window to "refresh" and create the menu bar with the new ID information. When the window loads, I do not run through the commands to display the menu bar. I have tried putting that in its own, public, function and calling it from the page but that does not seem to work.
There must be a window method that I'm missing that can make the menu bar display based on the call from the page.
It sounds like you're still thinking in procedurally, in WinForms style. What you describe would be necessary in WinForms, but in WPF it is usually much easier: just use data binding. As long as your menu items are generated from a "UserID" dependency property (or enabled/disabled based on it), then all you need to do is set the UserID DependencyProperty and the UI will update itself with no additional code.
Here is how to get the UserID into a DependencyProperty of the Window or a context object:
In your Window or a context object create a "UserID" DP
Make your Window or your a context object the DataContext of the page
At the end of the authentication code, set DataContext.UserID (or alternatively create a UserID property on the page, and have the Window bind to it with a two way binding)
Once you have the UserID in a DependencyProperty, there are many ways to update the menu items automatically whenever it changes:
In each menu item, bind its visibility to the UserID DP on the window using an appropriate converter (using the converter parameter to distinguish between items), -OR-
Use a converter for setting ItemsSource so you filter your items, -OR-
Create a PropertyChangedCallback that sets a filter on the CollectionView you use for menu items, -OR-
Some other technique (there are many other good ways to do this)
For typical situations we're talking about less than 10 lines of C# here, not counting the DependencyProperty declarations.
I have a WPF ListView that is bound to a BindingList<T>. The binding works like a charm, but I have to tab out of the cell to get the bound property to update....this is an issue because most users don't tab out of the last column before clicking the save button.
How do I force the list view to "persist" the changes to the bound DataContext without doing something hackish.
Bindings in WPF have a property called "UpdateSourceTrigger" which tells the Binding when to update the thing the UI is bound to. By default, it's set to "LostFocus" for the Text property which is what you're most likely using.
Change the trigger to "PropertyChanged" in your binding like this:
Text="{Binding Foo,UpdateSourceTrigger=PropertyChanged}"
... and now the source "Foo" property will be updated as the Text changes in the UI.
There's also an "Explicit" setting for UpdateSourceTrigger which is handy if you need to hold off writing any changes to the source until, say, the user clicks the OK button.