I am deriving from combobox (WinForms) and am providing a new implementation for the Selectedvalue property.
It works fine as is, but any change to the selectedvalue property is not updating other controls bound to the same "binding context" to change their values accordingly.
I did try adding the BindableAttribute(true) to the property, but still it does nottrigger the change in value to the other linked controls.
The control's DataBindings.add(...) is all set up. And other controls are also bound to the same data filed on the same datasource.
Any ideas what i am doing wrong.
Have you called your base class' implementation of overridden methods? It's possible that failing to call the base class implementation is accidentally circumventing the code that fires various event plumbing.
Related
I have a combobox, and in the design view I have it databound to a bindingsource as follows:
this.itemTypeComboBox.DataBindings.Add(new System.Windows.Forms.Binding("SelectedValue", this.itemTypeContainerBindingSource, "ItemType", true));
this.itemTypeComboBox.DataBindings.Add(new System.Windows.Forms.Binding("Text", this.itemTypeContainerBindingSource, "ItemType", true));
In the code behind in the load event I have the following:
// bind the combobox to the enum
this.itemTypeComboBox.DataSource = Enum.GetValues(typeof(OpticalItemType));
// bind a custom object to the datasource
this.itemTypeContainerBindingSource.DataSource = customObjectContainer;
The "customObjectContainer" is a single object that contains a property "ItemType" that is bound to the combobox, and all properties of the object use change notification through "INotifyPropertyChanged".
In my code behind, if I programmatically change the custom object, the changes are reflected in the combobox. However, if I change the combobox through the UI, the bindingsource, and hence the custom object do not reflect the changes.
Any ideas what I am doing wrong?
As it is a singular object, it cannot be to do with using BindingList etc.
UPDATE 1:
Ok, whenever I change the combobox through the UI, it never changes the underlying object, the setter is never hit for the property in the custom object. However, I have just noticed that if I tab off of the control, it then fires the setter, and changes the underlying object. Why would this be?
PROBLEM SOLVED:
It appears, the issue was with my binding. I added "DataSourceUpdateMode.OnPropertyChanged" to the bindings, and it works now!!
The issue was with my binding. I added "DataSourceUpdateMode.OnPropertyChanged" to the bindings, and it works now!!
I have a View with a dataGrid. This datagrid bind a property in the ViewModel that is an ObservableCollection.
I edit some data in the dataGrid, and a field is updated by code, because it depends on some operations. Well, if I check the item in the observable collection, I can see that all the data is correct, but the info in the dataGrid is no refresh.
I want to force the refresh because I know that the observableCollection only raise the change property event when I add o remove items, but not if I edit one of them.
Because I am use Entity Framework 4.1, really the ItemsSource of the dataGrid is the local of the DbSet, so I don't know how to implement the notifyPorpertyChanged in the classes of the model edmx, and I am looking for an alternative, like to force refresh the dataGrid.
Because the property of the ViewModel that I use to bing the ItemsSource of the dataGrid is a reference to the local, I mean that to set the property I do myProperty = myContext.MyTable.Local and that raise the event PropertyChanged that I implement in my ViewModel, I try to do myProperty = myContext.MyTable.Local again to try to raise the event and force the refresh of the dataGrid, but it does not work.
What alternatives do I have?
Make sure that you have the Binding Mode set to TwoWay. Implement in the set portion of your property OnPropertyChanged and the rest should take care of itself.
I have a ListBox bound to an ObservableCollection of type T - each ListBoxItem is a checkbox with IsChecked bound to a bool property in T. I want to validate the checked items in the ListBox so that at least one checkbox must be ticked - if none of the check boxes are ticked I want to show a red border (standard validation notification) around the ListBox.
How do I go about doing that? Can I use ValidatesOnDataErrors?
Implement IDataErrorInfo in the class that exposes the ObservableCollection<T> property and make the indexer return an error for that property's name if all of the objects in the collection have a value of false in their boolean property. Then use the DataErrorValidationRule in your binding's ValidationRules.
Your goal is to validate selected items of a ListBox: at least one selected item is required. First, there are different ways to handle the selection itself:
a) You can use the ListBox selection mechanism via ListBox.SelectedItem.
I guess, you can specifiy the binding as SelectedItem="{Binding SelectedThing, ValidatesOnNotifyDataErrors=True}" and WPF's regular validation works. Not sure, if this works well with multi-selection.
b) You can use ListBox.SelectedItems. Binding is not possible and needs to be faked via code behind event handler. Thus, WPF's validation cannot trigger here.
c) You use your own IsSelected property (or similar) per item, either explicitely bound to your viewmodel via CheckBox or implicitely via ListBoxItem.IsSelected (via ListBox.ItemContainerStyle).
From here you could create a bool IsValidSelection property in your viewmodel that updates whenever the selection changed. Or you can run validation rules on any of the resulting properties of your viewmodel (e.g. SelectedItems). However, you don't validate the bound ListBox.ItemSource itself! Therefore WPF's standard mechanisms don't work (the list box doesn't get a red border or whatever).
Workarounds
You can explicitely create error notifications by showing an otherwise invisible Label and binding its visibility to the above-mentioned bool IsValidSelection property. This is a very explicit way, not using WPF validation at all.
You can modify your INotifyDataErrorInfo (or similar) implementation to trigger errors on a different property name. This is not possible, if you use a generic ValidatableViewModel<T> (like me). I guess this was the intention of the other answer.
I have a business object that comes from the core of the application. That object does not inherit from INotifyPropertyChanged. It contains some property that my XAML code bind to it.
I only want to update the properties not the UI dynamically (OneWayToSource style).
By example, if I change the text of a text box, the source item does not get updated.
It is a limitation of silverlight that if the object does not implement INotifyPropertyChanged or use DepencyProperties that the source of the binding cannot be updated?
The source property does not need to be a dependency property nor does the class that exposes it need to implement INotifyPropertyChanged.
If you have the binding on the TextBox set to use the TwoWay mode editing the text box should update the bound property even if it is a plain "vanila" property. Note by default the focus has to leave the TextBox in order for the binding to update.
If your business object has a set method on the property you want to update, then the value should be updated, provided the value you enter doesn't trigger an exception.
Not implementing INotifyPropertyChanged hinders just visual feedback.
Kind of an odd question- if I'm thinking of this the wrong way please let me know. I am using an infragistics dock manager, which manages tabs as well. So I can create a TabGroupPane, and then add multiple ContentPanes, each of which has its own tab.
In each content pane, I set my viewmodel:
<ContentPane>
<viewmodels:MyViewModelForTab1 />
</ContentPane>
So here's the problem- while using a mediator pattern for communication, my viewmodels have no idea if they are on the visible tab or not, so they are always working even if hidden. The TabGroupPane does have a SelectedTab property, as well as each ContentPane having an IsActive property.
So the question is how do I set that information in my ViewModel? Making my VM a dependency object seems like a bad idea since I already implement INotifyPropertyChanged. Using a CLR prop in my VM also doesnt work, since you cannot bind to it.
How can I get my VM to know if it is the datacontext of an active tab?
Thanks!
I would put an IsSelected property on my ViewModel and bind it to the TabItem's IsSelected dependency property.
This should allow you to hook into when it is updated and perform whatever you need. You don't need a mediator pattern here since you are communicatining from the View to the ViewModel.
Make sure your ViewModel is bound to the DataContext property of the view (specifically, that the Tab's DataContext is the ViewModel). The way you have it now, your ViewModel is the content of the element, not bound to the DataContext, as it should be:
<Tab.Resources>
<viewmodels:MyViewModelForTab1 x:Key="Tab1ViewModel" />
</Tab.Resources>
<ContentPane DataContext="{StaticResource Tab1ViewModel}" />
Or something like that...
I don't know the Infragistics model, so my apologies if this is inapposite, but here's how I implement this with regular items controls - tab control, list box, whatever.
Create a container view model class that includes an observable collection of items and exposes a SelectedItem property. Make the container class the data context of the items control. Bind the items control's SelectedItem property to the container class's.
Hook the item objects up to the PropertyChanged event of the container. So now when the selected item in the UI changes, the container view model notifies all of the items that SelectedItem has changed. Each item object's event handler can determine for itself whether or not it's now the selected item.
The item objects thus don't know any implementation details of the UI - you can unit test your classes outside of a UI and the logic will still work correctly.