when i bind one combobox with other combobox items... with the following code
<ComboBox ItemsSource="{Binding ElementName=cbo1, Path=Items}" Name="cbo2" />
it works fine but when i select something from cbo1 and come back to select something in cbo2.. it doesn't list anything nor cbo1 does...
what could be wrong?
The Items property is a CollectionView which wraps the ItemsSource, and includes things like the currently selected item, sort order, etc. If you set ItemsSource on an ItemsControl, your data is automatically wrapped in a CollectionView, and that's what gets set as the Items property. I suspect that this class isn't suitable for sharing between two controls.
If you're using ItemsSource to set the data on cbo1, you could maybe bind to ItemsSource instead? That is:
<ComboBox ItemsSource="{Binding ElementName=cbo1, Path=ItemsSource}" Name="cbo2" />
Haven't had chance to test this, but it's an educated guess :-)
Related
WPF, MVVM
I'm finding that if I use a CollectionViewSource with my ComboBox, when I close the window, an extra call to the SelectedValue Setter is executing, if SelectedValue is bound to a string property. If I set the ItemsSource binding directly to the VM, this call does not happen. The extra call is causing values to change in the VM, resulting in incorrect data. I have other ComboBoxes setup the same way, but they bind to integer values.
CollectionViewSource definition:
<CollectionViewSource x:Key="AllClientsSource" Source="{Binding AllClients}" >
<CollectionViewSource.SortDescriptions>
<scm:SortDescription PropertyName="ClientName" />
</CollectionViewSource.SortDescriptions>
</CollectionViewSource>
ComboBox with CollectionViewSource:
<ComboBox Grid.Column="2"
ItemsSource="{Binding Source={StaticResource AllClientsSource}}"
DisplayMemberPath="ClientName" SelectedValuePath="ClientId"
SelectedValue="{Binding Path=ClientId}"
Visibility="{Binding Path=IsEditingPlan, Converter={StaticResource BoolVisibility}}" />
ComboBox direct to VM (Forgoing sorting):
<ComboBox Grid.Column="2" ItemsSource="{Binding AllClients}"
DisplayMemberPath="ClientName" SelectedValuePath="ClientId"
SelectedValue="{Binding Path=ClientId}"
Visibility="{Binding Path=IsEditingPlan, Converter={StaticResource BoolVisibility}}" />
Can anyone tell me why there is an extra setter call using the CollectionViewSource? What's different about the string binding? Is there a way to properly work around it?
EDIT: I tried changing it up and using the SelectItem property on the ComboBox. Same result. So it seems that if the item is a scalar data type, it works as expected. If it's an object, you get an extra setter call with a null value. Again, if I remove the CollectionViewSource from the equation, it works as expected.
EDIT, AGAIN: I added a link to a sample project that illustrates the issue. Targets .Net 4.5.
Run the project.
Click to display View One
Select a Client and the client's name will display on the right.
Click to display View Two
Go back to View One - Note that the selected client is no longer selected.
Click to display View Three
Select a Region and the region's name is displayed on the right.
Go back to View Two
Go back to View Three - Note that the selected region is still selected.
The only difference between the views is that One and Two use a CollectionViewSource. Three binds directly to the ViewModel. When you move to a new tab from One or Two, the setter for the selected item is getting called with a null value. Why? What's the best work-around?
Thanks.
Apparently this is caused when the CollectionViewSource is removed from the visual tree... I moved the CollectionViewSource to the ViewModel and exposed it as a property and the issue is effectively worked-around.
I have a ListBox which displays more or less data depending on the level of details that users choose. The ListBox has a dynamic ItemsSource set in XAML:
ItemsSource="{Binding Items}"
and its default ItemTemplate is set using
ItemTemplate="{StaticResource FewDetails}"
in code behind I use
MyListBox.ItemTemplate = this.Resources["LotsOfDetails"] as DataTemplate
but the list box doesn't refresh.
The only way I've found to make this work is to use a CollectionViewSource as my ItemsSource, and to manually refresh the view using View.Refresh().
Any ideas why the straightforward solution doesn't work?
The subject line says it all really! I have a user control which can be bound successfully to, say, a Fullname object - i.e. it works ok.
I now need to show a list of these and, again, this works ok when the control is in a DataTemplate within ItemsControl.Template.
But, the control has a property (InEditMode) that is not a property of the Fullname object but of the object that has the FullnameList property to which the ItemsControl is bound, via ItemsSource. This InEditMode property works fine when the control is not in a list and is bound to parent sibling properties named, say, ParentInEditMode and ParentFullname.
The question is - what style of binding expression is required to 'get at' the edit mode property of the parent object when the control is an ItemsControl?
Or, should I re-design the Fullname object to contain an EditMode property?
Many thanks in advance!
Update:
The item (i.e. that which is in collection bound to the ItemsControl) does NOT have such a property. Code is very simple:
<ItemsControl ItemsSource="{Binding Path=FullnameList}">
...then...
<ItemsControl.ItemTemplate>
<DataTemplate>
<jasControls:NameView
NameValue="{Binding Path=.}"
InEditMode= ??????? />
The overall parent (the viewmodel for the window) has properties:
FullnameList
ParentInEditMode
Fullname (single item for testing NameView which works perfectly with this xaml outside of any list control using:
<jasControls:NameView NameValue="{Binding Path=Fullname}" InEditMode="{Binding Path=ParentInEditMode}"/>
I would like to apply the edit mode to the entire collection - making that flag part of Fullname does not seem right!?
I have found an answer to my own question, which I hope will help others.
The working syntax I have is this:
<StackPanel>
<ItemsControl ItemsSource="{Binding Path=FullnameList}">
...then...
<ItemsControl.ItemTemplate>
<DataTemplate>
<jasControls:NameView
NameValue="{Binding Path=.}"
InEditMode= "{Binding DataContext.ParentInEditMode,RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type StackPanel}}}" />
This correctly picks up the property that is a sibling of FullnameList and passes it to the data template item. More by luck than judgement, but I hope this is a valid way to do this!
For each Item in ItemsSource, ItemsControl creates the specified DataTemplate and to its DataContext it assigns the respective Item. Now every DataTemplate can bind to its item in its data context.
So I suppose your item does have a property "ParentInEditMode"; there should be no issue with binding to that property.
If it doesn't work, please update your question with some code.
I will try and explain this as concise as possible. I have 2 objects, the first which we will call object A that has an Id property and the second we will call object B, which has a ParentId property. The obvious relationship is that object B's ParentId is set to an object A's Id property. I am using the MVVM pattern, so on the viewmodel I have 2 ObservableCollections, one containing objects A the other objects B. On construction of the viewmodel, I create and fill the ObservableCollection<'A'> named ListItems. My xaml is simple,
<StackPanel>
<ListBox IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding ListItems}">
</ListBox>
<ComboBox SelectedValuePath="ParentId" SelectedValue="{Binding Path=ListItems/Id, Mode=OneWay}" ItemsSource="{Binding ComboItems}">
</ComboBox>
<Button Click="Button_Click" Content="Push Me"/>
</StackPanel>
As you can see the combobox's SelectedValue is bound to the ListItems current item's Id property. So essentially the listbox and combobox are in a master details.
If you press the button, it will fill the ObservableCollection<'B'> name ComboItems, which in turn populates the combobox. Now here is where the oddity begins. When I start the program, if the only thing I do is press the button, and then afterwords select an item in the listbox, the combobox will properly select an item due to the SelectedValue binding. But if I start the program and first select an item in the listbox and then press the button, the current combobox item will not change with the current listbox item. The binding appears to be forever broken. Does anyone know why this happens?
Ps. If I set the ItemsSource on the combobox before I set the SelectedValue/SelectedValuePath, the master/detail binding will never work. I know there is order to xaml, but that seems a little fragile. So if anyone has input on that also, I am all ears.
Thanks, Nate
EDIT -
When binding SelectedValue, it is very fragile. If the binding is working, i.e. have not selected anything in the listbox and then filled the combobox, if you choose an item in the combobox, the binding will break. After much time wasted with this, I chose to bind SelectedItem. This binding does not break in any of the conditions I have previously specified. I would however take any answers as to why SelectedValue binding is so ridiculous. Thanks again to all that have answered or will answer.
Yeah this is a problem we stumble upon quite a lot.
The problem is that after the ItemsSource property gets a new value, the SelectedValue binding will be cleared. Sucks, and until today we have not found a proper solution.
Here are a few workarounds:
Reset the SelectedValue binding in code, as soon as the new ItemsSource has been set. You can do this in a converter, or somewhere you'll know which will replace the ItemsSource binding (like the DataContextChanged event).
Instead of using the Binding on ItemsSource, try using a CollectionViewSource and a Filter. Put all your items in the CollectionViewSource object and filter the items when your combobox changes value.
Manually get your item the old fashion way when your listbox throws a SelectionChanged event.
Mind you, all solutions are not the prettiest in the book. I would go for option 2, its the cleanest IMO ;)
Hope this helps!
Tell me it ain't so.
I have a typical windows/file explorer like setup.
Left Side I have a TreeView all data bound showing nodes in a hierachy
Right Side I have a ListView showing Node.Properties
ListView has a IsSynchronizedWithCurrentItem property, which rocks. e.g. If I had another ListView showing a list of nodes and both listViews have this property set to true. Changing selection of node in NodesListView will update the PropertiesListView automatically.
Now I need the same thing with a NodesTreeView and a PropertiesListView... and seems like TreeView has no such property.
Is there a more 'the WPF way' kind of solution to this problem ? Or do I have to handle the NodeSelectionChanged event of the Tree and refresh the listView via code.
A really simple solution is to bind your "details" UI elements to the SelectedValue property of the TreeView. For example, if your TreeView looked like this:
<TreeView Name="CategoryName" ItemsSource="{Binding Source={StaticResource A_Collection}, Path=RootItems}" />
Then you could bind details UI elements (like a textbox) using:
<TextBox Text="{Binding ElementName=CategoryTreeView, Path=SelectedValue.Name}"/>
Would cause the text box to be bound to Name property of the items currently selected in the TreeView.
If you want to bind many UI items as details for the selected TreeView item, consider setting up a DataContext on the elemtent that contains all the details controls (DockPanel / Grid / StackPanel, etc).
<ListView Name="listView1"
ItemsSource="{Binding Path=SelectedItem.Modules,
ElementName=treeView1, Mode=OneWay}"
IsSynchronizedWithCurrentItem="True">
Where ".Modules" is the collection of child items off the selected treeview item you want to display. Don't worry about wiring up the "SelectedItemChanged" event on the treeview.
Why exactly it doesn't implement the property, I do not know, but i have a suggestion down below.
Your code above will work, however, it is not what the IsSynchronizedWithCurrentItem property does. Any ItemsControl binds to the ICollectionView of the ItemsSource property. To get that ICollectionView, we can call CollectionViewSource.GetDefaultCollectionView(object o). Depending on the type of object o, you get a different concrete implementation of the ICollectionView inteface. CollectionView and ListCollectionView are two concrete classes that come to mind.
The ICollectionView interface contains a member called CurrentItem. What the IsSynchronizedWithCurrentItem does is: whenever an item is clicked on the ItemsControl, it sets the CurrentItem for the collection view. The ICollectionView also has two events: CurrentItemChanging and CurrentItemChanged. When the IsSynchronizedWithCurrentItem property is set, the ItemsControl will update the SelectedItem based on what the ICollectionView's CurrentItem is. Makes sense?
In master/detail WPF scenarios, we simply are binding to ICollectionViews and their CurrentItem (the CurrentItem syntax is something like {Binding Items/Name}, where Name is the Name property on the collection's CurrentItem.
So although your code works for your purposes, it doesn't do what that property does. To do what the property does, you need to do the following:
When an item is selected, you need to figure out which collection it belongs to. How do we do this? I believe this is why TreeView doesn't implement it. The selected item is displayed in a TreeViewItem. The DataContext is the object itself, but what is the parent collection ? I guess to get it you could either cache it in some hashmap (silly, but will work) or you can walk up the logical tree and get the TreeViewItem's parent that happens to be an ItemsControl. The ItemsSource property will be your collection.
Get the ICollectionView for that collection.
Need to cast that ICollectionView into a CollectionView (ICollectionView doesn't implement CurrentItem setter)
Call SetCurrent(.. , ..) on the CollectionView instance
Now, anything that is bound to that ICollectionView's CurrentItem will be updated.
This became longer than I expected. Let me know if any further clarification is necesary.
My solution to this turned out to be pretty tiny.. don't know if it is equivalent to IsSynchronizedWithCurrentItem. ListView refreshes as expected.
// the XAML
<TreeView DockPanel.Dock="Left" x:Name="tvwNodes" ItemsSource="{Binding}" SelectedItemChanged="OnNewNodeSelected"/>
<ListView x:Name="lvwProperties" ItemsSource="{Binding Path=Properties}"
// the code-behind
private void OnNewNodeSelected(object sender, RoutedPropertyChangedEventArgs<object> e)
{
lvwProperties.DataContext = tvwNodes.SelectedItem; // this returns the selected Node obj
}