I am having an issue with a directly bound ObservableCollection not updating a StackPanel when new items are added. Any initial items show up correctly. Only items that are added later on fail to display.
XAML:
<ItemsControl x:Name="ImageTable" ItemsSource="{Binding Path=SystemObjectViewItems, Converter={StaticResource UIElementWrapper}}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<ContentPresenter Content="{Binding Path=Value.View}"/>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I am using Prism MVVM so I am binding to my ViewModel which has a property:
public ObservableCollection<SystemObjectViewPresentationModel> SystemObjectViewItems {get; set; }
The basic converter and binding are working as can be demonstrated by the fact that my initial item displays correctly. It’s only items that are added to the collection after initial binding that do not show up.
Any ideas?
Thanks,
Rick
I'm going to take a wild guess and say it's the StaticResource you're using.
If you're not returning an ObservableCollection from it and you're not binding it to watch the original ObservableCollection changes it won't work.
Can you post the code to the converter?
Related
In my WPF App, I want to have several items that are generated by the user on runtime. These are from different classes and hence, my original idea was to add them to different Observable Collections and then use them as ItemsSources od different ItemsControls. However, WPF gives me the error System.InvalidOperationException: Items collection must be empty before using ItemsSource. I'm not a WPF expert, but the answer to THIS SO question seems to indicate that I can only have 1 ItemsControl.
THIS SO question indicates that maybe I should use the CompositeCollection Class, but unlike in the cited question, I have several completely different Observable Collections for completely different tasks.
Here is the relevant part of my XAML.CS with two Collections: 1 of a custom Interface type and 1 of custom Class type
public MainWindow()
{
InitializeComponent();
DefaultWindowDefinition.ItemsSource = ProcessElements = new ObservableCollection<IProcessSimulator>();
PathControl.ItemsSource = PathElements = new ObservableCollection<VisualPath>();
}
And here is the relevant part of the XAML I tried to use:
<Grid x:Name="MainGrid"
Background="{StaticResource Alternating}"
MouseLeftButtonUp="grid_MouseLeftButtonUp"
ShowGridLines="True">
<ItemsControl Name="DefaultWindowDefinition"
ItemsSource="{Binding ProcessElements}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<!--HERE IS A LONG LIST OF ELEMENTS-->
</DataTemplate>
</ItemsControl.ItemTemplate>
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<!--TEMPLATE FOR THE 1ST ITEMSCONTROL-->
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemContainerStyle>
<Style>
<!--STYLE PROPERTIES FOR THE 1ST ITEMSCONTROL-->
</Style>
</ItemsControl.ItemContainerStyle>
</ItemsControl>
<ItemsControl Name="PathControl"
ItemsSource="{Binding PathElements}">
<DataTemplate>
<!--HERE IS A LIST OF OTHER TYPE OFELEMENTS-->
</DataTemplate>
</ItemsControl>
</Grid>
How should I approach this problem or rather, what C#/WPF element should I use? A reference and some words of simple explanation is more than enough, I can google the rest myself, I just don't know, what to look for really.
You should set the ItemTemplate property of the "PathControl" to your DataTemplate:
<ItemsControl Name="PathControl" ItemsSource="{Binding PathElements}">
<ItemsControl.ItemTemplate> <!-- NOTE THIS -->
<DataTemplate>
<!--HERE IS A LIST OF OTHER TYPE OFELEMENTS-->
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
If you omit the <ItemsControl.ItemTemplate> element, you are adding a DataTemplate to the Items collection of the ItemsControl and you can't also set its ItemsSource property.
Trying to do so will results in an System.InvalidOperationException exception being thrown with the error message you are getting.
It is perfectly fine for several ItemsControl to bind to the same source collection.
It seems like you are setting the ItemsSource twice. Once in the code behind and once in the XAML. Remove the code behind that sets the Items source and just initialize the observable collections. The XAML should take care of binding to the collections.
I'm trying to add buttons dynamically and it's work but command doesn't work.
I'm getting error
ItemTemplate and ItemTemplateSelector are ignored for items already of the ItemsControl's container type; Type='RadRibbonButton'
<telerik:RadRibbonGroup>
...
<telerik:RadRibbonGroup.DataContext>
<vm:Group1/>
</telerik:RadRibbonGroup.DataContext>
<ItemsControl ItemsSource="{Binding ButtonsCollection}" >
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Button Content="{Binding}" Command="{Binding DataContext.ButtonCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type telerik:RadRibbonGroup}}}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</telerik:RadRibbonGroup>
ButtonCommand= new DelegateCommand(ExecuteCommand);
private void ExecuteCommand()
{
...
}
Check that it does reach the command in debug mode.
Is your ButtonsCollection is dependency property? do you raise its change?
You are not supposed to add actual buttons to your buttons collection, thats is not pure mvvm. you need to create the buttons in a data template, and in the collection you need to create the properties like the button's content etc.
If you still insist creating actual buttons, i think that templating "" won't work. Try "
It doesn't reach
ObservableCollection of buttons(and I can see the buttons in the view)
3.I should create and add buttons to collection runtime(There are special logic behind this).In constructor I create command
I am a bit baffled here. I have a List<BitmapImage> in a Viewmodel that is populating. I am trying to display the list on the view with an ItemsControl, but the Images don't show up. Oddly, I can access the same collection and get an image to display if I am using an Image tag.
<ItemsControl ItemsSource="{Binding Path=Images}" MinHeight="80">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Image Source="{Binding}" MinWidth="80" MinHeight="80" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
<Image HorizontalAlignment="Left" Name="image1" Stretch="Uniform" VerticalAlignment="Top" Source="{Binding Path=Images[0]}" MinHeight="80" MaxHeight="200" />
Note that they both point to Images. The Image shows up, the ItemsControl stays empty. What is going on?
You'll solve this by using an ObservableCollection as opposed to a List. The ItemsControl isn't going to rebind on the change notification of a List. You won't have to worry about explicitly calling the change notification for the List either if you use an ObservableCollection.
I was able to replicate your scenario and simply using an ObservableCollection solves the issue. As to why: http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx
Specifically, see this quote in the Remarks section:
For change notification to occur in a binding between a bound client and a data source, your bound type should either: Implement the INotifyPropertyChanged interface (preferred). Provide a change event for each property of the bound type. Do not do both.
All,
I'm pounding my head against the wall here. What I need is simple, and I'm sure there is a simple answer, but I can't seem to find it.
Situation: I have a Silver light 4.0 app and I'm currently binding a list of strings to an Items control. In the data template for that I have a simple text box that I was doing very basic Binding "{Binding}". I need to update the binding to be twoway so the edits are automatically pushed back to my datacontext.
Here is the Items control before I update the binding:
<ItemsControl x:Name="spLiftHeader" ItemsSource="{Binding Path=WeekLabels}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel x:Name="spLiftHeader" Orientation="Horizontal" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
**<TextBox x:Name="txtWeekLbl" Text="{Binding}" Foreground="Black" Width="125" TextAlignment="Center"/>**
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Here is the items control after the binding change:
<ItemsControl x:Name="spLiftHeader" ItemsSource="{Binding Path=WeekLabels}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel x:Name="spLiftHeader" Orientation="Horizontal" />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
**<TextBox x:Name="txtWeekLbl" Text="{Binding Mode=TwoWay}" Foreground="Black" Width="125" TextAlignment="Center"/>**
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
I've just simply added the "Mode=TwoWay" to the binding.
After updating that, I get the amazingly useless error 4004
"System.Windows.Markup.XamlParseException: Provide value on 'System.Windows.Data.Binding' threw an exception" and the Line/Position reference points right do my updated Binding.
How does one add the Two Way mode to the simple binding?
Thanks in advance.
Nick
Two-way binding to an entire object (a string in this case) makes no sense to Silverlight so it is correct to throw an exception. Shame it is not a more useful error message :)
When there is no Path in the binding the ItemsControl can fetch a value using Object.ToString(), but where will it store the result back? It can't replace the string as that would require placing a new string object back in the collection. Two-way binding is done via reflection against a property of an object.
Instead of a simple list of strings, use a list of some new object that contains a string property and explicitly bind to that property. It will make everything a lot easier. (Make sure your new class and property implement INotifyPropertyChanged).
I am not 100% sure, but I don't think the the Mode=TwoWay should be set in the TextBox itself.
If that doesn't work, try it on both. However, in either case do not use List<T> as a data source behind that items control. Lists do not fire changed event when one of its items has changed. Use ObservableCollection<T> (from the System.Collections.ObjectModel namespace) instead of the List<T>
I have a list of AvailableItems that I want to display as a list of checkboxes, so that users can pick which items to generate, which are then stored in another list called ItemsToGenerate (my lists are actually just lists of strings).
Showing all available items with corresponding checkboxes is easy:
<ItemsControl ItemsSource="{Binding Path=AvailableItems}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
But now I need to bind each Checkbox.IsChecked property, to the fact that the item is in the ItemsToGenerate list. I thought of making a ListContainmentToBoolConverter like this:
IsChecked="{Binding Path=ItemsToGenerate,
Converter={StaticResource ListContainmentToBoolConverter}}"
But that doesn't work because I'm missing a ConverterParameter to pass the value of each item, but I can't do that, because ConverterParameter does not support binding.
Any ideas?
I've found a solution to my problem.
I've changed my ItemsControl to a ListBox, and added a binding between the SelectedItems with my ItemsToGenerate collection using the technique described here. It basically allows me to synchronize any custom collection to ListBox.SelectedItems using a simple attached property.
<ListBox ItemsSource="{Binding AvailableItems}"
Behaviors:MultiSelectorBehaviours.SynchronizedSelectedItems=
"{Binding ItemsToGenerate}"
SelectionMode="Multiple"
Background="{x:Null}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<WrapPanel />
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding}"
Margin="3"
IsChecked="{Binding RelativeSource=
{RelativeSource Mode=FindAncestor,
AncestorType={x:Type ListBoxItem}},
Path=IsSelected}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ListBox>
I'm still able to display this as I initially wanted (a list of checkboxes), by adding a data template to change each ListBoxItem to a checkbox and binding each Checkbox.IsChecked to ListBoxItem.IsSelected.
I had this pattern in so many places in my application that this is the ideal solution for me, because now I just need to specify one attached property, and the rest is all handled by the data bindings, and I don't need any additional code.
I honestly would create a list of objects containing both the string and a boolean indicating if it is checked.
With a little Linq you can generate your list of objects and bind it to itemSource instead of binding the list of strings.
It will be simpler in the end, especially if you actually need to update something if the user is allowed to check/uncheck the checkboxes.
== update ==
in answer to the comment, my take on this because I'm not sure I understand what the actual problem would be: provided we have the full list (AvailableItems) and the list of selected items (ItemsToGenerate):
public class ItemEntry
{
public string Name { get; set; }
public bool IsSelected {get; set; }
}
...
_Items = from item in AvailableItems
select new ItemEntry() {
Name = item,
IsSelected = ItemsToGenerate.contains(item)
}).ToList();
You can then bind your list like so, by exposing _Items as a property named Items:
<ItemsControl ItemsSource="{Binding Path=Items}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<CheckBox Content="{Binding Name}" IsChecked="{Binding IsSelected}" />
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
You can at a later time select from _Items where IsSelected is true to get the selected items if you need to.
Also, if ItemsToGenerate can get big, you should create a HashSet of the values and use it in the query, that should make it faster if need be.