I am trying to find out how to set correctly multiple DataContexts in XAML page. I have a basic collection that I create in code behind and set ItemSource Binding og AutoCompleteBox to it. At the same time, I have another datacontext to set labelsDataSource inside the grid. If I set this datacontext, the AutoCompleteBox’s itemsSource binding is lost. AutoCompleteBox is inside that grid. I do assign DataContext directly to the objetc this way:
MyAutoCompleteBox.DataContext = this;
I am wondering if there is a better way to do it?
Thank you in advance for the help!
Setting AutoComplete Box:
<sdk:AutoCompleteBox x:Name="MyAutoCompleteBox" IsTextCompletionEnabled="True" ItemsSource="{Binding Items}" />
Code Behind:
public IList<string> Items
{
get;
private set;
}
public Basic_ChildWindow()
{
InitializeComponent();
Items = new List<string>();
Items.Add(#"One");
Items.Add(#"Two");
Items.Add(#"Three");
DataContext = this;
}
Another datacontext in the same XAML page, AutoCompleteBox is inside that grid:
<Grid x:Name="grdBasic_ChildWindow_Right" Style="{StaticResource GridStyle}" DataContext="{Binding Source={StaticResource LabelsDataSource}}">
I'm not sure I understand your question--what is "labelsDataSource"?
However, if what you have posted is all the code and there is nothing more to it, simply remove the datacontext/binding from the grid. The grid does not need a datacontext set (it is simply a visual container--not data-related).
So change this:
<Grid x:Name="grdBasic_ChildWindow_Right" Style="{StaticResource GridStyle}" DataContext="{Binding Source={StaticResource LabelsDataSource}}">
To this:
<Grid x:Name="grdBasic_ChildWindow_Right" Style="{StaticResource GridStyle}">
Related
Sorry, XAML is new for me, so I apologize in advance if I sound like a noob.
I have items in the ListBox being dynamically added/deleted/etc, it is bound like so:
<ListBox Name="missionList" ItemsSource="{Binding Mode=OneWay}" ItemTemplate="{DynamicResource missionLegTemplate}" SelectionChanged="missionList_SelectionChanged"/>
The items it is bound to are contained in a list that inherits from ObservableList. This list is my DataContext which is set at the start of the program:
public MainWindow()
{
InitializeComponent();
DataContext = new MissionList();
}
I have a series of text boxes which are intended to be used both to display current values of the object properties and save them as they are edited.
After reading around, I am getting the impression that I need to set the DataContext in the scope of the text boxes to the currently selected object in the ListBox, but I'm not sure how to access that object with XAML.
Does that make sense? Thanks in advance for the help!
I would probably move your MissionList into a ViewModel class, along with a new property for SelectedMission that can be bound to the ListBox's SelectedItem.
As an example (not necessarily working code):
public MainWindow()
{
InitializeComponent();
DataContext = new MainWindowViewModel();
}
public class MainWindowViewModel
{
public ObservableCollection<Mission> MissionList { ... }
public Mission SelectedMission { ... }
.
.
.
}
<ListBox ItemsSource="{Binding MissionList}" SelectedItem="{Binding SelectedMission}" />
<TextBox Text="{Binding Path=SelectedMission.SomeTextField, Mode=OneWay}" />
This question is a "sequel" to this question (I have applied the answer, but it still won't work).
I'm trying to create an extended ToolBar control for a modular application, which can load its items from multiple data sources (but that is not the issue I'm trying to solve right now, now I want it to work when used as regular ToolBar found in WPF).
In short: I want the ToolBar's items to be able to bind to the tb:ToolBar's parents.
I have following XAML code:
<Window Name="myWindow" DataContext="{Binding ElementName=myWindow}" >
<DockPanel>
<tb:ToolBar Name="toolbar" DockPanel.Dock="Top" DataContext="{Binding ElementName=myWindow}>
<tb:ToolBar.Items>
<tb:ToolBarControl Priority="-3">
<tb:ToolBarControl.Content>
<StackPanel Orientation="Horizontal">
<TextBlock>Maps:</TextBlock>
<ComboBox ItemsSource="{Binding SomeProperty, ElementName=myWindow}">
Some info about the types:
tb:ToolBar is an UserControl with dependency property Items of type FreezableCollection<ToolBarControl>.
tb:ToolBarControl is an UserControl with template pretty much identical to ContentControl's template.
The problem is that the binding in the ComboBox fails (with the usual "Cannot find source for binding with reference"), because its DataContext is null.
Why?
EDIT: The core of the question is "Why is the DataContext not inherited?", without it, the bindings can't work.
EDIT2:
Here is XAML for the tb:ToolBar:
<UserControl ... Name="toolBarControl">
<ToolBarTray>
<ToolBar ItemsSource="{Binding Items, ElementName=toolBarControl}" Name="toolBar" ToolBarTray.IsLocked="True" VerticalAlignment="Top" Height="26">
EDIT 3:
I posted an example of what works and what doesn't: http://pastebin.com/Tyt1Xtvg
Thanks for your answers.
I personally don't like the idea of setting DataContext in controls. I think doing this will somehow break the data context inheritance. Please take a look at this post. I think Simon explained it pretty well.
At least, try removing
DataContext="{Binding ElementName=myWindow}"
from
<tb:ToolBar Name="toolbar" DockPanel.Dock="Top" DataContext="{Binding ElementName=myWindow}>
and see how it goes.
UPDATE
Actually, keep all your existing code (ignore my previous suggestion for a moment), just change
<ComboBox ItemsSource="{Binding SomeProperty, ElementName=myWindow}">
to
<ComboBox ItemsSource="{Binding DataContext.SomeProperty}">
and see if it works.
I think because of the way you structure your controls, the ComboBox is at the same level/scope as the tb:ToolBarControl and the tb:ToolBar. That means they all share the same DataContext, so you don't really need any ElementName binding or RelativeSource binding to try to find its parent/ancestor.
If you remove DataContext="{Binding ElementName=myWindow} from the tb:ToolBar, you can even get rid of the prefix DataContext in the binding. And this is really all you need.
<ComboBox ItemsSource="{Binding SomeProperty}">
UPDATE 2 to answer your Edit 3
This is because your Items collection in your tb:ToolBar usercontrol is just a property. It's not in the logical and visual tree, and I believe ElementName binding uses logical tree.
That's why it is not working.
Add to logical tree
I think to add the Items into the logical tree you need to do two things.
First you need to override the LogicalChildren in your tb:ToolBar usercontrol.
protected override System.Collections.IEnumerator LogicalChildren
{
get
{
if (Items.Count == 0)
{
yield break;
}
foreach (var item in Items)
{
yield return item;
}
}
}
Then whenever you added a new tb:ToolBarControl you need to call
AddLogicalChild(item);
Give it a shot.
This WORKS...
After playing around with it a little bit, I think what I showed you above isn't enough. You will also need to add these ToolBarControls to your main window's name scope to enable ElementName binding. I assume this is how you defined your Items dependency property.
public static DependencyProperty ItemsProperty =
DependencyProperty.Register("Items",
typeof(ToolBarControlCollection),
typeof(ToolBar),
new FrameworkPropertyMetadata(new ToolBarControlCollection(), Callback));
In the callback, it is where you add it to the name scope.
private static void Callback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var toolbar = (ToolBar)d;
var items = toolbar.Items;
foreach (var item in items)
{
// the panel that contains your ToolBar usercontrol, in the code that you provided it is a DockPanel
var panel = (Panel)toolbar.Parent;
// your main window
var window = panel.Parent;
// add this ToolBarControl to the main window's name scope
NameScope.SetNameScope(item, NameScope.GetNameScope(window));
// ** not needed if you only want ElementName binding **
// this enables bubbling (navigating up) in the visual tree
//toolbar.AddLogicalChild(item);
}
}
Also if you want property inheritance, you will need
// ** not needed if you only want ElementName binding **
// this enables tunneling (navigating down) in the visual tree, e.g. property inheritance
//protected override System.Collections.IEnumerator LogicalChildren
//{
// get
// {
// if (Items.Count == 0)
// {
// yield break;
// }
// foreach (var item in Items)
// {
// yield return item;
// }
// }
//}
I have tested the code and it works fine.
I took the pieces of Xaml that you posted and tried to reproduce your problem.
The DataContext seems to be inheriting just fine from what I can tell. However, ElementName Bindings fail and I think this has to do with the fact that even though you add the ComboBox in the Window, it ends up in a different scope. (It is first added to the Items property of the custom ToolBar and is then populated to the framework ToolBar with a Binding)
A RelativeSource Binding instead of an ElementName Binding seems to be working fine.
But if you really want to use the name of the control in the Binding, then you could check out Dr.WPF's excellent ObjectReference implementation
It would look something like this
<Window ...
tb:ObjectReference.Declaration="{tb:ObjectReference myWindow}">
<!--...-->
<ComboBox ItemsSource="{Binding Path=SomeProperty,
Source={tb:ObjectReference myWindow}}"
I uploaded a small sample project where both RelativeSource and ObjectReference are succesfully used here: https://www.dropbox.com/s/tx5vdqlm8mywgzw/ToolBarTest.zip?dl=0
The custom ToolBar part as I approximated it looks like this in the Window.
ElementName Binding fails but RelativeSource and ObjectReference Bindings work
<Window ...
Name="myWindow"
tb:ObjectReference.Declaration="{tb:ObjectReference myWindow}">
<!--...-->
<tb:ToolBar x:Name="toolbar"
DockPanel.Dock="Top"
DataContext="{Binding ElementName=myWindow}">
<tb:ToolBar.Items>
<tb:ContentControlCollection>
<ContentControl>
<ContentControl.Content>
<StackPanel Orientation="Horizontal">
<TextBlock>Maps:</TextBlock>
<ComboBox ItemsSource="{Binding Path=StringList,
ElementName=myWindow}"
SelectedIndex="0"/>
<ComboBox ItemsSource="{Binding Path=StringList,
Source={tb:ObjectReference myWindow}}"
SelectedIndex="0"/>
<ComboBox ItemsSource="{Binding Path=StringList,
RelativeSource={RelativeSource AncestorType={x:Type Window}}}"
SelectedIndex="0"/>
</StackPanel>
</ContentControl.Content>
</ContentControl>
</tb:ContentControlCollection>
</tb:ToolBar.Items>
</tb:ToolBar>
Often if there is no DataContext then ElementName will not work either. One thing which you can try if the situation allows it is using x:Reference.
For that you need to move the bound control into the resources of the referenced control, change the binding and use StaticResource in the place where it was, e.g.
<Window Name="myWindow" DataContext="{Binding ElementName=myWindow}" >
<Window.Resources>
<ComboBox x:Key="cb"
ItemsSource="{Binding SomeProperty,
Source={x:Reference myWindow}}"/>
</Window.Resources>
<DockPanel>
<tb:ToolBar Name="toolbar" DockPanel.Dock="Top" DataContext="{Binding ElementName=myWindow}>
<tb:ToolBar.Items>
<tb:ToolBarControl Priority="-3">
<tb:ToolBarControl.Content>
<StackPanel Orientation="Horizontal">
<TextBlock>Maps:</TextBlock>
<StaticResource ResourceKey="cb"/>
The proper answer is probably to add everything to the logical tree as mentioned in previous answers, but the following code has proved to be convenient for me. I can't post all the code I have, but...
Write your own Binding MarkupExtension that gets you back to the root element of your XAML file. This code was not compiled as I hacked up my real code to post this.
[MarkupExtensionReturnType(typeof(object))]
public class RootBindingExtension : MarkupExtension
{
public string Path { get; set; }
public RootElementBinding(string path)
{
Path = path;
}
public override object ProvideValue(IServiceProvider serviceProvider)
{
IRootObjectProvider rootObjectProvider =
(IRootObjectProvider)serviceProvider.GetService(typeof(IRootObjectProvider));
Binding binding = new Binding(this.Path);
binding.Source = rootObjectProvider.RootObject;
// Return raw binding if we are in a non-DP object, like a Style
if (service.TargetObject is DependencyObject == false)
return binding;
// Otherwise, return what a normal binding would
object providedValue = binding.ProvideValue(serviceProvider);
return providedValue;
}
}
Usage:
<ComboBox ItemsSource={myBindings:RootBinding DataContext.SomeProperty} />
I've got a custom WPF control with a DependencyProperty MyString
I'm using the control within an ItemsControl on my View and want to fish a value out from the ViewModel.
As the DataContext of the control becomes each Item in the ItemsSource of the ItemsControl I thought I'd just be able to use FindAncestor but it dosnt seem to work ... can anyone see where I'm going wrong please?
Heres the XAML on the View ...
<Grid>
<ItemsControl ItemsSource="{Binding MyItems}" >
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal" Name="myStack">
<ImportExceptions:ControlStrip MyString="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ItemsControl}}, Path=DataContext.MyStringOnViewModel}" />
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
and heres the code behind my custom control where I've set up my dependency property ...
public partial class ControlStrip
{
public ControlStrip()
{
InitializeComponent();
}
public string MyString
{
get
{
return GetValue(MyStringProperty).ToString();
}
set
{
SetValue(MyStringProperty, value);
}
}
public static readonly DependencyProperty MyStringProperty =
DependencyProperty.RegisterAttached("MyString", typeof (string), typeof (ControlStrip));
}
The DataContext of the control doesn't change - the DataContext for the ImportExceptions:ControlStrip will be (unless explicitly specified) the next DataContext available as its goes 'up' the visual tree...
I infer from your code that you have set the DataContext of the View to a ViewModel with properties 'MyItems' and 'MyStringOnViewModel' - you should be able to simply bind the MyString property directly to the ViewModel, like
<ImportExceptions:ControlStrip MyString="{Binding Path=MyStringOnViewModel}" />
Your code looks fine. Probably you have made an error in the DataContext reference. In all likeliness the DataContext of the the ItemsControl already is MyStringOnViewModel. So, omit the .MystringOnViewModel after the DataContext in the Path attribute. If not can you give some more code, ore post a simplification of it that mimicks how the DataCon,text(s) is/are set?
I have a ViewModel (AbstractContextMenu) that represents my context menu (IContextMenu), and I bind a real ContextMenu to it with a DataTemplate:
<DataTemplate DataType="{x:Type local:AbstractContextMenu}">
<ContextMenu x:Name="contextMenu"
ItemsSource="{Binding Path=(local:IContextMenu.Items)}"
IsEnabled="{Binding Path=(local:IContextMenu.IsEnabled)}"/>
</DataTemplate>
Then I have a dummy ConcreteContextMenu for testing that just inherits from AbstractContextMenu. AbstractContextMenu just implements this interface:
public interface IContextMenu : IExtension
{
IEnumerable<IMenuItem> Items { get; set; }
bool IsEnabled { get; set; }
}
I'm using it as a property of another ViewModel object:
public IContextMenu ContextMenu
{
get
{
return m_ContextMenu;
}
protected set
{
if (m_ContextMenu != value)
{
m_ContextMenu = value;
NotifyPropertyChanged(m_ContextMenuArgs);
}
}
}
private IContextMenu m_ContextMenu = new ConcreteContextMenu();
static readonly PropertyChangedEventArgs m_ContextMenuArgs =
NotifyPropertyChangedHelper.CreateArgs<AbstractSolutionItem>(o => o.ContextMenu);
Then I bind a StackPanel to that ViewModel and bind the ContextMenu property on the StackPanel to the ContextMenu property of the ViewModel:
<StackPanel Orientation="Horizontal"
ContextMenu="{Binding Path=(local:AbstractSolutionItem.ContextMenu)}"
ContextMenuOpening="stackPanel_ContextMenuOpening">
<!-- stuff goes in here -->
</StackPanel>
When I run this, the ContextMenuOpening event on the StackPanel is fired, but the ContextMenu is never displayed. I'm not sure if I can even do this (apply a ContextMenu to a ContextMenu ViewModel using a DataTemplate). Anyone know?
What is the type of AbstractSolutionItem.ContextMenu? If it corresponds to the ContextMenu property in your question, then the problem could be that the type is wrong. The ContextMenu property of FrameworkElement is expecting an actual ContextMenu, not an IContextMenu. Try checking the output window while debugging your app - you might get an error message stating that this is the problem.
Instead of using a DataTemplate to define your ContextMenu, just put the contents of the template StackPanel.ContextMenu:
<StackPanel Orientation="Horizontal"
ContextMenu="{Binding Path=(local:AbstractSolutionItem.ContextMenu)}"
ContextMenuOpening="stackPanel_ContextMenuOpening">
<StackPanel.ContextMenu DataContext="{Binding Path=(local:AbstractSolutionItem.ContextMenu)}">
<ContextMenu x:Name="contextMenu"
ItemsSource="{Binding Path=Items}"
IsEnabled="{Binding Path=IsEnabled}"/>
</StackPanel.ContextMenu>
<!-- stuff goes in here -->
</StackPanel>
That should get you most of the way there. However, there is still a problem since the ContextMenu does not know how to create a MenuItem from an IMenuItem. To solve this, create an ItemTemplate for the ContextMenu, which binds members of IMenuItem to `MenuItem.
Could you shed some light on the syntax used in the ItemsSource property in the DataTemplate ? Using parentheses usually means an attached property. And Items does not seem to be an attached property defined by IContextMenu (as an interface cannot define such a property).
The DataTemplate is linked to an object of type AbstractContextMenu which has a property called Items. So, the DataTemplate could simply reference it like this:
<DataTemplate DataType="{x:Type local:AbstractContextMenu}">
<ContextMenu x:Name="contextMenu"
ItemsSource="{Binding Path=Items)}"
IsEnabled="{Binding Path=IsEnabled}"/>
</DataTemplate>
If the AbstractSolutionItem class is the VM of the StackPanel, you could bind it like this:
<StackPanel Orientation="Horizontal"
ContextMenu="{Binding Path=ContextMenu}"
ContextMenuOpening="stackPanel_ContextMenuOpening">
<!-- stuff goes in here -->
</StackPanel>
Of course, the DataTemplate must be "accessible" from the StackPanel.
Bind the ContextMenu property of your view (StackPanel in this scenario) to the ContextMenu property of your ViewModel and provide a IValueConverter to the binding that will create the ContextMenu object and set the IContextMenu to it's DataContext.
I'm trying to bind two ListBoxes:
<ListBox SelectionChanged="lbApplications_SelectionChanged"
ItemsSource="{Binding Path=Applications,
UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />
<ListBox DisplayMemberPath="Message"
ItemsSource="{Binding Path=Events,
UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />
Applications and Events are public properties in Window class.
I set DataContext to this to both list boxes and implement INotifyPropertyChanged in Window class:
private void NotifyPropertyChanged(string info)
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs(info));
}
And then after adding new item to Applications or Events I call:
NotifyPropertyChanged("Events");
NotifyPropertyChanged("Applications");
The issue is that ListBox is loaded only one time. What am I doing wrong?
Let's just look at one of the ListBoxes, since they're both the same, basically.
The code we're concerned about is this:
<ListBox ItemsSource="{Binding Path=Applications,
UpdateSourceTrigger=PropertyChanged, Mode=OneWay}" />
Since you're new to WPF, let me say you probably don't need UpdateSourceTrigger or Mode in there, which leaves us with this:
<ListBox ItemsSource="{Binding Path=Applications}" />
You mentioned that Applications is a public property in your code-behind. You need it to be a DependencyProperty, and you need it to fire events when it changes -- most people use an ObservableCollection for this.
So your code-behind will have something like this:
public ObservableCollection<string> Applications
{
get { return (ObservableCollection<string>)GetValue(ApplicationsProperty); }
set { SetValue(ApplicationsProperty, value); }
}
public static readonly DependencyProperty ApplicationsProperty =
DependencyProperty.Register("Applications",
typeof(ObservableCollection<string>), typeof(Window1),
new UIPropertyMetadata(null));
Then, where you want to add it, you'll do something like this:
this.Applications = new ObservableCollection<string>();
Applications.Add("Whatever");
Finally, for the "simple" binding syntax to work in the XAML, I usually change the DataContext in my Window (or the root Control element for the file, whatever I'm working in) to
<Window DataContext="{Binding RelativeSource={RelativeSource Self}}" ... >
...
Your Applications box will update automatically.
The problem is that your property value hasn't changed. It's still the same list, same reference.
One solution might be that your collections are of type ObservableCollection. These lists provide events for WPF when you add or remove items.