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.
Related
I'm building a control that can edit POCOs. There is a descriptor collection for the fields within the POCO that need to be edited and I'm binding a ListBox's ItemsSource to this collection. Amongst other things, the descriptor gives me the ability to select a suitable DataTemplate and the variable name in the POCO that this ListBox item should edit.
My ListBox is built like this:
<ListBox ItemsSource="{Binding ColumnCollection, ElementName=root}">
<ListBox.Resources>
<DataTemplate x:Key="TextTemplate">
<StackPanel>
<TextBlock Text="{Binding DisplayName}" />
<!-- !!! Question about following line !!! -->
<TextBox Text="{Binding ElementName=vm.CurentEditing, Path=PathName}" />
</StackPanel>
</DataTemplate>
<!-- Details omitted for brevity -->
<DataTemplate x:Key="PickListTemplate" />
<DataTemplate x:Key="BooleanTemplate" />
</ListBox.Resources>
<ListBox.ItemTemplateSelector>
<local:DataTypeSelector
TextTemplate="{StaticResource TextTemplate}"
PickListTemplate="{StaticResource PickListTemplate}"
BooleanTemplate="{StaticResource BooleanTemplate}"
/>
</ListBox.ItemTemplateSelector>
</ListBox>
It is the TextBox binding expression in the "TextTemplate" that I am having problems with. The problem is that "PathName" should not be taken as a literal string, but is the name of a string property in the ColumnDescription class (the collection type of ColumnCollection used for ListBox.ItemsSource), which gives the name of the POCO property I want to bind to (the POCO is "vm.CurrentEditing").
Is there some way to use the value of a property in XAML as input to a binding expression, or will I have to resort to code behind?
(Incidentally, specifying the ElementName as "x.y" as I have done above also seems to be invalid. I assume the "y" part should be in Path but that's currently taken up with my property name...!)
So you want to bind TextBox.Text to Property X of Object Y, where X and Y both change at runtime.
It sounds like what you want to do is something analogous to ListBox.DisplayMemberPath: You can bind a string or PropertyPath property to DisplayMemberPath and it'll work. The way I've done stuff like that is to have a dependency property of type String or PropertyPath, and programatically create a binding from that to whatever property.
So, I wrote an attached property which creates a binding.
public class POCOWrangler
{
#region POCOWrangler.BindPropertyToText Attached Property
public static String GetBindPropertyToText(TextBox obj)
{
return (String)obj.GetValue(BindPropertyToTextProperty);
}
public static void SetBindPropertyToText(TextBox obj, PropertyPath value)
{
obj.SetValue(BindPropertyToTextProperty, value);
}
public static readonly DependencyProperty BindPropertyToTextProperty =
DependencyProperty.RegisterAttached("BindPropertyToText", typeof(String), typeof(POCOWrangler),
new PropertyMetadata(null, BindPropertyToText_PropertyChanged));
private static void BindPropertyToText_PropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (e.NewValue is String && d is TextBox)
{
var tb = d as TextBox;
var binding = new Binding((String)e.NewValue);
// The POCO object we're editing must be the DataContext of the TextBox,
// which is what you've got already -- but don't set Source explicitly
// here. Leave it alone and Binding.Source will be updated as
// TextBox.DataContext changes. If you set it explicitly here, it's
// carved in stone. That's especially a problem if this attached
// property gets initialized before DataContext.
//binding.Source = tb.DataContext;
binding.Mode = BindingMode.TwoWay;
BindingOperations.SetBinding(tb, TextBox.TextProperty, binding);
}
}
#endregion POCOWrangler.BindPropertyToText Attached Property
}
And I wrote a quick example thing: There's a little class named Foo that has a Name property, and a viewmodel with two properties, Foo Foo and String DisplayPathName. It works! Of course, this depends on default TextBox editing behavior for whatever type the property happens to be. I think that will get you the same results as if you'd bound explicitly in XAML, but it sitll won't always necessarily be just what you want. But you could very easily go a little nuts and add some triggers in the DataTemplate to swap in different editors, or write a DataTemplateSelector.
I stuffed ViewModel.Foo in a ContentControl just to get a DataTemplate into the act, so that the TextBox gets his DataContext in the same manner as yours.
Note also that I'm getting DisplayPathName by a relative source from something outside the DataContext object -- it's not a member of Foo, of course, it's a member of the viewmodel.
C#
public MainWindow()
{
InitializeComponent();
DataContext = new ViewModel {
DisplayPathName = "Name",
Foo = new Foo { Name = "Aloysius" }
};
}
XAML
<ContentControl
Content="{Binding Foo}"
>
<ContentControl.ContentTemplate>
<DataTemplate>
<TextBox
local:POCOWrangler.BindPropertyToText="{Binding
DataContext.DisplayPathName,
RelativeSource={RelativeSource AncestorType=ContentControl}}"
/>
</DataTemplate>
</ContentControl.ContentTemplate>
</ContentControl>
That was fun.
I'm having some issues with binding some custom controls in a Windows Phone app right now. Usually this is never an issue but apparently my mind can't comprehend this today.
So I'm doing an MVVM style setup which is good. I have my page with a view and also a viewmodel. Now on a WebClient callback I assign the dataContext of my view to the list of models in my ViewModel, nice and simple thus far...now in my view I created a ListBox with a custom control in the datatemplate which is basically a cell in the list. I once again set my user controls dataContext to binding, and binding all the models values to the regular UI elements works no problem.
Here's a sample:
<Grid Grid.Column="0">
<Image Source="{Binding SmallPath}" VerticalAlignment="Top"/>
</Grid>
<Grid Grid.Column="1">
<StackPanel Margin="12,0,0,0">
<TextBlock x:Name="MemberId_TextBlock" Text="{Binding MemberId}" FontSize="28"
Margin="0,-8,0,0"
Foreground="{StaticResource PhoneForegroundBrush}"/>
<StackPanel Orientation="Horizontal" Margin="0,-11,0,0">
<TextBlock Text="{Binding DaysReported}" FontSize="42"
Margin="0,0,0,0"
Foreground="{StaticResource PhoneAccentBrush}"/>
<TextBlock Text="days" FontSize="24"
Margin="3,19,0,0"
Foreground="{StaticResource PhoneSubtleBrush}"/>
</StackPanel>
</StackPanel>
</Grid>
That's in my user control, and here's the the view where the usercontrol is housed:
<Grid x:Name="LayoutRoot" Background="Transparent">
<ListBox Name="TopSpotter_ListBox" ItemsSource="{Binding}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<!--<TextBlock Text="{Binding MemberId}"/>-->
<controls:TopSpotterItemControl DataContext="{Binding}"/>
<Grid Height="18"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
Now this is good enough but what I want to do in my view is set data from my model like Booleans that determine whether or not I should show certain Grids etc. So if I try to set a dependency property explicitly in my control it fires and will run logic in the Getter/Setters for instance. HOWEVER if I try to set these custom objects from a binding source it won't actually set.
Here's what works:
<controls:TopSpotterItemControl ChampVisibility="True">
This way will trigger the ChampVisibility property and then in the code behind of the user control I can set visibilities.
Here's what fails but I want to work:
<controls:TopSpotterItemControl ChampVisibility="{Binding IsChamp">
In addition I can still set the DataContext to {Binding} and the result will be unchanged.
In this scenario IsChamp is part of my model that I would like to bind to this user control which I guess comes from the dataContext being set on the view from the viewModel. I'm not sure what I can do to get this so the bindings work etc. without having to set custom properties.
Finally, here's my user control:
public partial class TopSpotterItemControl : UserControl
{
public string MemberId
{
get
{
return this.MemberId_TextBlock.Text;
}
set
{
this.MemberId_TextBlock.Text = value;
}
}
public bool ChampVisibility {
set
{
if (value)
{
this.Champ_Grid.Visibility = System.Windows.Visibility.Visible;
}
}
}
public static readonly DependencyProperty MemberNameProperty =
DependencyProperty.Register("MemberId", typeof(string), typeof(TopSpotterItemControl), new PropertyMetadata(null));
public static readonly DependencyProperty ChampVisibilityProperty =
DependencyProperty.Register("ChampVisibility", typeof(bool), typeof(TopSpotterItemControl), new PropertyMetadata(null));
public TopSpotterItemControl()
{
InitializeComponent();
}
}
Bit long winded and I hope I made things on the issue clear. My one major hang up so far, and I'd like to abstract as much control as I can to the user control via dependency properties explicitly set in xaml, rather than setting up binding in its xaml that depend on the knowledge of a model. Thanks!
Your DependencyProperty is badly formed. (I also don't see Champ_Grid defined in your class or XAML, but I assume that is an ommission)
Setting ChampVisibility = true in code works because it is unrelated to the DependencyProperty.
You can tell easily because the default value for your DP is invalid. It will compile, but the instance constructor will through an exception if it is ever invoked.
new PropertyMetadata(null)
bool = null = exception
If you call GetValue(TopSpotterItemControl.ChampVisibilityProperty) from somewhere you can confirm all of the above.
You should make changes to instance fields in the property changed handler and declare the property like the following, it will work:
Note that the property has to change (not just be set) for the event to be raised.
public bool ChampVisibility
{
get { return (bool)GetValue(ChampVisibilityProperty); }
set { SetValue(ChampVisibilityProperty, value); }
}
public static readonly DependencyProperty ChampVisibilityProperty =
DependencyProperty.Register("ChampVisibility ", typeof(bool), typeof(TopSpotterItemControl), new PropertyMetadata(true, (s, e) =>
{
TopSpotterItemControl instance = s as TopSpotterItemControl;
instance.Champ_Grid.Visibility = instance.ChampVisibility ? System.Windows.Visibility.Visible : System.Windows.Visibility.Collapsed;
}));
Incidentally, your MemberId DependencyProperty is also completely wrong and cannot work.
Note:
The Binding on your TextBox works, because it is binding to the DataContext (your model), so it probably shows the right value.
The Dependency property in your UserControl will never be set though.
Use the propdp code-snippet in Visual Studio so you dont have to concern yourself with the complexities of Dependency Property declaration.
Also check this out for more info about Dependency Properties
How to raise / handle the SelectionChanged event of WPF's ComboBox using the MVVM pattern?
Explain in detail please I am new to WPF.
What I want, is to do some operations when the ComboBox item selection changed. How can I achieve it, in an MVVM way?
MVVM solution:
Bind the ItemsSource and SelectedItem properties of the ComboBox to properties in your ViewModel:
<ComboBox ItemsSource="{Binding MyItems}" SelectedItem="{Binding MySelectedItem}"/>
In MainViewModel.cs:
public ObservableCollection<string> MyItems { get; set; }
private string _mySelectedItem;
public string MySelectedItem
{
get { return _mySelectedItem; }
set
{
// Some logic here
_mySelectedItem = value;
}
}
Code-behind solution:
If you don't want to use MVVM, you can add use this:
<ComboBox SelectionChanged="ComboBox_SelectionChanged" />
And add this in MainWindow.xaml.cs:
private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
// Some logic here
}
I'm a big fan of this method.
xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
<ComboBox Grid.Column="2" DisplayMemberPath="Data.name" ItemsSource="{Binding Model.Regions}" SelectedItem="{Binding Model.SelectedRegion}">
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectionChanged">
<i:InvokeCommandAction Command="{Binding RegionChangedCmd}" />
</i:EventTrigger>
</i:Interaction.Triggers>
</ComboBox>
Your ViewModel needs to implement INotifyPropertyChanged.
public class MyViewModel : INotifyPropertyChanged
{
private string _mySelectedItem;
public string MySelectedItem
{
get
{
return _mySelectedItem;
}
set
{
if (_mySelectedItem != value)
{
_mySelectedItem = value;
// Perform any pre-notification process here.
if (null != PropertyChanged)
{
PropertyChanged(this, new PropertyChangedEventArgs("MySelectedItem"));
}
}
}
}
}
The previously posted XAML is correct:
<ComboBox ItemsSource="{Binding MyItems}" SelectedItem="{Binding MySelectedItem}"/>
Just an enhancement of this solution which exists above, In case you are using Prism Library (if not, then stop reading now, there is nothing for you)
I really like this solution and I think it is better than any other solution, I just want to make a small enhancement to that solution provided by the Prism Library.
that solution is using
<i:InvokeCommandAction Command="{Binding RegionChangedCmd}" />
notice the i: before the InvokeCommandAction. It means that the InvokeCommandAction class exists in the xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity" namespace. This is good and fine, but notice that the Prism library has exactly the same class with the same name InvokeCommandAction. It just exists in another namespace, in the xmlns:prism="http://prismlibrary.com/" namespace.
So actually you can replace the following XAML
<i:InvokeCommandAction Command="{Binding RegionChangedCmd}" />
with this XAML
<prism:InvokeCommandAction Command="{Binding RegionChangedCmd}" />
OK, we can do this, what is the benefit?
To notice the benefit, write the following command in the ViewModel
public ICommand RegionChangedCmd { get; }
public ViewModelConstructor()
{
RegionChangedCmd = new DelegateCommand<SelectionChangedEventArgs>(RegionChangedCmdExecuted);
}
public void RegionChangedCmdExecuted(SelectionChangedEventArgs e)
{
// e parameter is null if you use <i:InvokeCommandAction>
// e parameter is NOT null if you use <prism:InvokeCommandAction>
}
e parameter is null if you use <i:InvokeCommandAction>
e parameter is NOT null if you use <prism:InvokeCommandAction>
As first let's make things clear - you can not change event rather you can subscribe to.
Since you've not provided any information regarding where from you want to handle selection changes I will assume most common scenario - handling in the underlying ViewModel. According to MVVM ViewModel should not know anything about View so you can not subscribe directly from ViewModel to the event of a View's control. But you can bind a property of ViewModel to either SelectedItem or SelectedIndex so it would trigger whilst selection changes.
<ComboBox
SelectedIndex="{Binding SelectedIndexPropertyName}"
... />
There are other solutions doing handling in code behind of a View by accessing a ViewModel via view.DataContext but I would suggest avoid such practice, this are work around cases.
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 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}">