I have this ListBox which is bound to an ObservableCollection. Each object in the list implements an interface called ISelectable
public interface ISelectable : INotifyPropertyChanged
{
event EventHandler IsSelected;
bool Selected { get; set; }
string DisplayText { get; }
}
I want to keep track of which object is selected regardless of how it is selected. The user could click on the representation of the object in the ListBox but it could also be that an object is selected via code. If the user selects an object via the ListBox I cast the the selected item to an ISelectable and set the Selected property to true.
ISelectable selectable = (ISelectable)e.AddedItems[0];
selectable.Selected = true;
My problem is that when I select the object using code I can't get ListBox to change the selected item. I'm using a DataTemplate to show the selected object in a different color which means everything is displayed correctly. But the ListBox has the last object the user clicked as the SelectedItem which means that item can't be clicked without first selecting another object in the list.
Anyone got any idea on how to solve this? I pretty sure I can accomplish what I want by writing some custom code to handle the Mouse and Keyboard events but I rather not. I have tried adding a SelectedItem property to the collection and bind it to the ListBox's SelectItemProperty but no luck.
You could also accomplish this by data binding ListBoxItem.IsSelected to your Selected property. The idea is to set the binding for each of the ListBoxItems as they are created. This can be done using a style that targets each of the ListBoxItems generated for the ListBox.
This way when an item in the ListBox is selected/unselected, the corresponding Selected property will be updated. Likewise setting the Selected property in code will be reflected in the ListBox
For this to work the Selected property must raise the PropertyChanged event.
<List.Resources>
<Style TargetType="ListBoxItem">
<Setter
Property="IsSelected"
Value="{Binding
Path=DataContext.Selected,
RelativeSource={RelativeSource Self}}"
/>
</Style>
</List.Resources>
Have you looked at the list box's SelectedItemChanged and SelectedIndexChanged events?
These should be triggered whenever a selection is changed, no matter how it is selected.
I think you should fire the propertyChanged event when the select has changed. Add this code to the object that implements ISelectable. You'll end up with something like:
private bool _Selected;
public bool Selected
{
get
{
return _Selected;
}
set
{
if (PropertyChanged != null)
PropertyChanged(this, new PropertyChangedEventArgs("Selected"));
_Selected = value;
}
}
I've tried the folowing code:
public ObservableCollection<testClass> tests = new ObservableCollection<testClass>();
public Window1()
{
InitializeComponent();
tests.Add(new testClass("Row 1"));
tests.Add(new testClass("Row 2"));
tests.Add(new testClass("Row 3"));
tests.Add(new testClass("Row 4"));
tests.Add(new testClass("Row 5"));
tests.Add(new testClass("Row 6"));
TheList.ItemsSource = tests;
}
private void Button_Click(object sender, RoutedEventArgs e)
{
tests[3].Selected = true;
TheList.SelectedItem = tests[3];
}
where testClass implements ISelectable.
The is a piece of xaml, nothing fancy:
<ListBox Grid.Row="0" x:Name="TheList"></ListBox>
<Button Grid.Row="1" Click="Button_Click">Select 4th</Button>
I hope this helps.
Related
I have two user controls, one contains a TreeView, one contains a ListView.
The TreeView has an itemsource and hierarchical data templates that fill the nodes and leafes (node=TvShow, leaf=Season).
The ListView should show the children of the selected TreeView item (thus, the selected season): the episodes of that season.
This worked fine when I had both the TreeView and the Listview defined in the same window, I could use something like this:
<ListView
x:Name="_listViewEpisodes"
Grid.Column="2"
ItemsSource="{Binding ElementName=_tvShowsTreeView, Path=SelectedItem.Episodes}">
How can I achieve this, when both controls are defined in separate user controls? (because in the context of one user control, I miss the context of the other user control)
This seems something pretty basic and I am getting frustrated that I can't figure it out by myself. I refuse to solve this with code-behind, I have a very clean MVVM project so far and I would like to keep it that way.
Hope that somebody can give me some advise!
First of all you have to created the SelectedValue proeprty in your ViewModel and bind the TreeView.SelectedItem property to it. Since the SelectedItem property is read-only I suggest you to create a helper to create OneWayToSource-like binding. The code should be like the following:
public class BindingWrapper {
public static object GetSource(DependencyObject obj) { return (object)obj.GetValue(SourceProperty); }
public static void SetSource(DependencyObject obj, object value) { obj.SetValue(SourceProperty, value); }
public static object GetTarget(DependencyObject obj) { return (object)obj.GetValue(TargetProperty); }
public static void SetTarget(DependencyObject obj, object value) { obj.SetValue(TargetProperty, value); }
public static readonly DependencyProperty TargetProperty = DependencyProperty.RegisterAttached("Target", typeof(object), typeof(BindingWrapper), new PropertyMetadata(null));
public static readonly DependencyProperty SourceProperty = DependencyProperty.RegisterAttached("Source", typeof(object), typeof(BindingWrapper), new PropertyMetadata(null, OnSourceChanged));
static void OnSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) {
SetTarget(d, e.NewValue);
}
}
The idea is simple: you have two attached properties, the Source and the Target. When the first one changes the PropertyChangedCallback is called and you simply setting the NewValue as the Target property value. In my opinion this scenario is helpful in a lot of cases when you need to bind the read-only property in XAML (especially in control templates).
I've created a simple model to demonstrate how to use this helper:
public class ViewModel : INotifyPropertyChanged {
public ViewModel() {
this.values = new ObservableCollection<string>()
{
"first",
"second",
"third"
};
}
ObservableCollection<string> values;
string selectedValue;
public ObservableCollection<string> Values { get { return values; } }
public string SelectedValue {
get { return selectedValue; }
set {
if (Equals(selectedValue, values))
return;
selectedValue = value;
if (PropertyChanged == null)
return;
PropertyChanged(this, new PropertyChangedEventArgs("SelectedValue"));
}
}
public event PropertyChangedEventHandler PropertyChanged;
}
So, we have data source, selected value and we'll bind it like this:
<StackPanel>
<TreeView ItemsSource="{Binding Values}"
local:BindingWrapper.Source="{Binding SelectedItem, RelativeSource={RelativeSource Self}, Mode=OneWay}"
local:BindingWrapper.Target="{Binding SelectedValue, Mode=OneWayToSource}"
>
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="Header" Value="{Binding}"/>
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
<TextBlock Text="{Binding SelectedValue}"/>
</StackPanel>
In the TreeView bound to the ItemsSource from the ViewModel I've created two bindings so they are changing the SelectedValue property in your ViewModel. TextBlock in the end of the sample is used just to show that this approach works.
About the very clean MVVM - I think that it is not the same as the "no code-behind". In my sample the ViewModel still doesn't know anything about your view and if you'll use another control to show your data e.g. ListBox you will be able to use the simple two-way binding and the "BindingWrapper" helper will not make your code unreadable or unportable or anything else.
Create a SelectedSeason property in your ViewModel and bind the ListView's ItemsSource to SelectedSeason.Episodes.
In a perfect world, you could now use a Two-Way binding in the TreeView to automatically update this property when the SelectedItem changes. However, the TreeView's SelectedItem property is readonly and cannot be bound. You can use just a little bit of code-behind and create an event handler for the SelectionChanged event of the TreeView to update your ViewModel's SelectedSeason there. IMHO this doesn't violate the the MVVM principles.
If you want a pure XAML solution, that a look at this answer.
I am having a binding update problem with my ComboBox. My ComboBox's ItemSource is bound to a list of LaneConfigurations. The ComboBox's SelectedItem is bound to the SelectedLaneConfiguration property in my code-behind. I configured the ComboBox's ItemTemplate to display the 'DisplayID' property for each LaneConfiguration.
This works most of the time. However, changing a lane configuration can result in the DisplayID changing. If you have a particular lane selected and it's DisplayID is being displayed as the 'Text' of the ComboBox and then you change the LaneConfiguration object, the 'Text' portion of the ComboBox is not updated with the new 'DisplayID' that should be showing. When I click the dropdown arrow on the ComboBox, the item appearing as the selected item in the list is showing the correct DisplayID, but that doesn't match the 'DisplayID' that is being shown at the top of the ComboBox in it's 'Text' field.
In my code behind, I am firing a PropertyChanged event on the 'SelectedLaneConfiguration' property. How do I get the ComboBox to realize that the 'DisplayID' property needs updating? I have tried to fire a PropertyChanged event for the 'DisplayID' property, but it is part of the LaneConfiguration class, so it doesn't appear to be updating.
I have included the XAML below along with a screenshot that shows the ComboBox Text display out of sync with the content of the ComboBox dropdown.
Partial XAML:
<ComboBox x:Name="_comboBoxLanes" Height="26"
ItemsSource="{Binding SensorConfiguration.LaneConfigurations}"
SelectedItem="{Binding Path=SelectedLaneConfiguration}">
<ComboBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding DisplayID, Mode=OneWay}"/>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>
Some of the code-behind:
public partial class LaneManagement : INotifyPropertyChanged, IDisposable
{
..
..
public event PropertyChangedEventHandler PropertyChanged;
private void FirePropertyChanged(string prop)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(prop));
}
}
private void SensorConfiguration_Changed()
{
LaneTools.ResetLanePolygons();
GenerateLaneTypeDropdowns();
FirePropertyChanged("SensorConfiguration");
FirePropertyChanged("SelectedLaneConfiguration");
FirePropertyChanged("DisplayID");
}
}
public class LaneConfiguration : PolygonConfiguration
{
public override string DisplayID
{
get
{
return IsLaneGroup?string.Format("Lanes {0} - {1}", ID, ID + LaneCount - 1): string.Format("Lane {0}", ID);
}
}
}
I created a shorter example of this and reposted and got an answer.
I thought I only needed INotifyPropertyChanged on the code-behind. I actually needed it in my data object LaneConfiguration class as well. I should have paid closer attention to Ali Adl's comment. It would have saved me a day of frustration..
Thanks Ali Adl and Tim for your helpful answers !!
The right way is to make properties that you bindin-g - DependencyProperty - than you'll not have any problems with auto update.
If you use INotifyPropertyCahgnge than it must work, if it don't - check if PropertyChanged event == null.
I have a combobox and a listbox in a WPF window.
The combobox's itemssource is set to a List of all Team objects. Team has 2 properties (TeamId and TeamName).
The listbox's itemssource is set to a List of all Player objects. Player on of Players properties is TeamId.
I would like to filter the list of Players in the Listbox to only show those Players whose TeamId matches the TeamId of the SelectedItem in my combobox.
I would prefer to do this all in XAML but I'm not really sure on what the correct way to do it in C# would be either. Any help would be appreciated.
I'm not sure you can do it entirely in xaml, i think you might need a tiny bit of work somewhere else. This is how i did it for something else.
Wrap your collection with a CollectionViewSource in your xaml (this makes one that has a sort on a specific property name):
<CollectionViewSource x:Key="ViewName" Source="{Binding YourBinding}">
<CollectionViewSource.SortDescriptions>
<comp:SortDescription PropertyName="Name" Direction="Ascending" />
</CollectionViewSource.SortDescriptions>
</CollectionViewSource>
somewhere else, bind your listview to have this source as the itemssource:
<ListView x:Name="MyList" ItemsSource="{Binding Source={StaticResource ViewName}}" />
then somewhere in code, i have mine on a textbox property change listener, but you get the general idea. the ICollectionView interface has a filter member that you can use to filter things out.
private void TextBox_TextChanged(object sender, TextChangedEventArgs e)
{
var text = FilterTextBox.Text;
var source = MyList.Items as ICollectionView;
if (string.IsNullOrWhiteSpace(filter))
{
source.Filter = null;
}
else
{
source.Filter = delegate(object item)
{
var s = item as INamedItem;
return s.Name.IndexOf(filter, StringComparison.CurrentCultureIgnoreCase) != -1;
};
}
}
Firstly, change all your bound collections to ObservableCollection.
Then, on the combobox, bind the SelectedValue to another property on your DataContext of type Team (you have implemented INotifyPropertyChanged right?).
When the SelectedValue changes, refresh the ListBox's bound collection with a filtered list from the collection of all players:
public ObservableCollection<Team> Teams { get;set;}
public ObservableCollection<Player> Players { get;set;}
private List<Player> AllPlayers {get;set}
public Team CurrentTeam
{
get
{
return this._currentTeam;
}
set
{
this._currentTeam = value;
this.Players = new ObservableCollection(this.AllPlayers.Where(x => x.TeamId = this._currentTeam.TeamId));
RaisePropertyChanged("CurrentTeam");
}
}
This is the quickest and easist way to do it. You could probably achieve this through CollectionView, but I think this is simpler to understand.
I'm trying to do the following thing:
I have a TabControl with several tabs.
Each TabControlItem.Content points to PersonDetails which is a UserControl
Each BookDetails has a dependency property called IsEditMode
I want a control outside of the TabControl , named ToggleEditButton, to be updated whenever the selected tab changes.
I thought I could do this by changing the ToggleEditButton data context, by it doesn't seem to work (but I'm new to WPF so I might way off)
The code changing the data context:
private void tabControl1_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
if (e.Source is TabControl)
{
if (e.Source.Equals(tabControl1))
{
if (tabControl1.SelectedItem is CloseableTabItem)
{
var tabItem = tabControl1.SelectedItem as CloseableTabItem;
RibbonBook.DataContext = tabItem.Content as BookDetails;
ribbonBar.SelectedTabItem = RibbonBook;
}
}
}
}
The DependencyProperty under BookDetails:
public static readonly DependencyProperty IsEditModeProperty =
DependencyProperty.Register("IsEditMode", typeof (bool), typeof (BookDetails),
new PropertyMetadata(true));
public bool IsEditMode
{
get { return (bool)GetValue(IsEditModeProperty); }
set
{
SetValue(IsEditModeProperty, value);
SetValue(IsViewModeProperty, !value);
}
}
And the relevant XAML:
<odc:RibbonTabItem Title="Book" Name="RibbonBook">
<odc:RibbonGroup Title="Details" Image="img/books2.png" IsDialogLauncherVisible="False">
<odc:RibbonToggleButton Content="Edit"
Name="ToggleEditButton"
odc:RibbonBar.MinSize="Medium"
SmallImage="img/edit_16x16.png"
LargeImage="img/edit_32x32.png"
Click="Book_EditDetails"
IsChecked="{Binding Path=IsEditMode, Mode=TwoWay}"/>
...
There are two things I want to accomplish, Having the button reflect the IsEditMode for the visible tab, and have the button change the property value with no code behind (if posible)
Any help would be greatly appriciated.
You can accomplish what you want by binding directly to the TabControl's SelectedItem using the ElementName binding:
<odc:RibbonTabItem Title="Book" Name="RibbonBook">
<odc:RibbonGroup Title="Details" Image="img/books2.png" IsDialogLauncherVisible="False">
<odc:RibbonToggleButton Content="Edit"
Name="ToggleEditButton"
odc:RibbonBar.MinSize="Medium"
SmallImage="img/edit_16x16.png"
LargeImage="img/edit_32x32.png"
Click="Book_EditDetails"
IsChecked="{Binding ElementName=myTabControl, Path=SelectedItem.IsEditMode, Mode=TwoWay}"/>
Where myTabControl is the name of the TabControl (the value of the x:Name property). You shouldn't need to handle the SelectionChanged event anymore to update the DataContext of the button.
In WPF I have a collection of bool? values and I want to bind each of these to a separate checkbox programmatically. I want the bindings to be TwoWay so that changing the value of the individual item in the collection in code updates the check box and vice versa.
I have spent ages trying to figure out how to do this and I am completely stuck. With the following code the checkbox only gets the right value when the window is loaded and that's it. Changing the check box doesn't even update the value in the collection. (UPDATE: this appears to be a bug in .NET4 as the collection does get updated in an identical .NET3.5 project. UPDATE: Microsoft have confirmed the bug and that it will be fixed in the .NET4 release.)
Many thanks in advance for your help!
C#:
namespace MyNamespace
{
public partial class MyWindow : Window, INotifyPropertyChanged
{
public MyWindow()
{
InitializeComponent();
DataContext = this;
}
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
public List<bool?> myCollection = new List<bool?>
{ true, false, true, false, true, false };
public List<bool?> MyCollection
{
get { return myCollection; }
set { myCollection = value; }
}
}
}
XAML:
<CheckBox IsChecked="{Binding Path=MyCollection[0], Mode=TwoWay}">
There are a few things that need changing here to get this to work. Firstly you'll need to wrap your boolean value in an object that implements the INotifyPropertyChanged interface in order to get the change notification that you are looking for. Currently you are binding to boolean values in your collection which do not implement the interface. To do this you could create a wrapper class like so :
public class Wrapper: INotifyPropertyChanged
{
public event PropertyChangedEventHandler PropertyChanged;
protected void OnPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
private bool val = false;
public bool Val
{
get { return val; }
set
{
val = value;
this.OnPropertyChanged("Val");
}
}
public Wrapper(bool val)
{
this.val = val;
}
}
You'll then want to create these objects in your form instead of a list of booleans. You may also want to use an observable collection instead of a list so that notification of items being added and removed are sent. This is shown below:
public Window1()
{
InitializeComponent();
this.DataContext = this;
}
private ObservableCollection<Wrapper> myCollection = new ObservableCollection<Wrapper>()
{new Wrapper(true), new Wrapper(false), new Wrapper(true)};
public ObservableCollection<Wrapper> MyCollection
{
get { return myCollection; }
}
The next thing to do is to display a list of check boxes in your ui. To do this WPF provides itemscontrols. ListBox is an itemscontrol so we can use this as a starting point. Set the itemssource of a listbox to be MyCollection. We then need to define how each Wrapper object is going to be displayed in the list box and this can be done with a datatemplate which is created in the windows resources. This is shown below :
<Window.Resources>
<DataTemplate x:Key="myCollectionItems">
<CheckBox IsChecked="{Binding Path=Val, Mode=TwoWay}"></CheckBox>
</DataTemplate>
</Window.Resources>
<Grid>
<ListBox ItemsSource="{Binding Path=MyCollection}" ItemTemplate="{StaticResource myCollectionItems}"></ListBox>
</Grid>
This should get you up and running with a simple demo of checkboxes that have values bound to a list of booleans.
What makes you think it's not working? It's working for me :)
Here's my test XAML:
<UniformGrid>
<CheckBox IsChecked="{Binding Path=MyCollection[0], Mode=TwoWay}"/>
<ListBox ItemsSource="{Binding MyCollection}"/>
<Button Content="Test" Click="Button_Click"/>
</UniformGrid>
Here's my code behind:
private void Button_Click(object sender, RoutedEventArgs e)
{
}
(the rest is the same as yours)
I placed a breakpoint on Button_Click and checked MyCollection[0] it was updated according to the IsChecked value of the CheckBox.
Try changing your collection type from List<bool?> to ObservableCollection<bool?> perhaps that is the reason you think it's not working for you (the fact that changes to the collection are not reflected anywhere else in your view).
Change your List<bool?> to an ObservableCollection<bool?>. A List does not raise the change notifications that WPF needs to update the UI. An ObservableCollection does. This handles the case where the list entry is changed and the CheckBox needs to update accordingly.
In the other direction, it works for me even with a List<bool?> -- i.e. toggling the checkbox modifies the value in the collection. Your binding syntax is certainly correct.