Develop Reference

ContentControl and CollectionView.CurrentItem

Referencing this example:
https://learn.microsoft.com/en-us/dotnet/framework/wpf/data/how-to-bind-to-a-collection-and-display-information-based-on-selection
(some relevant code snippets:)
<Window.Resources>
<local:People x:Key="MyFriends"></local:People>
<DataTemplate x:Key="DetailTemplate">
<Border Width="300" Height="100" Margin="20"
BorderBrush="Aqua" BorderThickness="1" Padding="8">
<Grid>
<Grid.RowDefinitions>
<RowDefinition/>
<RowDefinition/>
<RowDefinition/>
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="First Name:"/>
<TextBlock Grid.Row="0" Grid.Column="1" Text="{Binding Path=FirstName}"/>
<TextBlock Grid.Row="1" Grid.Column="0" Text="Last Name:"/>
<TextBlock Grid.Row="1" Grid.Column="1" Text="{Binding Path=LastName}"/>
<TextBlock Grid.Row="2" Grid.Column="0" Text="Home Town:"/>
<TextBlock Grid.Row="2" Grid.Column="1" Text="{Binding Path=HomeTown}"/>
</Grid>
</Border>
</DataTemplate>
</Window.Resources>
<ListBox Width="200" IsSynchronizedWithCurrentItem="True"
ItemsSource="{Binding Source={StaticResource MyFriends}}"/>
<ContentControl x:Name="contentControl1"
Content="{Binding Source={StaticResource MyFriends}}"
ContentTemplate="{StaticResource DetailTemplate}" />
Both ListBox.ItemsSource and ContentControl.Content bind to the same source (MyFriends, an instance of the People class which derives from ObservableCollection<Person>). If my understanding is correct, this means that both the ListBox.ItemsSource and ContentControl.Content properties will be bound to the same implicitly created instance of ListCollectionView.
I understand that setting ListBox.IsSynchronizedWithCurrentItem="True" synchronizes ListBox.SelectedItem and ItemCollection.CurrentItem.
DetailTemplate (above) displays the details of the selected ListBox item, despite being 'bound' to a ListCollectionView. Specifying Path=/ (what I thought would be necessary to achieve the resulting behavior) does not have any effect - it's as if WPF knows to do it implicitly somehow:
<ContentControl x:Name="contentControl1"
Content="{Binding Source={StaticResource MyFriends}, Path=/}"
ContentTemplate="{StaticResource DetailTemplate}" />
As a test, I created another ContentControl with Content bound to a DataTemplate containing a ListBox:
<ContentControl x:Name="contentControl2"
Content="{Binding Source={StaticResource MyFriends}}"
ContentTemplate="{StaticResource DetailTemplate2}" />
<DataTemplate x:Key="DetailTemplate2">
<ListBox ItemsSource="{Binding}"></>
</DataTemplate>
And it displayed the list.
My question is: Why does DataTemplate get the selected Person object while the ListBox and DetailTemplate2 get the People collection?
(the behavior is desirable, I just don't understand what black magic is occurring under the hood to make it so)

Is a good question! I didn't notice that until read your post. So, after did some digging from source code of PropertyPathWorker, it appears that when PropertyPathWorker failed to solve a member of an object, in your case, it try to solve 'FirstName', 'LastName' ect. with 'MyFriends', it will try to solve it with the view of the object. And if still failed, it will try to solve it with view's CurrentItem, and that's where the magic happened. You can find those codes in PropertyPathWorker.UpdateSourceValueState(int k, ICollectionView collectionView, object newValue, bool isASubPropertyChange) and PropertyPathWorker.ReplaceItem(int k, object newO, object parent).

UWP Master/Detail view

I am searching for a good example how to build a master/detail view for UWP Win 10 app like shown on this page: https://msdn.microsoft.com/en-us/library/windows/apps/dn997765.aspx
For example Windows Mail app has the same master/detail view. How can I implement this style? On the left side I think to use a listview, but how to show the data in the Detail side? Can I use a Frame or ContentPresenter? How can enable/disable the detail view on phone/tablet/pc?
Hope there is example or tutorial which shows how to deal with this.

It's good to have some app architecture... The Windows XAML community already worked on it.
https://github.com/Windows-XAML/Template10/tree/master/Samples/MasterDetail

I think:
https://blogs.msdn.microsoft.com/johnshews_blog/2015/09/09/a-minimal-mvvm-uwp-app/
is a good exemple.
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto"/>
<ColumnDefinition Width="Auto"/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="0" Orientation="Vertical">
<ListView x:Name="MainList"
ItemsSource="{x:Bind Organization.People, Mode=OneWay}"
SelectedIndex="{x:Bind Organization.SelectedIndex, Mode=TwoWay}"
MinWidth="250" Margin="5">
<ListView.ItemTemplate>
<DataTemplate x:DataType="viewModels:PersonViewModel" >
<TextBlock Text="{x:Bind Name, Mode=OneWay}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackPanel>
<StackPanel Grid.Column="2" Orientation="Vertical">
<TextBox
Text="{x:Bind Organization.SelectedPerson.Name, Mode=TwoWay, FallbackValue=''}"
Margin="5" />
<TextBox
Text="{x:Bind Organization.SelectedPerson.Age, Mode=TwoWay, FallbackValue='0'}"
Margin="5" />
</StackPanel>
</Grid>
You can also find another exemple in samples app :https://github.com/Microsoft/Windows-universal-samples/tree/master/Samples/XamlListView

You can also use the MasterDetailsView Control provided by the UWP Community Toolkit.

You can use region frames. Here is an example for MvvmCross.
<SplitView x:Name="RootSplitView"
DisplayMode="Inline"
OpenPaneLength="256"
IsTabStop="False">
<SplitView.Pane>
<StackPanel Margin="0,50,0,0">
<Button Content="Second" Command="{x:Bind Vm.SecondCommand}" />
<Button Content="Third" Command="{x:Bind Vm.ThirdCommand}" />
</StackPanel>
</SplitView.Pane>
<!-- OnNavigatingToPage we synchronize the selected item in the nav menu with the current page.
OnNavigatedToPage we move keyboard focus to the first item on the page after it's loaded and update the Back button. -->
<Frame x:Name="FrameContent">
<Frame.ContentTransitions>
<TransitionCollection>
<NavigationThemeTransition>
<NavigationThemeTransition.DefaultNavigationTransitionInfo>
<EntranceNavigationTransitionInfo/>
</NavigationThemeTransition.DefaultNavigationTransitionInfo>
</NavigationThemeTransition>
</TransitionCollection>
</Frame.ContentTransitions>
</Frame>
</SplitView>
In the code behind file add
public Frame AppFrame { get { return (Frame)this.WrappedFrame.UnderlyingControl; } }
Add this in setup.cs file
protected override IMvxWindowsViewPresenter CreateViewPresenter(IMvxWindowsFrame rootFrame)
{
return new MvxWindowsMultiRegionViewPresenter(rootFrame);
}
for newer versions use:
protected override IMvxWindowsViewPresenter CreateViewPresenter(IMvxWindowsFrame rootFrame)
{
return new MvxWindowsMultiRegionViewPresenter(rootFrame);
}
Add following attribute at the top of the code behind file of child view:
[MvxRegion("FrameContent")]
For later versions:
[MvxRegionPresentation("FrameContent")]
Use this for navigating to child view:
ShowViewModel<SecondViewModel>()
Refer to this link: https://depblog.weblogs.us/2015/11/23/mvvmcross-uwp-splitview/
Examples: https://github.com/MvvmCross/MvvmCross-Samples/tree/master/XPlatformMenus

WPF Bind to object (non static) method

I'm trying to bind to an instance method of an object but I can only find examples to bind to properties or static methods. Here's the relevant part of my code:
<Window.Resources>
<ObjectDataProvider x:Key="identifier" MethodName="getIdentifier" ObjectType="{x:Type self:PartModel}" />
</Window.Resources>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid Margin="0,0,0,5">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="20" />
<ColumnDefinition Width="80"/>
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding identifier}" Grid.Column="0" />
<TextBlock Text="{Binding Title}" Grid.Column="1" />
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
PartModel is an object that I use for filling the ItemsControl. The Title shows up and the getIdentifier method works when I call it in my regular code. But in my View only the title shows and the column for the identifier remains empty.
Is this even possible or do I have to write the identifier to a property of the model?

You are currently binding to an identifier property, which does not exist on the DataContext object of your list items.
Set the binding Source object instead, to the ObjectDataProvider resource that is references by the identifier resource key:
<TextBlock Text="{Binding Source={StaticResource identifier}}"/>

ListBox ItemsSource Binding doesn't work

I'm developing a Windows Phome application. I have the following ListBox on a page:
<ListBox Margin="10,10,8,8" x:Name="WallList">
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel />
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<Grid x:Name="ListBoxItemLayout" Background="Transparent" Margin="10">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="0.33*"/>
<ColumnDefinition Width="0.77*"/>
</Grid.ColumnDefinitions>
<Image HorizontalAlignment="Left" Margin="0" Source="{Binding ImagePath}" Height="200"/>
<StackPanel Margin="5,0,0,0" Grid.Column="1">
<TextBlock x:Name="Name" TextWrapping="Wrap" Text="{Binding Name}" Style="{StaticResource PhoneTextTitle2Style}"/>
<TextBlock x:Name="Comment" Margin="0,5,0,0" TextWrapping="Wrap" Text="{Binding Comment}" Style="{StaticResource PhoneTextNormalStyle}" Height="130"/>
<TextBlock x:Name="When" TextWrapping="Wrap" Text="{Binding When}" Style="{StaticResource PhoneTextTitle3Style}" VerticalAlignment="Bottom"/>
</StackPanel>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
I'm using this to fill the ListBox on Loaded event:
this.WallList.ItemsSource = StartingWall.GetWallPosts();
And now I want to add more items programmatically when the user write down some text on a TextBox and click on a button. I want to place this text on Comment field.
I'm gooing to fill the rest fields with default data.
My question is:
How can I add more items to WallList ListBox?
Someone has suggested to do the following:
public ObservableCollection<WallPostEntry> MyWallPosts {get;set;}
// Initialize MyWallPosts to whatever
MyWallPosts.Add(new WallPostEntry("new entry"));
<ListBox Margin="10,10,8,8" x:Name="WallList" ItemsSource="{Binding MyWallPosts}">
But Binding ListBox ItemsSource doesn't work for me. I'm initializing MyWallPosts on constructor, just before InitializeComponent();, like this:
public Wall()
{
MyWallPosts = StartingWall.GetWallPosts();
InitializeComponent();
}
Any advice?
Thanks.

I see a couple wierd things:
first, you're using the itemssource binding in one place, but explicitly setting it in another? setting something in code will override/undo any bindings, so that could cause a problem (but it looks like you're setting it to the same thing so that shouldn't make a difference, but i'd remove the this.WallList.ItemsSource = StartingWall.GetWallPosts(); call entirely, and leave the ItemsSource="{Binding MyWallPosts}" in the xaml. the point of using bindings is to get rid of this kind of code)
second, you're setting mywallposts and using a binding, but not setting the datacontext on your object itself? simplest in your example would be to just add one line to your constructor:
public Wall()
{
DataContext = this;
MyWallPosts = StartingWall.GetWallPosts();
InitializeComponent();
}
My next suggestion would be to simplify until it works. leave the listbox but comment out all of the item/data templating to make sure that you don't have a bug in your template

Could he just add
a DataContext property to this:
<ListBox Margin="10,10,8,8" x:Name="WallList" ItemsSource="{Binding MyWallPosts}">
so:
<ListBox Margin="10,10,8,8" x:Name="WallList" ItemsSource="{Binding MyWallPosts}" DataContext="{Binding MyWallPosts}">
Would there be any way of setting the dataContext declarativelly?
tks,
Oscar

How to get checked items in a WPF ListBox?

I have a WPF ListBox where I have checkboxes, but what's the way to get the list of items that are checked?
The ListBox is data binded to a Dictionary<T>.
Here is the XAML:
<Window x:Class="WpfApplication.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1"
Height="300"
Width="300">
<Grid Margin="10">
<ListBox ItemsSource="{DynamicResource Nodes}" Grid.IsSharedSizeScope="True" x:Name="MyList">
<ListBox.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition SharedSizeGroup="Key" />
<ColumnDefinition SharedSizeGroup="Name" />
<ColumnDefinition SharedSizeGroup="Id" />
</Grid.ColumnDefinitions>
<CheckBox Name="NodeItem" Click="OnItemChecked">
<StackPanel Orientation="Horizontal">
<TextBlock Margin="2" Text="{Binding Value.Name}" Grid.Column="1"/>
<TextBlock Margin="2" Text="-" Grid.Column="2"/>
<TextBlock Margin="2" Text="{Binding Value.Id}" Grid.Column="3"/>
</StackPanel>
</CheckBox>
</Grid>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
</Window>

This is usually done through a ViewModel, that is a data structure that exposes to the view (through the DataContext) both the model (your data) and view-specific information, like whether an item is checked or not.
In your example, your Dictionary would not be, say, a Dictionary, but a Dictionary and the PersonViewModel would have a IsChecked property and a Person property pointing to the model.
Otherwise, you have to go and find the checkbox in templates or get to the list box item from the checkbox and this gets complex pretty fast.

Josh Smith has an article on codeproject that should explain what you need. He is discussing a TreeView but the principle will port over to the CheckBox as well.
There is also a very interesting approach here using a DataTemplate and Binding the CheckBox.IsChecked property to the ListBoxItem.IsSelected property.
If you are new to MVVM, Jason Dolinger has an excellent video on the subject. It steps you through the process moving from using code behind files to a full MVVM pattern including Dependency Injection and Testing.