Develop Reference

How do I retrieve the controls created by a DataTemplate?

I have a list of objects that I need to represent as a list of buttons.
These buttons should normally act as a regular Button; when the checkbox is checked, they should work as ToggleButtons and remain pressed. But I also need them to be mutually exclusive, like a RadioButton (only one can only be toggled at any time).
I tried using a RadioButton as the template for my ItemsControl, but they are not mutually exclusive (I guess that they are not actually children of the same control).
So I thought to use a ToggleButton as the template, manually uncheck it if the checkbox is not checked, and manually handle the mutual exclusion.
However, I can't find a way to retrieve the toggle buttons for the other items in the list to uncheck them.
Here's my XAML:
<Window x:Class="WpfApp9.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
Title="MainWindow" Height="450" Width="800">
<UniformGrid Rows="1">
<UniformGrid.Resources>
<DataTemplate x:Key="template">
<ToggleButton Name="Toggle"
Checked="ToggleButton_Checked"
Content="{Binding}"/>
</DataTemplate>
</UniformGrid.Resources>
<ItemsControl Name="lst" ItemTemplate="{StaticResource template}" />
<CheckBox Name="CheckToggle"
HorizontalAlignment="Center"
VerticalAlignment="Center">
TOGGLE
</CheckBox>
</UniformGrid>
</Window>
And this is my code-behind:
using System.Windows;
using System.Windows.Controls.Primitives;
namespace WpfApp9
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
lst.ItemsSource = new[] { "foo", "bar", "baz" };
}
private void ToggleButton_Checked(object sender, RoutedEventArgs e)
{
var toggle = (ToggleButton)sender;
// If the checkbox is not checked, release the button immediately
if (CheckToggle.IsChecked != true)
toggle.IsChecked = false;
// now how do I uncheck the other ToggleButtons?
}
}
}

I ended up solving the problem above in a different way.
In the question I said that
I tried using a RadioButton as the template for my ItemsControl, but they are not mutually exclusive (I guess that they are not actually children of the same control)
but I didn't realize I could use the GroupName property to force them into the same group. At this point the template can be this:
<DataTemplate x:Key="template">
<RadioButton Checked="RadioButton_Checked"
GroupName="SomeGroupName"
Content="{Binding}"/>
</DataTemplate>
And I get my mutually exclusive buttons without handling them manually.

Copy String of a ListViewItem into a TextBox

So I'm working on a calculator, basically a copy of the Windows Version, as a training excercise. I have implemented a History of past calculations, and I was asked to transform this history from TextBox to Listview.
What I want to do is copy one of the past calculations back into the Calculator TextBox when I click on it, just like in the Windows Calculator.
My ListViewCode:
<ListView Grid.Column="0" Grid.Row="1" Foreground="#616161" Name="history" Background="Transparent"
HorizontalAlignment="Stretch" BorderThickness="0" Margin="10,10,10,0">
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<EventSetter Event="MouseLeftButtonDown" Handler="RetrievePastCalculation" />
</Style>
</ListView.ItemContainerStyle>
</ListView>
And this is the RetrievePastCalculation method, but it doesn't work, nothing happens when I click on a ListViewItem. I'm new to WPF by the way.
private void RetrievePastCalculation(object sender, MouseButtonEventArgs e)
{
innerTextBox.Text = history.SelectedItems.ToString();
}
This is where I add items to the ListView I think, it's the Equal button method:
private void ButtonEquals_Click(object sender, RoutedEventArgs e)
{
Calculator calculate = new Calculator();
textBox.Text = calculate.Calculate(innerTextBox.Text);
history.Items.Add(innerTextBox.Text + "=" + textBox.Text);
innerTextBox.Clear();
}

history.SelectedItems is a collection, so calling ToString on it won't give you anything other than the name of the type. If you try it in the debugger (which you should), you'll see that it returns System.Windows.Controls.SelectedItemCollection. Now, at this point you can either fix your issue one of two ways: you can continue to use your current event-based approach, or you can use binding.
Events
With events, you can hook a handler to the Selected event for each ListItem that you add to the list:
private void ButtonEquals_Click(object sender, RoutedEventArgs e)
{
Calculator calculate = new Calculator();
textBox.Text = calculate.Calculate(innerTextBox.Text);
var item = new ListViewItem();
item.Content = innerTextBox.Text + "=" + textBox.Text;
item.Selected += HistoryItem_Selected //hooks the handler to the 'Selected' event
history.Items.Add(item);
innerTextBox.Clear();
}
then define the handler itself:
private void HistoryItem_Selected(object sender, RoutedEventArgs e)
{
// here 'sender' will be the ListItem which you clicked on
// but since it's an object we need to cast it first
ListViewItem listItem = (ListViewItem)sender;
// now all that's left is getting the text and assigning it to the textbox
innerTextBox.Text = listItem.Content.ToString();
}
Binding
Binding is much simpler as far as the amount of code is concerned, but has a steeper learning curve. Here, instead of setting the TextBox.Text property directly, we will specify a binding expression. This means that the value will always be the same as that of the bound expression.
<Window x:Class="WpfApplication1.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Grid>
<StackPanel>
<ListView Grid.Column="0" Grid.Row="0" Name="history" />
<TextBox Text="{Binding ElementName=history, Path=SelectedItem.Content}" />
<Button Name="ButtonEquals" Content="equals" Click="ButtonEquals_Click"/>
</StackPanel>
</Grid>
</Window>
I've run this in a new WPF project and it works as expected: the text box displays whatever text is in the clicked item from the list.
One thing to note is that both solutions assume that you are assigning strings to the ListViewItem Content. As you may know, you can assign other controls or any object to the Content property of a UI Control (ListViewItem inherits from Control). That's why the ListViewItem.Add method takes an argument of type object and is not restricted to one of type string. If you assigned anything other than a string in your button click event handler, both of the two cases above would likely break.

You could bind the value of the TextBox to the SelectedItem of the ListView. Here's an example:
<Page
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<StackPanel>
<ListView Grid.Column="0" Grid.Row="0" Foreground="#616161" Name="history" Background="Transparent"
HorizontalAlignment="Stretch" BorderThickness="0" Margin="10,10,10,0">
<ListViewItem>Calc1</ListViewItem>
<ListViewItem>Calc2</ListViewItem>
</ListView>
<TextBox Text="{Binding ElementName=history, Path=SelectedItem.Content}" />
</StackPanel>
</Page>

<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="100"/>
<RowDefinition Height="100"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<ListView Grid.Column="0" Grid.Row="0" Foreground="#616161" Name="history" BorderThickness="1,1" Height="50" Width="200" SelectionChanged="history_SelectionChanged">
<ListViewItem>
<TextBlock> A ListView</TextBlock>
</ListViewItem>
<ListViewItem>
with several
</ListViewItem>
<ListViewItem>
items
</ListViewItem>
</ListView>
<TextBox Grid.Row="1" Text="{Binding ElementName=history,Path=SelectedValue.Content}"
BorderThickness="1,1" Height="50" Width="200" />
</Grid>
It's better if you do it using XAML code. try to select item 0 and 1 to see the difference and understand how listboxworks.
now replace the text of textbox binding with following:
Text="{Binding ElementName=history,Path=SelectedValue.Content.Text}"
and seee the output for item 0. Hopefully you'll achieve desired output with a lot less effort.
Now that you have explained the whole problem i think you need to implement a converter in the text binding of TextBox. like below text
Text="{Binding ElementName=history,Path=SelectedValue.Content.Text,Converter={StaticResource mytextconverter}}"
and write down a logic to extract a part of text on the basis of '=' char. It's very easy to write a converter class. to write a converter follow the below link:
WPF Converter example

ListView Grid Item Holding not working

I'm using a ListView with more than one DataTemplate. I'm trying to detect when the user clicks on an Item to show a Flyout.
GridItem_Holding is never called.
XAML:
<DataTemplate x:Key="myKey1">
<Grid Holding="GridItem_Holding">
...
</Grid>
</DataTemplate>
<DataTemplate x:Key="myKey2">
<Grid Holding="GridItem_Holding">
...
</Grid>
</DataTemplate>
Code behind:
private void GridItem_Holding(object sender, HoldingRoutedEventArgs e)
{
}

Try like this
<Grid x:Name="GridListItem" Holding="Grid_Holding">

Have you remembered IsHoldingEnabled on Grid or children? Holding event is not triggered unless it is set true.

ListView ObservableCollection binding

I'm having problem with binding Collection do ListView.
public static ObservableCollection<ParagonViewClass> mparagonViewList = new ObservableCollection<ParagonViewClass>();
public ObservableCollection<ParagonViewClass> paragonViewList
{
get
{
return mparagonViewList;
}
}
In method, when user add new item, I'm adding it to list:
paragonViewList.Insert(0, newPar);
Also tried with mparagonViewList.Insert(0, newPar);
Itemssource in xaml file:
<ListView Grid.Row="1" Name="paragonListView1" ItemsSource="{Binding paragonViewList}" .../>
#EDIT: Listview have DataTemplate (Grid with labels - im prettu sure that binding is ok, becouse it works with just simply setting myListVIew.ItemsSource = myLis;)
It looks like when I click on product to add to listview it does insert to database, but I cannot see that product on listview. Probably there's little stupid problem, but I cant really find it ;)
Thanks for any answers!

Looking at the code you supplied, it is hard to figure out what you are doing wrong, if anything. So, I have thrown together a little sample application that works (from the WPF point of view anyway).
My model is called ItemModel, rather than ParagonViewClass, and is defined as follows
public class ItemModel
{
public ItemModel() { }
public string Text { get; set; }
}
My Xaml is
<Window x:Class="StackOverflow._20799346.MainWindow" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:common="clr-namespace:StackOverflow.Common;assembly=StackOverflow.Common"
DataContext="{Binding RelativeSource={RelativeSource Self}}"
Title="MainWindow" Height="350" Width="525">
<DockPanel>
<StackPanel Orientation="Horizontal" DockPanel.Dock="Top">
<Button Content="Add Item" Click="AddItem_OnClick" />
</StackPanel>
<ListView ItemsSource="{Binding Path=Items}">
<ListView.ItemTemplate>
<DataTemplate DataType="{x:Type common:ItemModel}">
<TextBlock Text="{Binding Path=Text}" />
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</DockPanel>
</Window>
Note the DataContext being bound to RelativeSource Self, allowing the code behind to be used as the ViewModel. I usually prefer to create a separate ViewModel class but this approach has its advantages as one can event directly from a control into the ViewModel, rather than mucking around with commands.
The code behind, now the view model, looks like
public partial class MainWindow : Window
{
private ObservableCollection<ItemModel> items;
public MainWindow()
{
InitializeComponent();
}
public ObservableCollection<ItemModel> Items { get { return items ?? (items = new ObservableCollection<ItemModel>()); } }
private void AddItem_OnClick(object sender, RoutedEventArgs e)
{
Items.Add(new ItemModel() { Text = Items.Count.ToString(CultureInfo.CurrentCulture) });
}
}
I have utilised a lazy load technique on the Items property. It will only be instantiated when it is accessed. For simplicity, when the Add Item button is clicked, I am adding a new item with its text set to the count of the Items collection.
You should be able to past this code into a new WPF application project, fix the namespacing in the xaml file and run it.
Now, as hinted at above by Rohit Vats, the Items property does not require a Setter. The ObservableCollection itself notifies the WPF binding subsystem when an item has been added or removed via both the INotifyPropertyChanged and INotifyCollectionChanged interfaces, both of which it implements.
I know this does not directly answer your question but with out further information (ie code) about the original problem, it is not possible to know what is going wrong.
Hopefully the example helps.
NOTE: I have removed exception management for brevity.

Bind a collection to a WPF ListBox

Update: I've updated the code based on your help so far, and still no luck. When the application loads the ListBox has no items. I assign junk values to Customers in the windows's contructor, and then am also trying to set the ListBox's DataContext as follows:
CustomerList.DataContext = Customers;
--- Original Question (with updated code) ---
I'm having trouble with databinding in a WPF project.
I have a class, Customer, as follows:
public class Customer
{
public String Name { get; set; }
public String Email { get; set; }
}
In my XAML's code behind I have a collection of customers as follows:
public List<Customer> Customers { get; set; }
I'm trying to bind each customer to a ListBox with a ListItemTemplate displaying the customer's information (name/email) in TextBoxes along with a button which locks/unloacks the TextBoxes (sets the IsEnabled property to true or false).
What's the best way to go about this?
So far I've been tryingt he following with no success.
In the XAML I currently have the following (ignoring the toggle part for now, I'm just trying to get the collection itself to be listed.):
<Window.Resources>
<CollectionViewSource x:Key="Customers" Source="{Binding Path=Customers, Mode=TwoWay}"/>
<DataTemplate x:Key="Customer">
<StackPanel Orientation="Horizontal">
<TextBox Content="{Binding Name}" />
<TextBox Content="{Binding Email}" />
</StackPanel>
</DataTemplate>
</Window.Resources>
<StackPanel>
<ListBox ItemsSource="{Binding Source={StaticResource Customers}}"
ItemTemplate="{StaticResource ResourceKey=Customer}"
Name="CustomerList"
Height="300" />
</StackPanel>

You need to change
ItemsSource="{Binding Source=Customers}"
to
ItemsSource="{Binding Source={StaticResource Customers}}" DataContext="{StaticResource Customers}"

Code similar to the updated one works for me after changing
<TextBox Content="{Binding Name}" />
to
<TextBox Text="{Binding Name}" />
As TextBox doesn't have Content property(like a Label), the former refused to compile in VS.
Well, it is set to Text in definition:
[ContentPropertyAttribute("Text")]
public class TextBox : TextBoxBase, IAddChild
But I thought it is only used between the brackets(<TextBox>Like so</TextBox>)?
Could this be the source of the problem?

Try setting the ItemsSource of your CustomerList as follows: ItemsSource="{Binding}". You've set the DataContext of the ListBox to the list of customers, you need to set the ItemsSource to the same collection, hence, the direct binding.
Another thing that you can do, in case you prefer to use the CollectionViewSource, is to set the DataContext of your window to the same class DataContext=this, because without this, the resource definition won't be able to locate the "Customers" collection that you defined in the code behind. If you do this, however, you don't need CustomerList.DataContext = Customers; because you're directly assigning the ItemsSource to a static resource, not relatively to the DataContext.
One more thing. I think you should give the CollectionViewSource and the corresponding collection in the code behind different names. This isn't going to cause a runtime issue, but it makes it hard to maintain the code ;)
Hope this helps :)