TabControl: SelectedContent and SelectedItem return the same - wpf

Question

I'm displaying a list of custom objects (here: Customer) dynamicly, each in its own tab using TabControl, ItemsSource and DataTemplate:
MainWindows.xaml.cs:
using System.Collections.Generic;
using System.Diagnostics;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
namespace testTabControl
{
public class Customer
{
public string FirstName { get; set; }
public string LastName { get; set; }
public int NumberOfContracts { get; set; }
}
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
//create all
var customers = new List<Customer>
{
new Customer {FirstName = "Jim", LastName = "Smith", NumberOfContracts = 23},
new Customer {FirstName = "Jane", LastName = "Smiths", NumberOfContracts = 42},
new Customer {FirstName = "John", LastName = "Tester", NumberOfContracts = 32}
};
//show
myTabControl.ItemsSource = customers;
}
private void OnSizeChanged(object sender, SizeChangedEventArgs e)
{
Trace.WriteLine("myTabControl.SelectedContent is " + myTabControl.SelectedContent.GetType());
Trace.WriteLine("myTabControl.SelectedItem is " + myTabControl.SelectedItem.GetType());
// do something with content of the selected tab:
///myTabControl.SelectedContent.Foreground = new SolidColorBrush(Color.FromRgb(255, 0, 0));
}
}
}
MainWindow.xaml:
<Window x:Class="testTabControl.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:testTabControl="clr-namespace:testTabControl"
Title="MainWindow" Height="350" Width="525"
SizeChanged="OnSizeChanged"
>
<Window.Resources>
<DataTemplate x:Key="myContent" DataType="{x:Type testTabControl:Customer}">
<TextBlock x:Name="myContentRoot">
This is the content for
<TextBlock Text="{Binding FirstName}"/> <TextBlock Text="{Binding LastName}"/>
</TextBlock>
</DataTemplate>
<DataTemplate x:Key="myHeader" DataType="{x:Type testTabControl:Customer}">
<TextBlock Text="{Binding LastName}"/>
</DataTemplate>
</Window.Resources>
<TabControl
x:Name="myTabControl"
SelectedIndex="0"
ItemTemplate="{StaticResource ResourceKey=myHeader}"
ContentTemplate="{StaticResource ResourceKey=myContent}"
/>
</Window>
In the method OnSizeChanged I expected myTabControl.SelectedContent to return a TextBlock generated from DataTemplate. But an instance of Customer is returned! Same as by myTabControl.SelectedItem.
The only way I found to get the generated content is described here: http://msdn.microsoft.com/en-us/library/bb613579.aspx
Does anybody know any other solution without visual tree walk?

Answer 1

Your TabControl contains objects of type Customer. Templates can be used to tell WPF how to draw each Customer object, however it doesn't change the fact that the items in the TabControl are still Customer objects.
If you want to access a templated UI object for the item, you can either walk the VisualTree or use the ItemContainerGenerator to get the container holding the SelectedItem
For example,
var selectedItem = myTabControl.SelectedItem;
var selectedItemContainer =
myTabControl.ItemContainerGenerator.ContainerFromItem(selectedItem);

Answer 2

The reason your SelectedContent is returning a Customer object is this:
<DataTemplate x:Key="myContent" DataType="{x:Type testTabControl:Customer}">
It is returning exactly what you ask for. All the DataTemplate does is describe how to display the Customer object which is the content, nothing else. When you ask for content, it returns the object that the DataTemplate is displaying.
One way that you could do this house a property on your Customer object which replicates the output you want.
public string OutputString
{
get
{
return string.Format("This is the content for {0} {1}", this.FirstName, this.LastName);
}
}
And then do something like
Trace.WriteLine("myTabControl.SelectedContent is " + myTabControl.SelectedContent.OutputString);
Or you might could create a collection of strings that followed the format above, and make those the content. Then your SelectedContent would be a simple string by default.