Use Linq to get control from a container : UI Element « Windows Presentation Foundation « VB.Net Tutorial

1. VB.Net Tutorial
2. Windows Presentation Foundation
3. UI Element

<Window x:Class="WpfApplication1.Window1"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Title="WPF" SizeToContent="Height" Width="300">
    <Grid Name="grid">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition/>
            <ColumnDefinition/>
        </Grid.ColumnDefinitions>
        <Border Grid.Column="0" BorderBrush="Gray" BorderThickness="1" />
        <Border Grid.Column="1" BorderBrush="Gray" BorderThickness="1" />
        <StackPanel Grid.Column="0" HorizontalAlignment="Center" Margin="5" Name="spLeftContainer">
            <TextBlock FontSize="16" Text="Radio Group 1" />
            <RadioButton Content="Radio Button 1A" GroupName="Group1" IsChecked="True" Margin="5" Name="rbnOneA" />
            <RadioButton Content="Radio Button 1B" GroupName="Group1" Margin="5" Name="rbnOneB" />
            <RadioButton Content="Radio Button 1C" GroupName="Group1" Margin="5" Name="rbnOneC" />
            <Separator/>
            <TextBlock FontSize="16" Text="Radio Group 2" />
            <RadioButton Checked="RadioButton_Checked" GroupName="Group2" Content="Radio Button 2A" IsChecked="True" 
                         Margin="5" Name="rbnTwoA" />
            <RadioButton Checked="RadioButton_Checked" GroupName="Group2" Content="Radio Button 2B" Margin="5" Name="rbnTwoB"/>
            <RadioButton Checked="RadioButton_Checked" GroupName="Group2" Content="Radio Button 2C" Margin="5" Name="rbnTwoC"/>
        </StackPanel>
        <StackPanel Grid.Column="1" HorizontalAlignment="Center" Margin="5" Name="spRightContainer">
            <TextBlock FontSize="16" Text="Radio Group 1" />
            <RadioButton Content="Radio Button 1D" GroupName="Group1" Margin="5" Name="rbnOneD" />
            <RadioButton Content="Radio Button 1E" GroupName="Group1" Margin="5" Name="rbnOneE" />
        </StackPanel>
        <Button Content="Show Group1 Selection" Grid.ColumnSpan="2" Grid.Row="1" HorizontalAlignment="Center" 
                Margin="10" MaxHeight="25" Click="Button_Click" />
    </Grid>
</Window>

//File:Window.xaml.vb
Imports System
Imports System.Linq
Imports System.Windows
Imports System.Windows.Controls

Namespace WpfApplication1
  Public Partial Class Window1
    Inherits Window
    Public Sub New()
      InitializeComponent()
    End Sub
    Private Sub Button_Click(sender As Object, e As RoutedEventArgs)
      Dim radioButton As RadioButton = Nothing
      radioButton = GetCheckedRadioButton(spLeftContainer.Children, "Group1")
      If radioButton Is Nothing Then
        radioButton = GetCheckedRadioButton(spRightContainer.Children, "Group1")
      End If
      MessageBox.Show(Convert.ToString(radioButton.Content) & " checked.", Title)
    End Sub
    Private Function GetCheckedRadioButton(children As UIElementCollection, groupName As [String]) As RadioButton
      Return children.OfType(Of RadioButton)().FirstOrDefault(Function(rb) rb.IsChecked = True AndAlso rb.GroupName = groupName)
    End Function
    Private Sub RadioButton_Checked(sender As Object, e As RoutedEventArgs)
      If Not Me.IsInitialized Then
        Return
      End If
      Dim radioButton As RadioButton = TryCast(e.OriginalSource, RadioButton)

      If radioButton IsNot Nothing Then
        MessageBox.Show(Convert.ToString(radioButton.Content) & " checked.", Title)
      End If
    End Sub
  End Class
End Namespace

16.50.UI Element
	16.50.1.	Find enclosure component
	16.50.2.	Clear locally set values and restore the default values of dependency properties
	16.50.3.	PresentationTraceSources.SetTraceLevel(binding,PresentationTraceLevel.High);
	16.50.4.	UI Element Mouse Clicked Events
	16.50.5.	Programmatically Extract an Element's Style with DefaultStyleKeyProperty
	16.50.6.	Print Logical Tree
	16.50.7.	Print Visual Tree
	16.50.8.	About Dialog with Tree Walking
	16.50.9.	Changing graphical elements
	16.50.10.	UIElement Count
	16.50.11.	Use Linq to get control from a container
	16.50.12.	Find inner visual element
	16.50.13.	Logical Visual Tree Sample
	16.50.14.	Point Hit Test with VisualTreeHelper.HitTest
	16.50.15.	Change the Visibility property of a UIElement.
	16.50.16.	Mixing graphics with Control Elements