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ļ»æ// Copyright Ā© Microsoft Corporation.
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// This source is subject to the Microsoft Source License for Silverlight Controls (March 2008 Release).
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// Please see http://go.microsoft.com/fwlink/?LinkID=111693 for details.
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// All other rights reserved.
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using System.ComponentModel;
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using System.Diagnostics;
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using System.Windows.Documents;
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using System.Windows.Markup;
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using System.Windows.Media;
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using System.Windows.Controls;
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namespace System.Windows.Controls
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/// Displays the content of a ContentControl.
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/// Typically, you the ContentPresenter directly within the ControlTemplate
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/// of a ContentControl to mark where the content should be displayed.
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/// Every type derived from ContentControl should have a ContentPrenter in
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/// its ControlTemplate (although it may not necessarily be a TemplatePart).
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/// The ContentPresenter in the ControlTemplate should use a TemplateBinding
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/// to associate ContentControl.Content with ContentPresenter.Content (and
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/// an other relevant properties like FontSize, VeriticalAlignment, etc.).
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public class ContentPresenter : Control
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/// XAML markup used to define the write-once ContentPresenter template.
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private const string ContentPresenterDefaultTemplate =
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"xmlns=\"http://schemas.microsoft.com/client/2007\" " +
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"xmlns:x=\"http://schemas.microsoft.com/winfx/2006/xaml\" " +
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"xmlns:controls=\"clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls\" " +
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"TargetType=\"controls:ContentPresenter\">" +
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"<Grid x:Name=\"RootElement\" " +
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"Background=\"{TemplateBinding Background}\" " +
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"Cursor=\"{TemplateBinding Cursor}\">" +
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"<TextBlock x:Name=\"TextElement\" " +
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"FontFamily=\"{TemplateBinding FontFamily}\" " +
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"FontSize=\"{TemplateBinding FontSize}\" " +
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"FontStretch=\"{TemplateBinding FontStretch}\" " +
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"FontStyle=\"{TemplateBinding FontStyle}\" " +
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"FontWeight=\"{TemplateBinding FontWeight}\" " +
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"Foreground=\"{TemplateBinding Foreground}\" " +
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"HorizontalAlignment=\"{TemplateBinding HorizontalContentAlignment}\" " +
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"Padding=\"{TemplateBinding Padding}\" " +
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"TextAlignment=\"{TemplateBinding TextAlignment}\" " +
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"TextDecorations=\"{TemplateBinding TextDecorations}\" " +
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"TextWrapping=\"{TemplateBinding TextWrapping}\" " +
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"VerticalAlignment=\"{TemplateBinding VerticalContentAlignment}\" " +
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"Visibility=\"Collapsed\" />" +
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/// Root element of the panel that will contain the visual content.
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/// Since a Control cannot change its content (i.e. it may only call
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/// InitializeFromXaml once to set its root), every ContentPresetner
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/// will create a container as its root element regardless of the
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/// content that will be stuffed into it. It's also worth noting that
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/// there is no TemplatePartAttribute because the Template is write-once
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/// and cannot be changed by users. This field is marked internal for
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internal Grid _elementRoot;
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internal const string RootElementName = "RootElement";
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/// Visual representation of the Content currently being displayed.
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/// <remarks>This field is marked internal for unit testing.</remarks>
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internal UIElement _elementContent;
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/// Visual representation of any text Content currently being displayed.
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/// The _elementText property is necessary in addition to the
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/// _elementContent property because of all of all the font related
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/// properties whose values need to be propogated into it by the
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/// ContentPresenter. This field is marked internal for unit testing.
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internal TextBlock _elementText;
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internal const string ElementTextContentName = "TextElement";
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/// True if the template has already been applied, false otherwise.
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internal bool _alreadyAppliedTemplate;
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/// Gets or sets the data used to generate the contentPresenter elements of a
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/// ContentPresenter.
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public object Content
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get { return GetValue(ContentProperty); }
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set { SetValue(ContentProperty, value); }
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/// Identifies the Content dependency property.
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public static readonly DependencyProperty ContentProperty =
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DependencyProperty.Register(
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typeof(ContentPresenter),
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new PropertyMetadata(OnContentPropertyChanged));
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/// ContentProperty property changed handler.
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/// <param name="d">ContentPresenter that changed its Content.</param>
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/// <param name="e">DependencyPropertyChangedEventArgs.</param>
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private static void OnContentPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
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ContentPresenter source = d as ContentPresenter;
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Debug.Assert(source != null,
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"The source is not an instance of ContentPresenter!");
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// Use the Content as the DataContext to enable bindings in
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if (source.ContentTemplate != null)
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source.DataContext = e.NewValue;
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// Display the Content
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source.PrepareContentPresenter();
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#region ContentTemplate
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/// Gets or sets the data template used to display the content of the
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/// ContentPresenter.
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public DataTemplate ContentTemplate
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get { return GetValue(ContentTemplateProperty) as DataTemplate; }
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set { SetValue(ContentTemplateProperty, value); }
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/// Identifies the ContentTemplate dependency property.
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public static readonly DependencyProperty ContentTemplateProperty =
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DependencyProperty.Register(
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typeof(DataTemplate),
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typeof(ContentPresenter),
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new PropertyMetadata(OnContentTemplatePropertyChanged));
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/// ContentTemplateProperty property changed handler.
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/// <param name="d">ContentPresenter that changed its ContentTemplate.</param>
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/// <param name="e">DependencyPropertyChangedEventArgs.</param>
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private static void OnContentTemplatePropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
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ContentPresenter source = d as ContentPresenter;
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Debug.Assert(source != null,
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"The source is not an instance of ContentPresenter!");
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// Use the Content as the DataContext to enable bindings in
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// ContentTemplate or clear it if we removed our template (NOTE:
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// this should use ClearValue instead when it's available).
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source.DataContext = e.NewValue != null ? source.Content : null;
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// Display the Content
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source.PrepareContentPresenter();
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#endregion ContentTemplate
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#region TextAlignment
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/// Gets or sets a value that indicates the horizontal alignment of text
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public TextAlignment TextAlignment
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get { return (TextAlignment) GetValue(TextAlignmentProperty); }
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set { SetValue(TextAlignmentProperty, value); }
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/// Identifies the TextAlignment dependency property.
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public static readonly DependencyProperty TextAlignmentProperty =
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DependencyProperty.Register(
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typeof(TextAlignment),
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typeof(ContentPresenter),
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#endregion TextAlignment
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#region TextDecorations
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/// Gets or sets a TextDecorationCollection that contains the effects to
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/// apply to the Content text.
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[TypeConverter(typeof(TextDecorationCollectionConverter))]
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public TextDecorationCollection TextDecorations
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get { return GetValue(TextDecorationsProperty) as TextDecorationCollection; }
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set { SetValue(TextDecorationsProperty, value); }
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/// Identifies the TextDecorations dependency property.
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public static readonly DependencyProperty TextDecorationsProperty =
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DependencyProperty.Register(
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typeof(TextDecorationCollection),
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typeof(ContentPresenter),
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#endregion TextDecorations
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/// Gets or sets a value that indicates how the TextBlock should wrap
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public TextWrapping TextWrapping
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get { return (TextWrapping) GetValue(TextWrappingProperty); }
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set { SetValue(TextWrappingProperty, value); }
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/// Identifies the TextWrapping dependency property.
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public static readonly DependencyProperty TextWrappingProperty =
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DependencyProperty.Register(
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typeof(TextWrapping),
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typeof(ContentPresenter),
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#endregion TextWrapping
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/// Initializes a new instance of the ContentPresenter class.
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public ContentPresenter()
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// Apply the default Template to ContentPresenter.
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Template = XamlReader.Load(ContentPresenterDefaultTemplate) as ControlTemplate;
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Debug.Assert(_alreadyAppliedTemplate,
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"The write-once Template flag _alreadyAppliedTemplate was not set!");
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/// Apply the default Template to ContentPresenter. This is only
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/// allowed to happen one time.
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public override void OnApplyTemplate()
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// Ensure that the Template property is set/applied only once (from
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if (_alreadyAppliedTemplate)
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throw new InvalidOperationException(Resource.ContentPresenter_OnApplyTemplate_WriteOnce);
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_alreadyAppliedTemplate = true;
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// Get the content root and the text content visual
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_elementRoot = GetTemplateChild(RootElementName) as Grid;
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Debug.Assert(_elementRoot != null,
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"The required template part RootElement was not found!");
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_elementText = GetTemplateChild(ElementTextContentName) as TextBlock;
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Debug.Assert(_elementText != null,
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"The required template part TextElement is not an instance of TextBlock!");
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// Ensure the template parts were structured correctly
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Debug.Assert(_elementContent == null,
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"_elementContent should not exist when applying the template!");
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Debug.Assert(_elementRoot.Children.Contains(_elementText),
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"TextElement should be a child of RootElement!");
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Debug.Assert(_elementRoot.Children.Count == 1,
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"RootElement should have TextElement as its only child!");
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/// Update the ContentPresenter's logical tree with the appropriate
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/// visual elements when its Content is changed.
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private void PrepareContentPresenter()
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Debug.Assert(_elementRoot != null, "RootElement is null!");
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Debug.Assert(_elementText != null, "TextElement is null!");
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// Remove the old content
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if (_elementContent != _elementText)
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_elementRoot.Children.Remove(_elementContent);
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_elementContent = null;
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_elementText.Text = null;
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// Expand the ContentTemplate if it exists
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DataTemplate template = ContentTemplate;
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object content = (template != null) ?
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template.LoadContent() :
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// Add the new content
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UIElement element = content as UIElement;
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_elementContent = element;
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_elementRoot.Children.Add(_elementContent);
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_elementText.Visibility = Visibility.Collapsed;
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else if (content != null)
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_elementText.Visibility = Visibility.Visible;
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_elementText.Text = content.ToString();
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_elementText.Visibility = Visibility.Collapsed;
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/// Returns the specified contentPresenter element.
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/// <param name="index">The index of the desired contentPresenter.</param>
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/// <returns>The contentPresenter element at the specified index value.</returns>
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protected virtual DependencyObject GetVisualChild(int index)
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throw new ArgumentOutOfRangeException("index");
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object content = Content;
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return (content == null) ?
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((content is UIElement) ?
added
removed
class/Microsoft.SilverlightControls/Controls/Src/ContentControl/ContentPresenter.cs
