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Andy De George
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title: "ScrollViewer Overview"
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description: Learn about the ScrollViewer control, which enables scrolling of content in Windows Presentation Foundation applications. See usage examples.
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ms.date: "03/30/2017"
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dev_langs:
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- "csharp"
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- "vb"
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- "cpp"
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helpviewer_keywords:
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- "controls [WPF], ScrollViewer"
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- "ScrollViewer control [WPF], about ScrollViewer control"
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ms.assetid: 94a13b94-cfdf-4b12-a1aa-90cb50c6e9b9
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---
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# ScrollViewer Overview
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Content within a user interface is often larger than a computer screen's display area. The <xref:System.Windows.Controls.ScrollViewer> control provides a convenient way to enable scrolling of content in [!INCLUDE[TLA#tla_winclient](../../../includes/tlasharptla-winclient-md.md)] applications. This topic introduces the <xref:System.Windows.Controls.ScrollViewer> element and provides several usage examples.
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<a name="what_is_a_scrollviewer_element"></a>
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## The ScrollViewer Control
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There are two predefined elements that enable scrolling in [!INCLUDE[TLA2#tla_winclient](../../../includes/tla2sharptla-winclient-md.md)] applications: <xref:System.Windows.Controls.Primitives.ScrollBar> and <xref:System.Windows.Controls.ScrollViewer>. The <xref:System.Windows.Controls.ScrollViewer> control encapsulates horizontal and vertical <xref:System.Windows.Controls.Primitives.ScrollBar> elements and a content container (such as a <xref:System.Windows.Controls.Panel> element) in order to display other visible elements in a scrollable area. You must build a custom object in order to use the <xref:System.Windows.Controls.Primitives.ScrollBar> element for content scrolling. However, you can use the <xref:System.Windows.Controls.ScrollViewer> element by itself because it is a composite control that encapsulates <xref:System.Windows.Controls.Primitives.ScrollBar> functionality.
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The <xref:System.Windows.Controls.ScrollViewer> control responds to both mouse and keyboard commands, and defines numerous methods with which to scroll content by predetermined increments. You can use the <xref:System.Windows.Controls.ScrollViewer.ScrollChanged> event to detect a change in a <xref:System.Windows.Controls.ScrollViewer> state.
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A <xref:System.Windows.Controls.ScrollViewer> can only have one child, typically a <xref:System.Windows.Controls.Panel> element that can host a <xref:System.Windows.Controls.Panel.Children%2A> collection of elements. The <xref:System.Windows.Controls.ContentPresenter.Content%2A> property defines the sole child of the <xref:System.Windows.Controls.ScrollViewer>.
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<a name="scrollviewer_physical_vs_logical"></a>
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## Physical vs. Logical Scrolling
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Physical scrolling is used to scroll content by a predetermined physical increment, typically by a value that is declared in pixels. Logical scrolling is used to scroll to the next item in the logical tree. Physical scrolling is the default scroll behavior for most <xref:System.Windows.Controls.Panel> elements. [!INCLUDE[TLA2#tla_winclient](../../../includes/tla2sharptla-winclient-md.md)] supports both types of scrolling.
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#### The IScrollInfo Interface
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The <xref:System.Windows.Controls.Primitives.IScrollInfo> interface represents the main scrolling region within a <xref:System.Windows.Controls.ScrollViewer> or derived control. The interface defines scrolling properties and methods that can be implemented by <xref:System.Windows.Controls.Panel> elements that require scrolling by logical unit, rather than by a physical increment. Casting an instance of <xref:System.Windows.Controls.Primitives.IScrollInfo> to a derived <xref:System.Windows.Controls.Panel> and then using its scrolling methods provides a useful way to scroll to the next logical unit in a child collection, rather than by pixel increment. By default, the <xref:System.Windows.Controls.ScrollViewer> control supports scrolling by physical units.
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<xref:System.Windows.Controls.StackPanel> and <xref:System.Windows.Controls.VirtualizingStackPanel> both implement <xref:System.Windows.Controls.Primitives.IScrollInfo> and natively support logical scrolling. For layout controls that natively support logical scrolling, you can still achieve physical scrolling by wrapping the host <xref:System.Windows.Controls.Panel> element in a <xref:System.Windows.Controls.ScrollViewer> and setting the <xref:System.Windows.Controls.ScrollViewer.CanContentScroll%2A> property to `false`.
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The following code example demonstrates how to cast an instance of <xref:System.Windows.Controls.Primitives.IScrollInfo> to a <xref:System.Windows.Controls.StackPanel> and use content scrolling methods (<xref:System.Windows.Controls.Primitives.IScrollInfo.LineUp%2A> and <xref:System.Windows.Controls.Primitives.IScrollInfo.LineDown%2A>) defined by the interface.
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[!code-csharp[IScrollInfoMethods#3](~/samples/snippets/csharp/VS_Snippets_Wpf/IScrollInfoMethods/CSharp/Window1.xaml.cs#3)]
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[!code-vb[IScrollInfoMethods#3](~/samples/snippets/visualbasic/VS_Snippets_Wpf/IScrollInfoMethods/VisualBasic/Window1.xaml.vb#3)]
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<a name="scrollviewer_markup_syntax_and_sample"></a>
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## Defining and Using a ScrollViewer Element
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The following example creates a <xref:System.Windows.Controls.ScrollViewer> in a window that contains some text and a rectangle. <xref:System.Windows.Controls.Primitives.ScrollBar> elements appear only when they are necessary. When you resize the window, the <xref:System.Windows.Controls.Primitives.ScrollBar> elements appear and disappear, due to updated values of the <xref:System.Windows.Controls.ScrollViewer.ComputedHorizontalScrollBarVisibility%2A> and <xref:System.Windows.Controls.ScrollViewer.ComputedVerticalScrollBarVisibility%2A> properties.
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[!code-cpp[ScrollViewer#1](~/samples/snippets/cpp/VS_Snippets_Wpf/ScrollViewer/CPP/ScrollViewer_wcp.cpp#1)]
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[!code-csharp[ScrollViewer#1](~/samples/snippets/csharp/VS_Snippets_Wpf/ScrollViewer/CSharp/ScrollViewer_wcp.cs#1)]
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[!code-vb[ScrollViewer#1](~/samples/snippets/visualbasic/VS_Snippets_Wpf/ScrollViewer/VisualBasic/ScrollViewer.vb#1)]
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[!code-xaml[ScrollViewer#1](~/samples/snippets/xaml/VS_Snippets_Wpf/ScrollViewer/XAML/Pane1.xaml#1)]
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<a name="scrollviewer_styling_scrollviewer"></a>
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## Styling a ScrollViewer
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Like all controls in Windows Presentation Foundation, the <xref:System.Windows.Controls.ScrollViewer> can be styled in order to change the default rendering behavior of the control. For additional information on control styling, see [Styling and Templating](/dotnet/desktop-wpf/fundamentals/styles-templates-overview).
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<a name="scrollviewer_scroll_vs_paginate"></a>
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## Paginating Documents
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For document content, an alternative to scrolling is to choose a document container that supports pagination. <xref:System.Windows.Documents.FlowDocument> is for documents that are designed to be hosted within a viewing control, such as <xref:System.Windows.Controls.FlowDocumentPageViewer>, that supports paginating content across multiple pages, preventing the need for scrolling. <xref:System.Windows.Controls.DocumentViewer> provides a solution for viewing <xref:System.Windows.Documents.FixedDocument> content, which uses traditional scrolling to display content outside the realm of the display area.
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For additional information about document formats and presentation options, see [Documents in WPF](../advanced/documents-in-wpf.md).
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## See also
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- <xref:System.Windows.Controls.ScrollViewer>
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- <xref:System.Windows.Controls.Primitives.ScrollBar>
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- <xref:System.Windows.Controls.Primitives.IScrollInfo>
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- [How to: Create a Scroll Viewer](https://docs.microsoft.com/previous-versions/dotnet/netframework-3.5/ms752352(v=vs.90))
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- [Documents in WPF](../advanced/documents-in-wpf.md)
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- [ScrollBar Styles and Templates](scrollbar-styles-and-templates.md)
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- [Controls](../advanced/optimizing-performance-controls.md)
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