ScrollBar.ViewportSize Property


The .NET API Reference documentation has a new home. Visit the .NET API Browser on to see the new experience.

Gets or sets the amount of the scrollable content that is currently visible.

Namespace:   System.Windows.Controls.Primitives
Assembly:  PresentationFramework (in PresentationFramework.dll)

member ViewportSize : float with get, set

Property Value

Type: System.Double

The amount of the scrollable content that is currently visible. The default is 0.

The units that are used for ViewportSize are the same units that are used to describe the length of the content. Some examples include lines of text or pages of text.

The value of the ViewportSize property is used to calculate the size of the Thumb control that is displayed as the sliding value indicator in a ScrollBar control. The Thumb control's size represents the amount of a ScrollViewer control's content that is visible. If 25 percent of a ScrollViewer control's content is visible, the Thumb occupies 25 percent of the track in the ScrollBar.

You can decide which units ViewportSize uses. When you set this property, make sure that the ViewportSize, Minimum, Maximum, and Value properties use the same units.

The following illustration shows how the Thumb size reflects the amount of content that is visible.

The track length and thumbsize of a ScrollBar

Identifier field


Metadata properties set to true


The following example shows how to set the ViewportSize on a ScrollBar control.

No code example is currently available or this language may not be supported.
<ScrollBar Name="myScrollBarViewport" Orientation="Horizontal" ViewportSize="10"/>

.NET Framework
Available since 3.0
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Return to top