Assembly: PresentationFramework (in PresentationFramework.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
The value for a ScrollBar control is equivalent to the size of the scrollable content minus the size of the visible content area or viewport. For example, if the size of the content is 100 and the size of the ViewportSize property is 30, the value of the property is 70. This is true because the Value property of the ScrollBar control corresponds to the position in the scrollable content that appears at the top of the viewport. When the content is scrolled to the very bottom in this example, 30 percent of the content still appears in the viewport. Therefore, the Value that corresponds to the top of the viewport is 70, and the value is 70.