I have a TextBlock in WPF. I write many lines to it, far exceeding its vertical height. I expected a vertical scroll bar to appear automatically when that happe
TextBlock
You can use
ScrollViewer.HorizontalScrollBarVisibility="Visible" ScrollViewer.VerticalScrollBarVisibility="Visible"
These are attached property of wpf. For more information
http://wpfbugs.blogspot.in/2014/02/wpf-layout-controls-scrollviewer.html