I put the WPG control in a UserControl and did not set the width and height properties, because I want the
WPG to resize along with its container.But when I ran it , the scroll bar of WPG didn't show up, and middle button of
mouse did not work, so part of the properties can not be seen.
Does the scroll bar of WPG only shows up when the height property is explicitly set?
How to make the scroll bar always visible so I can scroll up and down while WPG can resize along with its container?