Returns the Value that corresponds to the specified mouse position (x, y), relative to the parent control. If the 'dragging' parameter is True the returned value is the result of dragging the pointer from its current position to (x, y).

'宣言
 
Public Overloads Function GetValueAt( _
   ByVal x As System.Integer, _
   ByVal y As System.Integer, _
   ByVal dragging As System.Boolean _
) As System.Double

public System.double GetValueAt( 
   System.int x,
   System.int y,
   System.bool dragging
)