Thanks for the reply.
For my application, the X-Axis will be the time.
The user required to get the value of Y-Axis and the time of X-Axis on the chart on any point of the line. For emaple, in the mid-point between 10 and 20, the user expects to get the value 15 and 9.5
If mouseover is not possible, can onClick meet the requirement?
Or can we use the height and width of the PlotArea to calculate the x and y coordinate and get the answer?