OnVScroll() get call twice?

[Eugene]

can anybody tell why OnVScroll()/OnHScroll() will get called twice whenever an scroll event has occurred ?

Once for the action e.g SB_PAGEUP

Once for the end scroll event i.e SB_ENDSCROLL

I don't recall the details, but put a breakpoint at the first line in the VScroll or HScroll method handler and examine all of the parameter values. For each call, the set of parameter values are different.

[Eugene]

I've examine the value of the parameter and i known it is different each time it get called, but i want to know why it get call twice?