You can use ScrollChangedEventArgs.ExtentHeightChange to know if a ScrollChanged is due to a change in the content or to a user action…
When the content is unchanged, the ScrollBar position sets or unsets the auto-scroll mode.
When the content has changed you can apply auto-scrolling.
Code behind:
private Boolean AutoScroll = true;
private void ScrollViewer_ScrollChanged(Object sender, ScrollChangedEventArgs e)
{
// User scroll event : set or unset auto-scroll mode
if (e.ExtentHeightChange == 0)
{ // Content unchanged : user scroll event
if (ScrollViewer.VerticalOffset == ScrollViewer.ScrollableHeight)
{ // Scroll bar is in bottom
// Set auto-scroll mode
AutoScroll = true;
}
else
{ // Scroll bar isn't in bottom
// Unset auto-scroll mode
AutoScroll = false;
}
}
// Content scroll event : auto-scroll eventually
if (AutoScroll && e.ExtentHeightChange != 0)
{ // Content changed and auto-scroll mode set
// Autoscroll
ScrollViewer.ScrollToVerticalOffset(ScrollViewer.ExtentHeight);
}
}