How VerticalOffset changes when Scrollable height

问题:

I am making a WP7 app which has a Listbox of UserControls. Each UserControl has an ItemsControl and Button(for getting more results). On click of the button the ItemsControl items will be increased by 5 or 10.

Now on clicking on the GetMore button of any of the usercontrols except the first or last, there will be an increase in Scrollable height(Total height of the listbox) of the ListBox but the VerticalOffset(position of scrollbar from top) of the ListBox remains same. Now the problem I am facing is that the Vertical Offset is not absolute but relative to Scrollable Height. So the content being viewed till then will be changed basing on the new value of ScollableHeight.

I want to know the relation between them, so that I can do some math and set the VerticalOffset value.

I have added some dependency properties on VerticalOffset and ScrollableHeight through which I can get the events when any of them is changed. Trying to use ScrollIntoView for readjusting the Vertical Offset

Any suggestions or corrections are highly appreciated.

回答1:

I am not able to find the calculation. But what can be done is listbox can be replaced by a scrollviewer which has itemsControl inside it. But the disadvantage of this is virtualisation is disabled, so will need to check on this.

But, overall this is going to give a bad experience on using such a UserControl in Listbox. So using templated list box given in WP7 toolkit is an option but it is gonna hang a bit since ListBox is not optimized for multi templated virtualization. So I started showing writing listbox item template in such a way it contains all the possible layouts which will enabled from a condition.