Find out deselected item in a CheckBoxList ASP.NET

I have a CheckBoxList with a SelectedIndexChanged event, where I add the Value of the 开发者_开发问答selected ListItem to a variable. I want to substract the Value when the item is unchecked.

I tried SelectedIndex but returns -1 and SelectedItem returns null. And the EventArgs argument doesn't have any data to help...

You should use the Items property. In other words, your variable should start with its value set to whatever it should be before applying the selected items. Then, iterate over the items, applying your logic against the variable one item at a time for each item that is selected. Then, no matter what the user selects or de-selects, you'll always arrive at the proper value for your variable.

int myValue = 0;

foreach(ListItem item in cbl.Items)
{
    if(item.Selected) myValue += int.Parse(item.Value);
}