LINQ: Get all selected values of a CheckBoxList using a Lambda expression

You are using lambda expressions – they are just concealed by your use of C#’s query operators.

Consider that this:

IEnumerable<int> allChecked = (from item in chkBoxList.Items.Cast<ListItem>() 
                               where item.Selected 
                               select int.Parse(item.Value));

Gets compiled to this:

IEnumerable<int> allChecked = chkBoxList.Items.Cast<ListItem>()
                              .Where(i => i.Selected)
                              .Select(i => int.Parse(i.Value));

As you can see you are already using two lambda expressions (they are the parameters to the Where and Select methods) and you didn’t even know it! This query is fine and I wouldn’t change it at all.