Why ListItem must be declared explicitly in foreach C#

Question

I'm confused as to why this code would not compile if listControl is a ListControl object such as a DropDownList:

foreach (var item in listControl.Items) {
    item.Value = string.empty;
}

The compiler considers item to be of type object. It works if I replace var with ListItem, declaring the variable explicitly. The Items property is a ListItemCollection, which implements IEnumerable. Shouldn't the compiler be able to tell that the objects in the collection are of type ListItem?

Answer 1

This is a strange behavior since, as you point out, ListItemCollection is a collection of ListItems. This appears related to the fact that this was implemented before C# supported generics. And so it implements IEnumerable instead of IEnumerable<ListItem>, and isn't able to determine the correct type.

I suggest rewriting your loop this way:

foreach (ListItem item in listControl.Items) {
    item.Value = string.empty;
}

Check out this question for additional information.