Is if(items != null) superfluous before foreach(T item in items)?

Question

I often come across code like the following:

if ( items != null)
{
   foreach(T item in items)
   {
        //...
   }
}

Basically, the

Answer 1

You still need to check if (items != null) otherwise you will get NullReferenceException. However you can do something like this:

List items = null;  
foreach (var item in items ?? new List())
{
    item.Dump();
}

but you might check performance of it. So I still prefer having if (items != null) first.

Based on Eric's Lippert suggestion I changed code to:

List items = null;  
foreach (var item in items ?? Enumerable.Empty())
{
    item.Dump();
}