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 do need this. You'll get an exception when foreach accesses the container to set up the iteration otherwise.

Under the covers, foreach uses an interface implemented on the collection class to perform the iteration. The generic equivalent interface is here.

The foreach statement of the C# language (for each in Visual Basic) hides the complexity of the enumerators. Therefore, using foreach is recommended instead of directly manipulating the enumerator.