ItemNotNullAttribute Class

Can be applied to symbols of types derived from IEnumerable as well as to symbols of Task and Lazy classes to indicate that the value of a collection item, of the Task.Result property or of the Lazy.Value property can never be null.

[AttributeUsageAttribute]
public sealed class ItemNotNullAttribute : Attribute

<AttributeUsageAttribute> _
Public NotInheritable Class ItemNotNullAttribute _
	Inherits Attribute

[AttributeUsageAttribute]
public ref class ItemNotNullAttribute sealed : public Attribute

public void Foo([ItemNotNull]List<string> books)
{
foreach (var book in books) {
if (book != null) // Warning: Expression is always true
Console.WriteLine(book.ToUpper());
}
}