Just as a slight cosmetic addition to Rune’s suggestion, you could create your own extension method:
public static IEnumerable<T> OrEmptyIfNull<T>(this IEnumerable<T> source)
{
return source ?? Enumerable.Empty<T>();
}
Then you can write:
foreach (var header in file.Headers.OrEmptyIfNull())
{
}
Change the name according to taste 🙂