private static IEntity[] ConcatenateNullable(IEntity[] a, IEntity[] b)
{
if (a != null && a.Length > 0)
if (b != null && b.Length > 0)
return a.Concat(b).ToArray();
else
return a;
else
if (b != null && b.Length > 0)
return b;
else
return null;
}