Enumerable OrderBy - are null values always treated high or low and can this be considered stable behaviour?

Question

I am sorting some IEnumerable of objects:

var sortedObjects = objects.OrderBy(obj => obj.Member)

Where Member is of an IComparable type. This sort seems to put objects with obj.Member == null at the top. This is roughly the behaviour that I want, but can I consider this to be stable with respect to future .NET frameworks? Is there a way I can make this 'nulls are low' behaviour more explicit?

Answer 1

To make the behavior more explicit:

var sorted = objects.OrderBy(o => o.Member == null).ThenBy(o => o.Member);

Answer 2

From MSDN for IComparable:

By definition, any object compares greater than (or follows) null, and two null references compare equal to each other.

So a null object is considered less than a non-null object. If sorting ascending, you will get nulls first.

Answer 3

One option is to use the overload of OrderBy that takes an IComparer<T> and implement it yourself to codify this expectation:

http://msdn.microsoft.com/en-us/library/bb549422.aspx