linq - How to use isnull type decision in linqdatasource orderby? -

I have a SQL stored procedure, which will be used respectively in order to order items from the date of the latest reply date. , Or the date of posting is zero:

Example: ORDER BY isnull (rtb.LatestReplyDate, CB_TOPIC_DATE_POSTED) DESC

I work it in order according to order of a linqdatasource I have been trying, no benefit till now: Example:

I know that there is no validity there Yes, but I just do not know what will work, if anything. I tried ?? Any ideas as an operator?

- addendum

  orderbie ( P = & gt; P.Litt; YourCompareVariant & gt; == Nil; P. & lt; If Null & gt;: P. & lt; IfNotNull & gt;);  

In your case:

  commandb (p = & gt; p.LatestReplyDate == blank; P. latest delete: p.TopicDatePosted);