IsNull(columnname, replacementValue)
See
http://msdn2.microsoft.com/en-us/library/system.data.datacolumn.expression.aspx

Signature
HTH,
Kevin Spencer
Microsoft MVP
Chicken Salad Shooter
http://unclechutney.blogspot.com
A man, a plan, a canal, a palindrome that has.. oh, never mind.
> How do I specify the filter for a column with NULL value in
> DataTable.Select(filter, sort) function?
>
> string filter = "columnname=NULL"; ?