I am not sure about the the way that you added the columns. This should take place in the PageLoad event handler, following the
rules for a structure object: columns should
be added to the corresponding collection first
and then values
for the properties of this instance should be set.
Please make sure that you have added the columns as explained.
sender, System.EventArgs e)
( !IsPostBack )
//Important: first Add column to the collection
//Then set properties