I am having an issue with grouping, if I group by a column that contains a null value all is fine in this case the middle names have a lot of nulls, but if I group by another column afterwards I get a crash, InvalidOpertationException Collection was modified; enumeration operation may not execute. I am using entity framework bound directly to the grid. Simple code below attached to an older version of adventure works, but anything with a column with nulls in it should work. Just xaml. Curious how to fix this or am I doing something completely wrong somewhere else?