Hi, 

That's b/c the grouping can't resolve. Setting the value to "Motion" tells the data source to look for a property called Motion on your data object. However your data object doesn't even expose any properties. 

The easiest solution for you would simply to be to add a grouping property to your cSimpleGrid object:

[Export("group")]
        public string Group
        {
            get 
            {
                return this["Motion"].ToString();
            }
        }

Then you would set the grouping key to be "group"

dsh.GroupingKey = "group";

It's very important that you export that property. And also to use whatever value you use for the export as the GroupingKey. 

It's worth noting, that while i hardCoded "Motion" into the data object, you wouldn't necessarily have to do that. The grouping key could be a value you pass into the ctor of cSimpleGrid so that it could be more by dynamic. 

Hope this helps. 

-SteveZ