I cannot remember how...
In the development environment I am editing a grid class. (It has one column)
I drag another control to place in the column and I get the error :Cannot add this object to Grid.
I am dragging a control from my base classes to the grid column.
It doesn't matter which one.

I've tried two things.
1. Just select the grid.
2. Select Column First and then drag to grid.

What am I forgetting?
Mike