Thanks for your update. We have checked the provided sample and we are a little bit unclear with your requirement.
We suspect that your requirement it to update the details in the property grid immediately after updating the values by clicking the Accept Changes button. If yes, you have to refresh the property grid SelectedObject on Accept Changes button click same as you performed in SelectionChanged event.
If your requirement is to update the details in property grid only after clicking on the corresponding row, there is no need to set SelectedItem property in the CellDoubleClick event. Remove the code to set SelectedItem. So that the SelectionChanged event will be raised and the property grid will update properly.
Please let us know if we have misunderstood your requirement.