Refresh DataGridView when updating data source

Well, it doesn't get much better than that. Officially, you should use

dataGridView1.DataSource = typeof(List); 
dataGridView1.DataSource = itemStates;

It's still a "clear/reset source" kind of solution, but I have yet to find anything else that would reliably refresh the DGV data source.

I ran into this myself. My recommendation: If you have ownership of the datasource, don't use a List. Use a BindingList. The BindingList has events that fire when items are added or changed, and the DataGridView will automatically update itself when these events are fired.