How can I catch a double-click into a column header cell

You can use the DataGrid’s double-click event and its HitTest method to catch a double click on a header.

	private void dataGrid1_DoubleClick(object sender, System.EventArgs e)
	{
		System.Drawing.Point pt = dataGrid1.PointToClient(Cursor.Position);

		DataGrid.HitTestInfo hti = dataGrid1.HitTest(pt);

		if(hti.Type == DataGrid.HitTestType.ColumnHeader) 
		{
			MessageBox.Show('double clicked clicked column header ' + hti.Column.ToString());
		}
	}