SELECT [o].[PartNumber], [o].[CreatedOn]
FROM [Order].[OrderDetail] AS [o]
INNER JOIN [Order].[OrderHeader] AS [o.OrderHeader] ON [o].[OrderHeaderID] = [o.OrderHeader].[OrderHeaderID]
WHERE [o.OrderHeader].[WebUserID] = @__user_WebUserID_0
ORDER BY [o].[PartNumber], [o].[CreatedOn]


SELECT top 5 partnumber, o.createdon
FROM [Order].[OrderHeader] AS [o]
LEFT JOIN [Order].[OrderDetail] AS [o.OrderDetail] ON [o].[OrderHeaderID] = [o.OrderDetail].[OrderHeaderID]
WHERE [o].[WebUserID] = 12
Group By Partnumber, o.createdon
order by o.createdon DESc

 var partNumbers2 = await _orderContext.OrderDetail
                .Where(o => o.OrderHeader.WebUserID == user.WebUserID)
                .Select(o => new OrderDetail { PartNumber = o.PartNumber, CreatedOn = o.CreatedOn })
                .GroupBy(o => new { o.PartNumber, o.CreatedOn })
                .OrderBy(o => o.Key.CreatedOn)
                .Take(8)
                .ToListAsync();