Question

I am using Linq To Sql as my database layer for the first time and I have run into an issue. Basically, I have a form that allows users to create predefined jobs. A predefined job can have many predefined job items. For example, a predefined job might be something like an oil change. The predefined job items would be oil, labor, etc. In my database PredefinedJobs is a table and PredefinedJobItems is another table with a foreign key back to PredefinedJobs. I have a form for adding predefined jobs that has the Linq-to-Sql class backing the form as a class variable. There is a ListView on the form that displays all of the jobs items. A new feature has required me to track the position of an item in the ListView. For example, if my item ListView looks like below, note the order:

Qty          Name          Desc          ItemOrder
4            Oil           Penzoil       0
1            Labor                       1

Because the items are added via a child form I do not want to provide access to the ListView. So, I created the method below in an attempt to both create the ItemOrder and sort the collection on the PredefinedJob Linq to Sql object. It does not appear that the OrderBy function on the List actually sorts the collection on the PredefinedJob. What would be the best way to maintain order on the Linq to Sql collection (i.e. PredefinedJob.fkJobItems)? Or, would it be better to just pass a reference to my ListView into the child form that adds the items to the jobs where I have access to the selectedIndex?

    private SortAndOrderItems(List<PredefinedJobsItem> items)
    {
        var nextItemOrderNumber = items.Max(max => max.ItemOrder) + 1;
        foreach (var item in items)
        {
            if (item.ItemOrder == null)
            {
                item.ItemOrder = nextItemOrderNumber;
                nextItemOrderNumber++;
            }
        }
        items.OrderBy(i => i.ItemOrder).ToList();
    }

Answer 1

OrderBy creates a new query, that will, when executed, not alter your original list.

Why not just the Sort method of the List?

items.Sort((a, b) => a.ItemOrder.CompareTo(b.ItemOrder));