Question

I have two generic list objects, in which one contains ids and ordering, and the other a bunch of ids with each id in the second list having an id reference to the first list, for example;

public class OptionType
{
    public int ID { get; set; }
    public int Ordering { get; set; }
}

public class Option
{
    public int ID { get; set; }
    public int Type_ID { get; set; }
}   

Obviously I can do a simple sort on a list of OptionTypes by doing

types_list.OrderBy(x => x.Ordering);

Question is though, how could I go about ordering an ‘options_list’ by utilising the ‘Type_ID’ on the object which would relate to the ordering of the types_list. As in something like (obviously this isn’t valid – but hopefully you will get the idea!)

options_list.OrderBy(x => x.Type_ID == types_list.OrderBy(e => e.Ordering));

Answer 1

You should be able to use a join to produce your desired output. Example using query syntax.

var orderedOptions = from option in options_list
                     join type in types_list
                     on option.Type_ID equals type.ID
                     orderby type.Ordering
                     select option;