LINQ OrderBy: best search results at top of results list

linq, linq-to-objects, sorting

Solution

Use `Select` to project a "match evaluation" with the customer, and then order by that:

class Program
{
    static void Main(string[] args)
    {
        var Customers = new Customer[]
        {
            new Customer { FirstName = "Foo", LastName = "Laurie" },
            new Customer { FirstName = "Bar", LastName = "Jackson" },
            new Customer { FirstName = "Jackson", LastName = "Bro" },
            new Customer { FirstName = "Laurie", LastName = "Foo" },
            new Customer { FirstName = "Jackson", LastName = "Laurie" },
        };

        string[] searchTerms = new string[] { "Jackson", "Laurie" };

        //want to find those customers with first, last or BOTH names in the searchTerms 
        var matchingCusts = Customers
                               .Where(m => searchTerms.Contains(m.FirstName)
                                       || searchTerms.Contains(m.LastName))
                               .ToList();

        var result = matchingCusts.Select(x => new
            {
                Customer = x,
                MatchEvaluation = (searchTerms.Contains(x.FirstName) ? 1 : 0) + (searchTerms.Contains(x.LastName) ? 1 : 0),
            })
            .OrderByDescending(x => x.MatchEvaluation)
            .Select(x => x.Customer);

        foreach (var c in result)
        {
            Console.WriteLine(c.FirstName + " " + c.LastName);
        }

        Console.ReadKey();
    }

    public sealed class Customer
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
    }
}

Problem

Consider the need to search a list of Customer by both first and last names. The desire is to have the results list sorted by the Customer with the most matches in the search terms. ``` FirstName LastName ---------- --------- Foo Laurie Bar Jackson Jackson Bro Laurie Foo Jackson Laurie ``` ``` string[] searchTerms = new string[] {"Jackson", "Laurie"}; //want to find those customers with first, last or BOTH names in the searchTerms var matchingCusts = Customers .Where(m => searchTerms.Contains(m.FirstName) || searchTerms.Contains(m.LastName)) .ToList(); /* Want to sort for those results with BOTH FirstName and LastName matching in the search terms. Those that match on both First and Last should be at the top of the results, the rest who match on one property should be below. */ return matchingCusts.OrderBy(m=>m); ``` Desired Sort: ``` Jackson Laurie (matches on both properties) Foo Laurie Bar Jackson Jackson Bro Laurie Foo ``` How can I achieve this desired functionality with LINQ and `OrderBy` / `OrderByDescending`?

Original source