Linq OrderBy against specific values

by

If you put your preferences into a list, it might become easier.

List<String> data = new List<String> { "A","B","A","C","B","C","D","E" };
List<String> preferences = new List<String> { "A","B","C" };

IEnumerable<String> orderedData = data.OrderBy(
   item => preferences.IndexOf(item));

This will put all items not appearing in preferences in front because IndexOf() returns -1. An ad hoc work around might be reversing preferences and order the result descending. This becomes quite ugly, but works.

IEnumerable<String> orderedData = data.OrderByDescending(
   item => Enumerable.Reverse(preferences).ToList().IndexOf(item));

The solution becomes a bit nicer if you concat preferences and data.

IEnumerable<String> orderedData = data.OrderBy(
   item => preferences.Concat(data).ToList().IndexOf(item));

I don’t like Concat() and ToList() in there. But for the moment I have no really good way around that. I am looking for a nice trick to turn the -1 of the first example into a big number.

More Related Contents:

  1. property remove from the list
  2. Dynamic LINQ OrderBy on IEnumerable / IQueryable
  3. Remove duplicates in the list using linq
  4. Sorting a list using Lambda/Linq to objects
  5. How can I get LINQ to return the object which has the max value for a given property? [duplicate]
  6. LINQ to SQL and a running total on ordered results
  7. Linq select objects in list where exists IN (A,B,C)
  8. Find() vs. Where().FirstOrDefault()
  9. Linq to Objects – return pairs of numbers from list of numbers
  10. C# Linq where clause as a variable
  11. LINQ identity function
  12. Code equivalent to the ‘let’ keyword in chained LINQ extension method calls
  13. linq to entities vs linq to objects – are they the same?
  14. Difference Between Select and SelectMany
  15. Distinct by property of class with LINQ [duplicate]
  16. What’s the hardest or most misunderstood aspect of LINQ? [closed]
  17. C# – code to order by a property using the property name as a string [duplicate]
  18. LEFT JOIN in LINQ to entities?
  19. Can I specify my explicit type comparator inline?
  20. linq where list contains any in list
  21. Entity Framework (.NET Full Framework) Ordering Includes [duplicate]
  22. How to compare only date components from DateTime in EF?
  23. Entity Framework 6 Code First Custom Functions
  24. Merge multiple Lists into one List with LINQ
  25. Order by dynamic parameter
  26. Compare Two Lists Via One Property Using LINQ
  27. Should the order of LINQ query clauses affect Entity Framework performance?
  28. Transform IEnumerable asynchronously by awaiting each task
  29. Map two lists into a dictionary in C#
  30. How to check if all list items have the same value and return it, or return an “otherValue” if they don’t?

Leave a Comment