Ordering lists within a list in C#

Question

I need a push in the right direction with regards to ordering data using Linq.

I've got a list of People objects in C#, which in turn, holds a list of Sites that the person may be associated with.

Those Site objects holds is an instance of an Organisation object, that the site is associated with (as an organisation may have many sites..)

Edit: A person will only belong to a single organisation in the list. (Thanks @jonskeet)

How do I order the list of people, using Linq (or Lamba) to show them in alphabetical order, by their Organisation, and then ordered by the Surname, Firstname of the contact..??

Your requirements are unclear - what if a person belongs to more than one organization? Which should be used for sorting? — Jon Skeet
– Jon Skeet, Commented Aug 4, 2011 at 14:03
Ah, beg your pardon. The person will only belong to one organisation. — Brett Rigby
– Brett Rigby, Commented Aug 4, 2011 at 14:04
So why does a Person have a list of sites? It seems that the organization should be set on the person, not on each of the sites... — Jon Skeet
– Jon Skeet, Commented Aug 4, 2011 at 14:08

Jon Skeet · Accepted Answer · 2011-08-04 14:09:41Z

3

It strikes me that your model is a bit messed up, but if you're sure that:

A person will have at least one site
All the sites for a particular person will be for the same organization

you can use:

var sorted = people.OrderBy(p => p.Sites.First().Organization)
                   .ThenBy(p => p.LastName)
                   .ThenBy(p => p.FirstName);

answered Aug 4, 2011 at 14:09

Jon Skeet

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4 Comments

Brett Rigby Over a year ago

It is a bit messed up, but that's another story! :-/

Brett Rigby Over a year ago

Close enough! Here's what I've had to use (for anyone else's reference):

Brett Rigby Over a year ago

sorted = people.OrderBy(x => x.Sites.FirstOrDefault().Organisation.Name).ThenBy(x => x.Surname).ThenBy(x => x.Firstname);

Jon Skeet Over a year ago

@Brett: You shouldn't use FirstOrDefault - that implies there could be an empty list of sites, in which case you'll end up with a null reference which will still go bang, but in a less obvious way.

Dean Chalk · Accepted Answer · 2011-08-04 14:05:30Z

0

people.SelectMany(p => p.Sites).OrderBy(s => s.Organisation.Name).ThenBy(s => s.Organisation.Contact.Surname).ThenBy(s => s.Organisation.Contact.FirstName);

answered Aug 4, 2011 at 14:05

Dean Chalk

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1 Comment

Brett Rigby Over a year ago

Thanks for this, but there's a list of Site objects in between the person and the organisation...

BBC · Accepted Answer · 2011-08-04 14:31:16Z

0

Linq supports an order by clause. Check out this MSDN link

http://msdn.microsoft.com/en-us/library/bb383982.aspx

Example

public class CityLookup
{       public string City { get; set; }    
    public string Country { get; set; }
}

List<CityLookup> citiesLkp =            
new List<CityLookup>            
{       
    new CityLookup{ City = "New Delhi", Country = "India" },          
    new CityLookup{ City = "Sydney", Country = "Australia" },  
    new CityLookup{ City = "Tokyo", Country = "Japan" },                 
    new CityLookup{ City = "New York", Country = "USA" },                
    new CityLookup{ City = "Paris", Country = "France" },                
    new CityLookup{ City = "Barcelona", Country = "Spain" },                                          
};


// Now sort the names based on city name
var myList =    from c in citiesLkp    orderby c.City    select c;

foreach (var record in myList )    
{        
    Console.WriteLine(record.City);    
}

edited Aug 4, 2011 at 14:31

answered Aug 4, 2011 at 14:06

BBC

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1 Comment

Dan Abramov Over a year ago

Is there anything else you can add? A code sample, maybe? Generally answers here are expected to be self-contained.

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