Multiple Order By with LINQ [duplicate]

Question

I start with a basic class that I want to manipulate in a List using LINQ, something like the following:

public class FooBar   
{  
    public virtual int Id { get; set; }  
    public virtual string Foo { get; set; }  
    public virtual string Bar { get; set; }
}

This is what I ultimately found out to solve my problem using the non lambda LINQ stuff.

// code somewhere else that works and gets the desired results  
var foobarList = GetFooBarList();  // Abstracted out - returns List<Foobar>  

// Interesting piece of code that I want to examine
var resultSet = from foobars in foobarList  
                orderby foobars.Foo, foobars.Bar  
                select foobars;

// Iterate and do something interesting  
foreach (var foobar in resultSet)  
{  
    // Do some code  
}

What I'm really curious about is if the same can be accomplished using the Lambda based extension methods off of generic IEnumerable to accomplish the same thing. Google tells me I can do something like the following to accomplish it:

var resultSet = foobarList.OrderBy(x => new {x.Foo, x.Bar})  
                          .Select(x=>x);

However if I do that I get a runtime error when I hit the foreach statement. The error tells me that at least one object has to implement IComparible, which I can see that since I'm using an anonymous type for the .OrderBy() method.

So is there a way to accomplish what I want using the Lambda way?

If you want to know what the "fluent methods" are corresponding to every possible query expression, read section 7.15.2 of the specification. — Eric Lippert
– Eric Lippert, Commented Feb 23, 2010 at 16:28
@Eric Lippert, there's a C# 3.0 Query Expression Translation Cheat Sheet, written by Bart Desmet, which I found very useful as a quick reference: bartdesmet.net/blogs/bart/archive/2008/08/30/… . — Pop Catalin
– Pop Catalin, Commented Feb 24, 2010 at 22:11

Keidax · Accepted Answer · 2013-07-09 15:09:33Z

622

You can use the ThenBy and ThenByDescending extension methods:

foobarList.OrderBy(x => x.Foo).ThenBy( x => x.Bar)

edited Jul 9, 2013 at 15:09

Keidax

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answered Feb 23, 2010 at 14:37

Pop Catalin

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7 Comments

sdanna Over a year ago

Guess I should fully get through the API before asking the question ;) It also looks like you can chain .ThenBy() statements as many times as you need to. Thanks again!

Brock Hensley Over a year ago

what about .AndThen()

Valamas Over a year ago

No .AndThen()!

masteroleary Over a year ago

(function AndThen() { AndThen() })()

Kurtis Jungersen Over a year ago

NOTE: .OrderBy() and .ThenBy() return an IOrderedEnumerable, which does not modify the original object. So, you need to assign to a variable and end with ToList() to use the new ordered list elsewhere.

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