How To Sort A List With Dynamic Objects

Question

I have a list that holds objects of type dynamic. When I use the LINQ OrderBy method, I get an error saying 'object' does not contain a definition for 'Date'. What can I do to sort my list by the date?

List<dynamic> employees = new List<dynamic>();

employees.Add(new
{
    ID = 1,
    Name = "Larry",
    Date = new DateTime(2010, 10, 1),
});

employees.Add(new
{
    ID = 2,
    Name = "Clint",
    Date = new DateTime(2011, 5, 28),
});

employees.Add(new
{
    ID = 3,
    Name = "Jason",
    Date = new DateTime(2011, 7, 6),
});

var query = employees.OrderBy(x => x.Date);

You are saying lambda expressions don't support dynamics?

zmbq
– zmbq

2011-12-06 17:40:29 +00:00
Commented Dec 6, 2011 at 17:40 — zmbq
– zmbq, Commented Dec 6, 2011 at 17:40
In LinqPad it executes and works well.

okrumnow
– okrumnow

2011-12-06 17:40:53 +00:00
Commented Dec 6, 2011 at 17:40 — okrumnow
– okrumnow, Commented Dec 6, 2011 at 17:40

Michael Stum · Accepted Answer · 2011-12-06 17:44:00Z

6

Is the code that you've shown in the same Assembly?

Anonymous Types won't work across assemblies, and the "Object doesn't contain this definition" error is a typical sign of using an anonymous type from two different assemblies

(e.g., in an ASP.net MVC page the Controller may return an anonymous type as a model and the View may try to use it => blows up with exactly that error)

answered Dec 6, 2011 at 17:44

Michael Stum

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2 Comments

Halcyon Over a year ago

Indeed the code is in another assembly. The code I posted was an example. Knowing that it won't work across assemblies, I was able to modify the code that creates the list of dynamic objects to sort by the date and then pass the sorted list to the consuming assembly. Thanks for the info!

Michael Stum Over a year ago

@Halcyon Cool. The problem is that anon types are internal. There are some hacks that wrap them in a dynamic which allows them to work across assemblies, but indeed it's better to rearchitect the solution.

Sergey Kalinichenko · Accepted Answer · 2011-12-06 17:40:35Z

3

I verified that your query works in .NET 4.0. Are you missing a reference to Microsoft.CSharp from your assembly?

answered Dec 6, 2011 at 17:40

Sergey Kalinichenko

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