Working with C# Anonymous Types

Question

I am calling a method that returns a List variable that contains a c# Anonymous Type objects. For example:

List<object> list = new List<object>();
foreach ( Contact c in allContacts ) {
    list.Add( new {
        ContactID = c.ContactID,
        FullName = c.FullName
    });
}
return list;

How do I reference this type properties in the code I am working on like for example

foreach ( object o in list ) {
    Console.WriteLine( o.ContactID );
}

I know that my sample is not possible, I have only wrote that way to say that I need to identify each property of the anonymous type exactly.

Thanks!

Solution:

Not just one of the answer is correct and/or suggest a working solution. I have ended up to using Option 3 of Greg answer. And I learned something very interesting regarding the dynamic in .NET 4.0!

Answer 1

You can't return a list of an anonymous type, it will have to be a list of object. Thus you will lose the type information.

Option 1
Don't use an anonymous type. If you are trying to use an anonymous type in more than one method, then create a real class.

Option 2
Don't downcast your anonymous type to object. (must be in one method)

var list = allContacts
             .Select(c => new { c.ContactID, c.FullName })
             .ToList();

foreach (var o in list) {
    Console.WriteLine(o.ContactID);
}

Option 3
Use the dynamic keyword. (.NET 4 required)

foreach (dynamic o in list) {
    Console.WriteLine(o.ContactID);
}

Option 4
Use some dirty reflection.