Conversion of object List to Generic List

Question

I have a List of object came to me by serialization. But I know following:

The list is not Empty
All types of the list have the same type. I can know this type only dynamically. For example:

list[0].GetType()

How to convert all list to Generic List using above mentioned conditions ?

P.S. I deserialize an array of objects came to me in JSON

    {
   "Message": [
      {
         "__type": "GameResponse:#Bridge3.Server",
         "GameId": 1,
         "GameName": "Game1                                  ",
         "PlayerId": 1
      },
      {
         "__type": "GameResponse:#Bridge3.Server",
         "GameId": 2,
         "GameName": "Game2                                  ",
         "PlayerId": 1
      }
    }

You can't. Change the serialization code to return the proper strongly typed data. — Fede
– Fede, Commented Mar 12, 2014 at 21:43
You can make a generic list by reflection. But what is your usage about? What do you want to do with generated generic list? Explain more please. — amiry jd
– amiry jd, Commented Mar 12, 2014 at 21:46
@javad_amiry if the type were know at compile time, you can just list.OfType<TheType>(). However, the OP's apparent situation is that the type is unknown at compile time — Fede
– Fede, Commented Mar 12, 2014 at 21:46
@Javad_Amiry which makes no sense whatsoever, since you're already dealing with a list of unkown objects, you better treat them as dynamic in that case. No need for reflection, unless you want to convert the data to some sort of Dictionary<string,object> such as a DataTable or the like. — Fede
– Fede, Commented Mar 12, 2014 at 21:50
Yes again, and it is the why of my question: What is usage? — amiry jd
– amiry jd, Commented Mar 12, 2014 at 21:52

Grozz · Accepted Answer · 2014-03-12 21:57:25Z

2

You can use somewhat of a workaround with the magic of dynamic keyword:

interface ICar {}
interface IAnimal {}

class Program
{
    static void Dispatch(dynamic list)
    {
        Console.WriteLine("Dispatch called");
        DoSomething(list);
    }

    static void DoSomething<T>(List<T> genericList)
    {
        Console.WriteLine("Generic unconstrained method called");
    }

    static void DoSomething(List<IAnimal> animalList)
    {
        Console.WriteLine("Do something WILD");
    }

    static void DoSomething(List<ICar> carList)
    {
        Console.WriteLine("Calculate loans");
    }

    static void Main()
    {
        object deserializedList = new List<ICar>();
        Dispatch(deserializedList);
    }
}

answered Mar 12, 2014 at 21:57

Grozz

8,4555 gold badges41 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

alerya Over a year ago

static void DoSomething<T>(List<T> genericList) will use List<object> :) No need for dynamic

payo Over a year ago

@alerya but with DoSomething<T> you don't have type; you can't use the methods. This is a nice way of giving you all the type info. (sans reflection)

payo · Accepted Answer · 2014-03-12 22:14:45Z

1

You can use reflection to create a strong typed list. You won't have that type for use in code, but the list type will be fixed.

//DetermineSerializedType here would be your own method to determine the type you have
Type deserializedType = DetermineSerializedType(serializedData);

Type genericType = typeof(List<>).MakeGenericType(deserializedType);
ConstructorInfo ctor = genericType.GetConstructor(new Type[] { });
object inst = ctor.Invoke(new object[] { });
IList list = inst as IList;

EDIT Personally I think the dynamic solution Grozz gives is cleaner.

edited Mar 12, 2014 at 22:14

answered Mar 12, 2014 at 21:54

payo

4,5711 gold badge26 silver badges33 bronze badges

3 Comments

Fede Over a year ago

how is this any better than an object[] ?

gretro Over a year ago

And use the Activator to create an instance of the generic list type. I had to create a custome Serializer and this works.

payo Over a year ago

@HighCore Because he didn't ask for an object[]

Collectives™ on Stack Overflow

Conversion of object List to Generic List

2 Answers 2

2 Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related