C# Linq Convert Object Property to Array

Question

I have an object that I am converting to JSON to be consumed by Ember.js. Currently I have some child objects that are fully expanded but ember expects just an array of ids on the client side. How can I flatten the object out to be a int[]

items = Mapper.Map<IList<Item>>(client.GetItems());
foreach (var item in items)
{
  int[] choices = item.Choices.Select(x => x.Id).ToArray();

  item.Choices = choices;
}

get an error about not being able to convert to type int[] from IList<Item> how can I cast the property?

example current JSON I produce after serializing

{ "items": [
   {
     "id": 0,
     "name": "Item0",
     "description": "...",
     "choices": [
       { "id": 0, "property": "somevalue" },
       { "id": 1, "property": "somevalue" },
     ]
   },
   {
     "id": 1,
     "name": "Item1",
     "description": "...",
     "choices": [
       { "id": 0, "property": "somevalue" },
       { "id": 1, "property": "somevalue" },
     ]
   }
]}

The JSON I would like to produce

{ "items": [
   {
     "id": 0,
     "name": "Item0",
     "description": "...",
     "choices": [0, 1]
   },
   {
     "id": 1,
     "name": "Item1",
     "description": "...",
     "choices": [0, 1]
   }
]}

Issue is here: item.Choices = choices; item.Choices is of type List and you are trying to assign choices of type int[]. — Poornima
– Poornima, Commented Dec 16, 2013 at 21:32
Yea how can I get around that without creating a completely new class with the only difference that Items is an int[] instead of an IList<>. I want to change the type of that property for this instance of the object. — BillPull
– BillPull, Commented Dec 16, 2013 at 21:34
You don't need to create another class and you cannot change the property type. You can create another property of int[] type in the existing class and use the linq statement in the getter. Something like item.ChoiceIDs? — Poornima
– Poornima, Commented Dec 16, 2013 at 21:36
SelectMany is not going to help you here. You need to make a new class with choices defined as int[] instead of IList<Item> — John Gibb
– John Gibb, Commented Dec 16, 2013 at 21:52

Konstantin · Accepted Answer · 2013-12-16 21:40:30Z

4

SelectMany flattens List of Lists and produces single List with all items.

items.SelectMany(x=>x.Choices.Select(y=>y.Id).ToArray()));

answered Dec 16, 2013 at 21:40

Konstantin

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Poornima · Accepted Answer · 2013-12-16 21:56:26Z

1

get an error about not being able to convert to type int[] from IList how can I cast the property?

You cannot cast one type to another. Instead you can create another property of type int[] in your class and use the LINQ statement in getter (with necessary validation checks).

public int[] ChoiceIDs
{ 
    get {
     return this.Choices.Select(x => x.Id).ToArray();
    }
}

edited Dec 16, 2013 at 21:56

answered Dec 16, 2013 at 21:49

Poornima

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