Convert ICollection

Question

I try fill property type of ICollection<Person> or ICollection<T> .I give an objectList type of List<object> or ICollection<object> anyway i can't set value property type of ICollection<Person> by list of object

if (property.PropertyType.IsGenericType &&
     property.PropertyType.GetGenericTypeDefinition()
       == typeof(ICollection<>))
   {

      Type itemType = property.PropertyType.GetGenericArguments()[0];
      ICollection<object> objectList =GetObjectList();
      property.SetValue(item, objectList);


   }

thanks.

@DavidG: the `property` is an `ICollection`, but you can't issue `SetValue` with an object of `ICollection — Mike Perrenoud, May 31 '14 at 12:18
`ICollection` isn't contravariant. You can't set `ICollection` to `ICollection — Yuval Itzchakov, May 31 '14 at 12:21
Also, what is the context ? Do you really need this ? Getting over the types system is usually a sign of bad design. — quantdev, May 31 '14 at 12:41

Yuval Itzchakov · Accepted Answer · 2014-05-31T12:40:05.697

1

You can't set an ICollection<Person> to an ICollection<object> since ICollection isn't contravariant (there is no in keyword in the generic parameter declaration).

You will explicitly have to cast the collection of object to Person

if (property.PropertyType.IsGenericType &&
 property.PropertyType.GetGenericTypeDefinition()
   == typeof(ICollection<>))
{
  Type itemType = property.PropertyType.GetGenericArguments()[0];
  ICollection<Person> objectList =GetObjectList().Cast<ICollection<Person>>();
  property.SetValue(item, objectList);
}

edited May 31 '14 at 12:40

answered May 31 '14 at 12:32

Yuval Itzchakov

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ICollection is example , in actual ,that is anonymoustype but i can accecc to the type of property by itemType (not anyway to ICollection) – Amir Movahedi May 31 '14 at 12:52
@Amirhossein You can't recreate an anonymous type after casting to `object`. You will need to return a strong type – Yuval Itzchakov May 31 '14 at 13:17
but I have itemType (Type itemType = property.PropertyType.GetGenericArguments()[0];) should be away add object to list – Amir Movahedi May 31 '14 at 13:30
So what? You have the `itemType` but still construct a `ICollection – Yuval Itzchakov May 31 '14 at 13:51
1

You can try automapper.org – Yuval Itzchakov May 31 '14 at 20:07
ohh dude that really helped me! thankx... here's 10 points reward. – Amir Movahedi Jun 01 '14 at 07:42

score 0 · Answer 2 · edited May 23 '17 at 12:20

0

Your solution is LINQ, use method OfType or Cast to cast or select objects of specified type. Since you may not convert the ICollection<object> to ICollection<Person> directly but you have a workaround to achieve the same.

ICollection<Person> objectList = GetObjectList().OfType<Person>().ToList();

or

ICollection<Person> objectList = GetObjectList().Cast<Person>().ToList();

This piece of code would return you a List<Person> and since List<T> implements ICollection<T> which means ICollection<Person> here so result will be assignable to your property

in most cases Cast() perform faster then OfType() as there is additional a type check is involved in OfType. read this for more info When to use Cast() and Oftype() in Linq

Update

  object objectList = GetObjectList();
  property.SetValue(item, Convert.ChangeType(objectList, property.PropertyType));

this will convert the value if the types are compatible. this example does not require you to know the underlying type. read more about ChangeType http://msdn.microsoft.com/en-us/library/dtb69x08.aspx

edited May 23 '17 at 12:20

Community

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answered May 31 '14 at 12:31

pushpraj

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I cant access to the strong type (Person)! – Amir Movahedi Jun 02 '14 at 10:46
do you look forward to know the type as well? or you just want to set the return value of GetObjectList()? – pushpraj Jun 02 '14 at 11:51
set the return value of GetObjectList() – Amir Movahedi Jun 02 '14 at 13:44
Yes u right,Thanks but i accepted the other answer(better for me) ,I set vote up for u – Amir Movahedi Jun 02 '14 at 16:03
I should implement IConvertible to use `Convert.ChangeType` for each class. Is there a way to do it automatic and override class for example. – Amir Movahedi Jun 02 '14 at 16:13

2 Answers2