Question

Using reflection, I am trying to grasp onto a class fields and populate them. Currently I have it detecting an instance of a Dictionary<,> and creating a Dictionary<object,object> to fill. Afterwards its tries to change the type, however this does not work and fails casting:

// Looping through properties. Info is this isntance.
// Check is a dictionary field.
Dictionary<object, object> newDictionary = new Dictionary<object, object>();

// Populating the dictionary here from file.
Type[] args = info.PropertyType.GetGenericArguments();
info.GetSetMethod().Invoke(data, new object[]
    {
        newDictionary.ToDictionary(k => Convert.ChangeType(k.Key, args[0]),
                                   k => Convert.ChangeType(k.Value, args[1]))
    });

Any ideas? Thanks.

Answer 1

You should create dictionary manualy of type you found.

Type dictionary = typeof(Dictionary<,>);
Type[] typeArgs = info.PropertyType.GetGenericArguments();

// Construct the type Dictionary<T1, T2>.
Type constructed = dictionary.MakeGenericType(typeArgs);
IDictionary newDictionary = (IDictionary)Activator.CreateInstance(constructed);

// Populating the dictionary here from file. insert only typed values below
newDictionary.Add(new object(), new object());


info.SetValue(data, newDictionary, null);

Proof for downvoters.

    static void Main(string[] args)
    {
        IDictionary<int, string> test = new Dictionary<int, string>();
        var castedDictionary = (IDictionary)test;
        castedDictionary.Add(1, "hello");
        Console.Write(test.FirstOrDefault().Key);
        Console.Write(test.FirstOrDefault().Value);
        Console.ReadLine();
    }

Dictionary<TKey, TValue> implements IDictionary, in my example Im creating instance of Dictionary<TKey, TValue> (Type dictionary = typeof(Dictionary<,>);).

public class Dictionary<TKey, TValue> : IDictionary<TKey, TValue>, 
    ICollection<KeyValuePair<TKey, TValue>>, IDictionary, ICollection, 
    IReadOnlyDictionary<TKey, TValue>, IReadOnlyCollection<KeyValuePair<TKey, TValue>>, 
    IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable, ISerializable, 
    IDeserializationCallback