Make dictionary read only in C#

Question

I have a Dictionary> and would like to expose the member as read only. I see that I can return it as a IReadOnlyDictionar

Answer 1

If you want to return a read only dictionary but still be able to mutate the dictionary and list in your class you could use casting to get back the list type.

This example is a bit contrived, but shows how it could work.

public class MyClass
{
    Dictionary> _dictionary;
    public IReadOnlyDictionary> Dictionary { get { return _dictionary; } }

    public MyClass()
    {
        _dictionary = new Dictionary>();
    }

    public void AddItem(string item)
    {
        IReadOnlyList readOnlyList = null;
        List list = null;
        if (!_dictionary.TryGetValue(item, out readOnlyList))
        {
            list = new List();
            _dictionary.Add(item, list);
        }
        else
            list = readOnlyList as List;
        list.Add(item);
    }
}

If you goal is to have the property be immutable, then using a ReadOnlyDictionary would be the best option.