adding expando properties to a typed object at runtime in c#

Question

Is there any way in .net to bind a dictionary of properties to an instance at runtime, i.e., as if the base object class had a property like:

public IDiction         


        

Answer 1

Have a look at the ConditionalWeakTable<TKey, TValue> Class.

The ConditionalWeakTable<TKey, TValue> class enables language compilers to attach arbitrary properties to managed objects at run time. A ConditionalWeakTable<TKey, TValue> object is a dictionary that binds a managed object, which is represented by a key, to its attached property, which is represented by a value. The object's keys are the individual instances of the TKey class to which the property is attached, and its values are the property values that are assigned to the corresponding objects.

Essentially it's a dictionary where both the keys and the values are weakly referenced, and a value is kept alive as long as the key is alive.

---

static class ExpandoExtensions
{
    private static readonly ConditionalWeakTable<object, ExpandoObject> props =
        new ConditionalWeakTable<object, ExpandoObject>();

    public static dynamic Props(this object key)
    { 
        return props.GetOrCreateValue(key);       
    } 
}

Answer 2

You could use a WeakReference to reference the objects so that they can still be garbage collected. You'll still have to clean up your dictionary by hand though, as the objects themselves are destroyed.