Adding new dynamic properties-Collection of common programming errors

When using DynamicObject as your base class, you should provide specific overrides to TryGetMember and TrySetMember to keep track of the dynamic properties you are creating (based on the DynamicObject MSDN documentation):

class DemoDynamicObject: DynamicObject
{
    Dictionary dictionary
        = new Dictionary();

    public override bool TryGetMember(
        GetMemberBinder binder, out object result)
    {
        string name = binder.Name;
        return dictionary.TryGetValue(name, out result);
    }

    public override bool TrySetMember(
        SetMemberBinder binder, object value)
    {
        dictionary[binder.Name] = value;
        return true;
    }
}

If you just want to have a dynamic object that you can add properties to, you can simply use an ExpandoObject instance, and skip the custom class inheriting from DynamicObject.