ObservableDictionary for c#

Question

I'm trying to use following implementation of the ObservableDictionary: ObservableDictionary (C#).

When I'm using following code while binding the dictionary to a DataGrid:

ObserveableDictionary<string,string> dd=new ObserveableDictionary<string,string>();
....
dd["aa"]="bb";
....
dd["aa"]="cc";

at dd["aa"]="cc"; I'm getting following exception

Index was out of range. Must be non-negative and less than the size of the 
collection. Parameter name: index

This exception is thrown in CollectionChanged(this, new NotifyCollectionChangedEventArgs(action, newItem, oldItem) in the following method:

private void OnCollectionChanged(NotifyCollectionChangedAction action, KeyValuePair<TKey, TValue> newItem, KeyValuePair<TKey, TValue> oldItem)
{
  OnPropertyChanged();

  if (CollectionChanged != null) CollectionChanged(this, new NotifyCollectionChangedEventArgs(action, newItem, oldItem));
}

The index param seems to correspond to KeyValuePair<TKey, TValue> oldItem.

How can KeyValuePair<TKey, TValue> be out of range, and what should I do to make this work?

Answer 1

Similar data structure, to bind to Dictionary type collection

http://drwpf.com/blog/2007/09/16/can-i-bind-my-itemscontrol-to-a-dictionary/

It provides a new Data structure ObservableDictionary and fires PropertyChanged in case of any change to underlying Dictionary.