As a fan of ObservableCollections, I have created an observable dictionary. I have provided the code below. I have implemented interfaces that should allow for WPF databinding. The reason I needed such a class is because I needed an event to indicate when the dictionary was updated. I kept this class small (it is just a wrapper over a dictionary).
public class ObservableDictionary<TKey, TValue> :
IDictionary<TKey, TValue>,
INotifyCollectionChanged,
INotifyPropertyChanged
{
public event NotifyCollectionChangedEventHandler CollectionChanged;
public event PropertyChangedEventHandler PropertyChanged;
readonly IDictionary<TKey, TValue> _dictionary = new Dictionary<TKey, TValue>();
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
return _dictionary.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
public void Add(KeyValuePair<TKey, TValue> item)
{
_dictionary.Add(item);
if (CollectionChanged != null)
CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add));
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Keys"));
PropertyChanged(this, new PropertyChangedEventArgs("Values"));
}
}
public void Clear()
{
int keysCount = _dictionary.Keys.Count;
_dictionary.Clear();
if (keysCount == 0) return; //dont trigger changed event if there was no change.
if (CollectionChanged != null)
CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Keys"));
PropertyChanged(this, new PropertyChangedEventArgs("Values"));
}
}
public bool Contains(KeyValuePair<TKey, TValue> item)
{
return _dictionary.Contains(item);
}
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
_dictionary.CopyTo(array, arrayIndex);
}
public bool Remove(KeyValuePair<TKey, TValue> item)
{
bool remove = _dictionary.Remove(item);
if (!remove) return false; //don’t trigger change events if there was no change.
if (CollectionChanged != null)
CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove));
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Keys"));
PropertyChanged(this, new PropertyChangedEventArgs("Values"));
}
return true;
}
public int Count
{
get { return _dictionary.Count; }
}
public bool IsReadOnly
{
get { return _dictionary.IsReadOnly; }
}
public bool ContainsKey(TKey key)
{
return _dictionary.ContainsKey(key);
}
public void Add(TKey key, TValue value)
{
_dictionary.Add(key, value);
if (CollectionChanged != null)
CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add));
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Keys"));
PropertyChanged(this, new PropertyChangedEventArgs("Values"));
}
}
public bool Remove(TKey key)
{
bool remove = _dictionary.Remove(key);
if (!remove) return false;
if (CollectionChanged != null)
CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Remove));
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Keys"));
PropertyChanged(this, new PropertyChangedEventArgs("Values"));
}
return true;
}
public bool TryGetValue(TKey key, out TValue value)
{
return _dictionary.TryGetValue(key, out value);
}
public TValue this[TKey key]
{
get { return _dictionary[key]; }
set
{
bool changed = _dictionary[key].Equals(value);
if (!changed) return; //if there are no changes then we don’t need to update the value or trigger changed events.
_dictionary[key] = value;
if (CollectionChanged != null)
CollectionChanged(this, new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace));
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs("Keys"));
PropertyChanged(this, new PropertyChangedEventArgs("Values"));
}
}
}
public ICollection<TKey> Keys
{
get { return _dictionary.Keys; }
}
public ICollection<TValue> Values
{
get { return _dictionary.Values; }
}
}
