C#: Observable Dictionary

C# WPF – An Observable String Dictionary class, which can be useful for storing and binding values as (key, value) pair

	// The orginal class was obtained from official site, then I made some desirable changes such as `UpdateOrAdd`,
	// which I think usefull for others
	//
	using System;
	using System.Collections;
	using System.Collections.Generic;
	using System.ComponentModel;
	namespace mynamespace
	{
	class ObservableDictionary : IDictionary<string, string>, INotifyPropertyChanged
	{
	//------------------------------------------------------
	//
	// Constructors
	//
	//------------------------------------------------------
	#region Constructors
	/// <summary>
	/// Creates a ContentLocatorPart with the specified type name and namespace.
	/// </summary>
	public ObservableDictionary()
	{
	_nameValues = new Dictionary<string, string>();
	}
	#endregion Constructors
	//------------------------------------------------------
	//
	// Public Methods
	//
	//------------------------------------------------------
	#region Public Methods
	/// <summary>
	/// Adds a key/value pair to the ContentLocatorPart. If a value for the key already
	/// exists, the old value is overwritten by the new value.
	/// </summary>
	/// <param name="key">key</param>
	/// <param name="val">value</param>
	/// <exception cref="ArgumentNullException">key or val is null</exception>
	/// <exception cref="ArgumentException">a value for key is already present in the locator part</exception>
	public void Add(string key, string val)
	{
	if (key == null || val == null)
	{
	throw new ArgumentNullException(key == null ? "key" : "val");
	}
	_nameValues.Add(key, val);
	FireDictionaryChanged();
	}
	/// <summary>
	/// Removes all name/value pairs from the ContentLocatorPart.
	/// </summary>
	public void Clear()
	{
	int count = _nameValues.Count;
	if (count > 0)
	{
	_nameValues.Clear();
	// Only fire changed event if the dictionary actually changed
	FireDictionaryChanged();
	}
	}
	public void UpdateOrAdd(string key,string value)
	{
	if (ContainsKey(key) == false)
	{
	Add(key, value);
	}
	else
	{
	Remove(key);
	Add(key, value);
	}
	}
	/// <summary>
	/// Returns whether or not a value of the key exists in this ContentLocatorPart.
	/// </summary>
	/// <param name="key">the key to check for</param>
	/// <returns>true - yes, false - no</returns>
	public bool ContainsKey(string key)
	{
	return _nameValues.ContainsKey(key);
	}
	/// <summary>
	/// Removes the key and its value from the ContentLocatorPart.
	/// </summary>
	/// <param name="key">key to be removed</param>
	/// <returns>true - the key was found in the ContentLocatorPart, false o- it wasn't</returns>
	public bool Remove(string key)
	{
	bool exists = _nameValues.Remove(key);
	// Only fire changed event if the key was actually removed
	if (exists)
	{
	FireDictionaryChanged();
	}
	return exists;
	}
	/// <summary>
	/// Returns an enumerator for the key/value pairs in this ContentLocatorPart.
	/// </summary>
	/// <returns>an enumerator for the key/value pairs; never returns null</returns>
	IEnumerator IEnumerable.GetEnumerator()
	{
	return _nameValues.GetEnumerator();
	}
	/// <summary>
	/// Returns an enumerator forthe key/value pairs in this ContentLocatorPart.
	/// </summary>
	/// <returns>an enumerator for the key/value pairs; never returns null</returns>
	public IEnumerator<KeyValuePair<string, string>> GetEnumerator()
	{
	return ((IEnumerable<KeyValuePair<string, string>>)_nameValues).GetEnumerator();
	}
	/// <summary>
	///
	/// </summary>
	/// <param name="key"></param>
	/// <param name="value"></param>
	/// <returns></returns>
	/// <exception cref="ArgumentNullException">key is null</exception>
	public bool TryGetValue(string key, out string value)
	{
	if (key == null)
	throw new ArgumentNullException("key");
	return _nameValues.TryGetValue(key, out value);
	}
	/// <summary>
	///
	/// </summary>
	/// <param name="pair"></param>
	/// <exception cref="ArgumentNullException">pair is null</exception>
	void ICollection<KeyValuePair<string, string>>.Add(KeyValuePair<string, string> pair)
	{
	((ICollection<KeyValuePair<string, string>>)_nameValues).Add(pair);
	}
	/// <summary>
	///
	/// </summary>
	/// <param name="pair"></param>
	/// <returns></returns>
	/// <exception cref="ArgumentNullException">pair is null</exception>
	bool ICollection<KeyValuePair<string, string>>.Contains(KeyValuePair<string, string> pair)
	{
	return ((ICollection<KeyValuePair<string, string>>)_nameValues).Contains(pair);
	}
	/// <summary>
	///
	/// </summary>
	/// <param name="pair"></param>
	/// <returns></returns>
	/// <exception cref="ArgumentNullException">pair is null</exception>
	bool ICollection<KeyValuePair<string, string>>.Remove(KeyValuePair<string, string> pair)
	{
	return ((ICollection<KeyValuePair<string, string>>)_nameValues).Remove(pair);
	}
	/// <summary>
	///
	/// </summary>
	/// <param name="target"></param>
	/// <param name="startIndex"></param>
	/// <exception cref="ArgumentNullException">target is null</exception>
	/// <exception cref="ArgumentOutOfRangeException">startIndex is less than zero or greater than the lenght of target</exception>
	void ICollection<KeyValuePair<string, string>>.CopyTo(KeyValuePair<string, string>[] target, int startIndex)
	{
	if (target == null)
	throw new ArgumentNullException("target");
	if (startIndex < 0 || startIndex > target.Length)
	throw new ArgumentOutOfRangeException("startIndex");
	((ICollection<KeyValuePair<string, string>>)_nameValues).CopyTo(target, startIndex);
	}
	#endregion Public Methods
	//------------------------------------------------------
	//
	// Public Operators
	//
	//------------------------------------------------------
	//------------------------------------------------------
	//
	// Public Events
	//
	//------------------------------------------------------
	//------------------------------------------------------
	//
	// Public Properties
	//
	//------------------------------------------------------
	#region Public Properties
	/// <summary>
	/// The number of name/value pairs in this ContentLocatorPart.
	/// </summary>
	/// <value>count of name/value pairs</value>
	public int Count
	{
	get
	{
	return _nameValues.Count;
	}
	}
	/// <summary>
	/// Indexer provides lookup of values by key. Gets or sets the value
	/// in the ContentLocatorPart for the specified key. If the key does not exist
	/// in the ContentLocatorPart,
	/// </summary>
	/// <param name="key">key</param>
	/// <returns>the value stored in this locator part for key</returns>
	public string this[string key]
	{
	get
	{
	if (key == null)
	{
	throw new ArgumentNullException("key");
	}
	string value = null;
	_nameValues.TryGetValue(key, out value);
	return value;
	}
	set
	{
	if (key == null)
	{
	throw new ArgumentNullException("key");
	}
	if (value == null)
	{
	throw new ArgumentNullException("value");
	}
	string oldValue = null;
	_nameValues.TryGetValue(key, out oldValue);
	// If the new value is actually different, then we add it and fire
	// a change notification
	if ((oldValue == null) || (oldValue != value))
	{
	_nameValues[key] = value;
	FireDictionaryChanged();
	}
	}
	}
	/// <summary>
	///
	/// </summary>
	public bool IsReadOnly
	{
	get
	{
	return false;
	}
	}
	/// <summary>
	/// Returns a collection of all the keys in this ContentLocatorPart.
	/// </summary>
	/// <value>keys</value>
	public ICollection<string> Keys
	{
	get
	{
	return _nameValues.Keys;
	}
	}
	/// <summary>
	/// Returns a collection of all the values in this ContentLocatorPart.
	/// </summary>
	/// <value>values</value>
	public ICollection<string> Values
	{
	get
	{
	return _nameValues.Values;
	}
	}
	#endregion Public Properties
	//------------------------------------------------------
	//
	// Public Events
	//
	//------------------------------------------------------
	//------------------------------------------------------
	//
	// Internal Methods
	//
	//------------------------------------------------------
	//------------------------------------------------------
	//
	// Internal Operators
	//
	//------------------------------------------------------
	//------------------------------------------------------
	//
	// Internal Events
	//
	//------------------------------------------------------
	#region Public Events
	/// <summary>
	///
	/// </summary>
	public event PropertyChangedEventHandler PropertyChanged;
	#endregion Public Events
	//------------------------------------------------------
	//
	// Internal Properties
	//
	//------------------------------------------------------
	//------------------------------------------------------
	//
	// Private Methods
	//
	//------------------------------------------------------
	#region Private Methods
	/// <summary>
	/// Notify the owner this ContentLocatorPart has changed.
	/// </summary>
	private void FireDictionaryChanged()
	{
	if (PropertyChanged != null)
	{
	PropertyChanged(this, new PropertyChangedEventArgs(null));
	}
	}
	#endregion Private Methods
	//------------------------------------------------------
	//
	// Private Fields
	//
	//------------------------------------------------------
	#region Private Fields
	/// <summary>
	/// The internal data structure.
	/// </summary>
	private Dictionary<string, string> _nameValues;
	#endregion Private Fields
	}
	}

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