/// <summary>
/// Not supported by <see cref="T:DesktopSprites.Collections.LazyDictionary`2"/>.
/// </summary>
/// <param name="item">The parameter is not used.</param>
/// <returns>The method does not return.</returns>
/// <exception cref="T:System.NotSupportedException">Thrown when the method is invoked.</exception>
bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item)
{
throw new NotSupportedException("Not supported by " + GetType().Name);
}
/// <summary>
/// Determines whether the <see cref="T:DesktopSprites.Collections.LazyDictionary`2"/> contains a specific value.
/// </summary>
/// <param name="item">The object to locate in the <see cref="T:DesktopSprites.Collections.LazyDictionary`2"/>.</param>
/// <returns>Returns true if item is found in the <see cref="T:DesktopSprites.Collections.LazyDictionary`2"/>; otherwise, false.
/// </returns>
/// <exception cref="T:System.ArgumentNullException"><paramref name="item"/> is null.</exception>
bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> item)
{
bool found = dictionary.TryGetValue(item.Key, out Lazy<TValue> lazy);
return found ? EqualityComparer<TValue>.Default.Equals(item.Value, lazy.Value) : false;
}