/// <summary>
/// Gets a value from the dictionary with given key. Returns default value if can not find.
/// </summary>
/// <param name="dictionary">Dictionary to check and get</param>
/// <param name="key">Key to find the value</param>
/// <param name="factory">A factory method used to create the value if not found in the dictionary</param>
/// <typeparam name="TKey">Type of the key</typeparam>
/// <typeparam name="TValue">Type of the value</typeparam>
/// <returns>Value if found, default if can not found.</returns>
public static TValue GetOrAdd <TKey, TValue>(this IDictionary <TKey, TValue> dictionary, TKey key, Func <TValue> factory)
{
return(dictionary.GetOrAdd(key, k => factory()));
}