Find dictionary key by value

IDictionaryExtensions.cs

 public static class IDictionaryExtensions
    {
        /// <summary>
        /// Get key by value from dictionary
        /// </summary>
        /// <remarks>
        /// Thanks for shemesh's neat solution
        /// http://shemesh.wordpress.com/2010/01/22/c-dictionary-get-key-from-value/
        /// </remarks>
        public static TKey FindKeyByValue<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TValue value)
        {
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");

            foreach (KeyValuePair<TKey, TValue> pair in dictionary)
                if (value.Equals(pair.Value)) return pair.Key;

            throw new Exception("the value is not found in the dictionary");
        }
        /// <summary>
        /// Get key by value from dictionary
        /// </summary>
        /// <remarks>
        /// Extend the FindKeyByValue implementation and provide similar pattern to Dictionary TryGetValue method.
        /// </remarks>
        public static bool TryFindKeyByValue<TKey, TValue>(this IDictionary<TKey, TValue> dictionary, TValue value, out TKey key)
        {
            if (dictionary == null)
                throw new ArgumentNullException("dictionary");

            key = default(TKey);

            foreach (KeyValuePair<TKey, TValue> pair in dictionary)
            {
                if (value.Equals(pair.Value))
                {
                    key = pair.Key;
                    return true;
                }
            }
            return false;  
        }
    }