IDictionary<,>::GetValue

public static class DictionaryExtensions
{
  [DebuggerHidden]
  public static TValue GetValue<TKey, TValue>(this IDictionary<TKey, TValue> source, TKey key) {
    if(source == null) {
      throw new ArgumentNullException("source");
    }//if

    TValue value;
    if(!source.TryGetValue(key, out value)) {
      const string Format = "Key \"{0}\" does not found in a dictionary.";
      var message = String.Format(Format, key);
      throw new KeyNotFoundException(message);
    }//if

    return value;
  }

  // …
}