public ICollection <ISentence> ReplaceWordWithString(string str, int number, Parsing parser, int length) { ICollection <ISentence> newCollection = DuplicateCollection(); ISentence sentence = newCollection.ElementAt(number); foreach (var component in sentence.ComponentsCollection) { if (component.GetType() == typeof(Word)) { if ((component as Word).Component.Length == length) { (component as Word).Component = str; } } } string buffer = null; foreach (var component in sentence.ComponentsCollection) { buffer += component.Component; } sentence.ComponentsCollection = parser.GetSentenceComponent(buffer); return(newCollection); }