private void AddSuggestion(string str)
        {
            if (string.IsNullOrWhiteSpace(str))
            {
                return;
            }

            Buffer = StringOperation.ReplaceLastOccurrence(Buffer, StringOperation.LastWord(Buffer), str);
        }
        private void AsyncFindSuggestions()
        {
            if (Value != 100)
            {
                MessageBox.Show("Wait for the dictionary to load.");
                return;
            }

            FindSuggestionAsync.FindSuggestionAsyncDelegate findSuggestion = russianWordsSuggestionService.Find;
            try
            {
                asyncFindSuggestions = findSuggestion.BeginInvoke(StringOperation.LastWord(Buffer), Consts.CountSuggestions, CallbackFindSuggestions, null);
            }
            catch (ArgumentException)
            {
                // This block must be empty.
            }
        }