string s = txtReviewStartDate.Text.Trim();
string[] words = s.Split(' ');
int month = DateTime.ParseExact(words[0].ToString(), "MMMM", System.Globalization.CultureInfo.InvariantCulture).Month;
hdnFromMonth.Value = month.ToString();
hdnFromYear.Value = words[1].ToString();
I tried like this , thanks eveyone for suggesting for this question . I solved my query with better way