strings in .NET are immutable!
string.Replace()
does
not modify the string in place. It returns a new string with the replacement(s) performed.
Try:
body_confirmation = body_confirmation.Replace("##comfirmStates##", "You have submitted the following booking:");
body_confirmation = body_confirmation.Replace("##Customer##", "zhangdongling@hotmail.com");
body_confirmation = body_confirmation.Replace("##Job No#", "Job No");
body_confirmation = body_confirmation.Replace("##Reference##", "Reference");
body_confirmation = body_confirmation.Replace("##PassengerName##", "Sandy");
body_confirmation = body_confirmation.Replace("##PassengerNumber##", "Sandy passenger Number");
body_confirmation = body_confirmation.Replace("##Contact Phone##", "contact phone");
OR
body_confirmation = body_confirmation.Replace("##comfirmStates##", "You have submitted the following booking:")
.Replace("##Customer##", "zhangdongling@hotmail.com")
.Replace("##Job No#", "Job No")
.Replace("##Reference##", "Reference")
.Replace("##PassengerName##", "Sandy")
.Replace("##PassengerNumber##", "Sandy passenger Number")
.Replace("##Contact Phone##", "contact phone");