.net - Read All Lines in a Text File and Add Them C# -

i've been working on problem while , i'm little stuck. have text file need loop through , read lines of, add of substrings 1 final number. problem is, have reading correctly , producing number first line in file only. i'm not sure whether use 'while' or 'for each'. here code have:

    string filepath = configurationsettings.appsettings["benefitsfile"];     streamreader reader = null;     filestream fs = null;     try     {         //read file , estimated return.         fs = new filestream(filepath, filemode.open, fileaccess.read, fileshare.readwrite);         reader = new streamreader(fs);         string line = reader.readline();         int soldtodate = convert.toint32(convert.todouble(line.substring(10, 15)));         int currentreturn = convert.toint32(soldtodate * .225);          //update return amount         updatecurrentreturn(currentreturn); 

any suggestions appreciated.

you use while loop so, reading in each line , checking see hasn't returned null

    string filepath = configurationsettings.appsettings["benefitsfile"];     streamreader reader = null;     filestream fs = null;     try     {         //read file , estimated return.         fs = new filestream(filepath, filemode.open, fileaccess.read, fileshare.readwrite);         reader = new streamreader(fs);          string line;         int currentreturn = 0;         while ((line = reader.readline()) != null){             int soldtodate = convert.toint32(convert.todouble(line.substring(10, 15)));             currentreturn += convert.toint32(soldtodate * .225);         }          //update return amount         updatecurrentreturn(currentreturn);      }     catch (ioexception e){      // handle exception and/or rethrow     }