c# - How to check where in your text file you found a string -

edit: fixed :) thanks!

i'm trying make login code , i'm having bit of trouble @ login function. need check line username located in, within text file. possible? if not there way around this?

edit: added code

using system; using system.collections.generic; using system.linq; using system.text;  namespace consoleapplication1 { class program {      static void main(string[] args)     {         int loginattempt = 0;          using (system.io.streamwriter file = new system.io.streamwriter("c:\\users\\public\\usernames.txt", true))         {             file.writeline();         }          int usertype = 0;         string retrievedusername = string.empty;          using (system.io.streamreader fileusername = new system.io.streamreader("c:\\users\\public\\usernames.txt"))         {             retrievedusername = fileusername.readtoend();         }            console.foregroundcolor = consolecolor.magenta;             console.writeline("please note prototype, passwords not hashed/encrypted ^_^. report bugs / flaws andrew.yu6@hotmail.com, if spam high 5 in face chair");             console.foregroundcolor = consolecolor.green;          console.writeline("welcome medata service! ver. 0.01 beta, made mechron");                 {             console.writeline("please enter login below or type register register new account on device");             string loginusername = console.readline();             if (loginusername == "login")             {                  console.writeline("type in username");                 string loginuser = console.readline();              }             else             {                 if (loginusername == "register")                 {                     int registerattempt = 0;                      console.writeline("choose username!");                     string registerusername = console.readline();                      bool containuser = system.io.file.readalllines("c:\\users\\public\\usernames.txt").contains(registerusername);                     if (containuser == true) { console.writeline("error, username exists! please try again!"); } else { registerattempt = 1; }                       if( registerattempt == 1 )                     {                     using (system.io.streamwriter files = new system.io.streamwriter("c:\\users\\public\\usernames.txt", true))                     {                         files.writeline(registerusername);                     }                     }                     if (registerattempt == 1)                     {                         console.writeline("now choose password!");                         string loginpass = console.readline();                         using (system.io.streamwriter files = new system.io.streamwriter("c:\\users\\public\\passwords.txt", true))                         {                             files.writeline(loginpass);                         }                         console.writeline("good! returned start screen! try login there!");                     }                 }                 else                 {                     console.writeline("error, command not recognized. try again");                 }               }         } while ( loginattempt == 0 ); 

try this:

if(loginusername == "login") {   console.writeline("type in username");   string loginuser = console.readline();   int linecount=1;   foreach(var line in file.readlines("loginfile.txt"))   {     if(line.contains(loginuser))     {        console.writeline("username found in line no = "+ linecount);        break;     }        linecount++;   } }