If statement running both conditions, even though its IMPOSSIBLE to run the second condition if the first is met c# -

i have code, logging in software i'm writing, code checks username , password against file containing username , hashed passwords, however, if input other login stored on first line in file, both parts of if statement run, though impossible 'else' run if first condition met.

i can't seem find issues code, , of course, if login details correct, logs user in, though gives error saying cannot log in.

code:

system.io.streamreader file = new system.io.streamreader("userdata.txt"); string fileline; string line; while ((line = file.readline()) !=null) {     fileline = line;     system.diagnostics.debug.writeline(fileline);     string len = fileline.length.tostring();     string usr = fileline.substring(0, 20);     string hash = fileline.substring(20, 32);     if (usr.contains(usernameipt.text) && hash == password)     {         globalvar.usernameentered = usernameipt.text;         showuserpanel();         break;     }     else     {         messagebox.show("error, password or username incorrect. \r\n\r\nyou may not have account set use software, please contact system administartor assistance.", "login error");     } } 

let me explain code in pseudo code

lets pretend file contains names (to make life shorter) lets has

jon kate alison fred bill 

• so code says give me name, type in pete

• your code opens file , reads jon , goes "error"

• reads kate goes "error"

• reads alison goes "error"

  ...

so

you need change code slightly

• pick flag call "found" , set false

• if pick kate time,

• reads jon - nothing

• reads kate - sets found , breaks

• if found ok - else "error"

if picked pete end of file, found false, , once "error"