why do i keep getting errors in c$++$ code when using getline?

#include

#include

$/////////////////$ Task $1$: $///////////////////////////////$

#include $//$ fstream library

#include $//$sstream library for istringstream function

#include

using namespace std;

$//$ Function prototype

bool userAuthentication$()$;

void getCredentials$($const string prompt, string &data$)$;

int main$()$

$\{$

$//$ Check if the user is authorized

$$ if $($userAuthentication$())$

$\{$

$$ cout $<<$ "User is authenticated." $<<$ endl;

$\}$

$$ else

$\{$

$$ cout $<<$ "Authentication failed." $<<$ endl;

$\}$

$$ return $0$;

$\}$

$/*$

$*$ Input: None

$*$ Purpose: This function authenticates a user

$*$ Output: true or false $($bool$)$

$*/$

$//$ Task$2$: $$define the function

bool userAuthentication$()$

$\{$

$/////////////////$ Task $2$a: $///////////////////////////////$

$$ string line;

$$ string tempUserName;

$$ string tempPassword;

$$ string userName; $//$declare userName

$$ string password; $//$declare pw

$/////////////////$ Task $2$b: $///////////////////////////////$

getCredentials$("$What is the UserName:", userName$)$; $//$call function userName

getCredentials$("$What is your password:", password$)$; $//$call funtion password

$//$ Task #$3///$

$/////////////////$ Task $3$a: $///////////////////////////////$

$$ ifstream adminFile $("$credentials$.$txt$")$;

$/////////////////$ Task $3$b: $///////////////////////////////$

adminFile.open$("$credentials$.$txt$")$;

$//$ Check if the adminFile opened successfully.

$$ if $(!$adminFile.is$\_$open$())$

$\{$

$$ cout $<<$ "System error in authentication. $"<<$ endl;

$$ return false;

$\}$

$$ else

$\{$

$/////////////////$ Task $3$c: $///////////////////////////////)$

$$ while $($getLine$($adminFile$,$ line$))\{$

$$ cout $<<"**$Showing the content of the file $**."<$