Why else statement for function userexiststoday not work and how to solve it

I work in c# windows form vs 2015 selecting data from excel
problem i face it
supose i have in excel file
user id dateprint
1001 22/02/2017

if try add this user 1001 again with date 23/02/2017
it must give me message this user found before
but this is not happen and this is actually my problem
my code

bool c = QRC.UserExists(textBox1.Text);  
  
bool b = UserExistsToday();  
  
if (c == true)  
  
{  
  
if (b == true)  
  
{  
  
  
label8.Text = "User added today";  
  
  
  
}  
  
  
else  
  
{  
  
  
label8.Text = "User added before";  
  
  
}