The fastest way to check number in txt file
<p>H iguys. I have a loop which parse users id's and adds tham to txt file.
What's the best way than to check if this txt has this id skip it ( while next parsing ).
The size of txt rises from 5-..... mb</p>

<p>I tried to add ids to List, but when the size of file if bigger than 5mb the app begins hanging</p>
