title: Problem Creating dll library file from various methods in C#?
body: <p><a href="https://i.stack.imgur.com/4rfNH.png" rel="nofollow noreferrer">sereenshot of my project</a></p>
  <ol>
  <li>I have a problem creating dll file.</li>
  <li>Errors of the problems are shown in picture.</li>
  <li>Anyone who knows the solution of the problems, help me please.</li>
  </ol>