title: Could not resolve this reference error
body: <p>I have been writing a program and within the program I had to zip some files, so I used a addon called Ionic.Zip.</p>
  
  <p>When I run my program its perfectly fine with no errors, but now when I try to build my program as i have finished writing it I get the following error.</p>
  
  <pre><code>Code:
  Warning 1   Could not resolve this reference. Could not locate the assembly "Ionic.Zip". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors.
  and the same error for each form where I use the code to zip the files.
  </code></pre>
  
  <p>Any ideas what would cause this?</p>
  
  <p><img src="https://i.stack.imgur.com/X6iir.png" alt="enter image description here"></p>