title: Visual Studio - External assembly does not update in a .Net 5.0 project
body: <p>I'm adding <code>NUnit</code> project <code>TestAutoNeatSoftware</code> in legacy Visual Studio solution <code>NeatSolution</code>, that already has <code>NeatLegacyProject</code> and <code>NeatSlowlyPortingClassLibrary</code>.</p>
  <p><code>NeatLegacyProject</code> and <code>NeatClassLibraryInProgress</code> use .Net Framework 4.8, but I'm aiming to port the whole to .Net 5.0, so <code>TestAutoNeatSoftware</code> uses .Net 5.0.</p>
  <p>All three projects use a class library we're developing in another solution, <code>GeneralPurposeLibrary</code>.</p>
  <p>When I first added <code>GeneralPurposeLibrary</code> as an assembly to <code>TestAutoNeatSoftware</code>, all was going well; the classes, properties and methods were readily usable and everything built smoothly.</p>
  <p>Then, I added interfaces to <code>GeneralPurposeLibrary</code> for mocks in <code>TestAutoNeatSoftware</code>; <code>GeneralPurposeLibrary</code> duly built.</p>
  <p>When I use such an interface in <code>NeatClassLibraryInProgress</code>, the build goes fine.</p>
  <p>However, when I try the same in <code>TestAutoNeatSoftware</code>, it doesn't seem to know that <code>GeneralPurposeLibrary</code> has been modified.</p>
  <p>I've tried the following:</p>
  <ul>
  <li>I've checked the access path for <code>GeneralPurposeLibrary</code> in all three projects: it's the same (except the one in <code>TestAutoNeatSoftware</code> has some letters in uppercase, but a <code>dir</code> command shows that it's actually more correct than the other two).</li>
  <li>I've looked up the GeneralPurposeLibrary.DLL file in Windows Explorer: its last modification date is the one I'd expect.</li>
  <li>I've right-clicked <code>GeneralPurposeLibrary</code> in Solution Explorer to open it in the Object browser: it shows the new classes, properties, and methods as it should.</li>
  <li>I've tried setting <code>GeneralPurposeLibrary</code>' properties consistently with those it has in the two other projects (they don't look exactly the same, but still), to no avail. For reference, the differences from default values were:
  <ul>
  <li>Local copy: Yes</li>
  <li>Embed interop types: No</li>
  <li>Specific version: No</li>
  </ul>
  </li>
  <li>Cleaning the solution does not affect the situation.</li>
  <li>If I restart Visual Studio, <code>TestAutoNeatSoftware</code> recognizes the new classes, properties and methods. Same if I remove/add <code>GeneralPurposeLibrary</code>.</li>
  </ul>
  <p>What can I do to make it better?</p>
  <p>(Aside: the properties' names are translated back from VS's French version, with help from Web searches, but I'd be grateful for a reference on assembly properties because I can't seem to find one.)</p>