title: Unresolved external symbol while linking class files, Visual studio
body: <p>There are three files in a project: <br><br>
  <strong>HAT_array.h:</strong></p>
  <pre><code>#pragma once
  
  class HAT_array {
  public:
      HAT_array();
  };
  </code></pre>
  <p><strong>HAT_array.cpp:</strong></p>
  <pre><code>#include &quot;HAT_array.h&quot;
  
  inline HAT_array::HAT_array() {
      return;
  }
  </code></pre>
  <p><strong>test.cpp:</strong></p>
  <pre><code>#include &quot;HAT_array.h&quot;
  
  int main(void) {
      HAT_array HAT;
  }
  </code></pre>
  <p>While building the solution I receive an unresolved external symbol error:</p>
  <pre><code>1&gt;------ Build started: Project: HashedArrayTree, Configuration: Release Win32 ------
  1&gt;HAT_array.cpp
  1&gt;test.cpp
  1&gt;test.obj : error LNK2001: unresolved external symbol &quot;public: __thiscall HAT_array::HAT_array(void)&quot; (??0HAT_array@@QAE@XZ)
  1&gt;C:\Users\myros\Desktop\HashedArrayTree\Release\HashedArrayTree.exe : fatal error LNK1120: 1 unresolved externals
  1&gt;Done building project &quot;HashedArrayTree.vcxproj&quot; -- FAILED.
  ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
  </code></pre>