title: ConfigurationManager.ConnectionStrings is picking up an unexpected value
body: <p>Environment: Visual Studio 2017<br>
  .Net Framework 4.6.1</p>
  
  <p><strong>Update</strong>
  I apologize, I failed to mention that I was using a UnitTesting project to do an integration test. So it looks like I need the app.config in there as well, correct?</p>
  
  <p>I am getting an unexpected value for connection string when using the following:</p>
  
  <p><strong>C# .Net Framework Library</strong></p>
  
  <pre><code>string connStr = ConfigurationManager.ConnectionStrings["test123"].ConnectionString;
  </code></pre>
  
  <p><strong>app.config</strong></p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  &lt;configuration&gt;
    &lt;connectionStrings&gt;
      &lt;add name="test123" connectionString="Data Source=.;Initial Catalog=AbcCompanyDb;Integrated Security=True;"/&gt;
    &lt;/connectionStrings&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>I did a search on Entire Solution and can't find any reference to </p>
  
  <blockquote>
    <p>.\sqlexpress</p>
  </blockquote>
  
  <p><strong>Value of connection string during debug</strong></p>
  
  <pre><code>{data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true}
  </code></pre>