title: app.config error "corrupted or contain invalid XML"?
body: <p>After many tries of trying to fix this error message, I still cannot manage to fix it and it only appears when I try to add a property to Settings.settings:</p>
  
  <blockquote>
    <p>An error occurred when saving values to the app.config file. The file might be corrupted or contain invalid XML.</p>
  </blockquote>
  
  <p>Yes, I have looked for a fix online already but I haven't found a solution because I haven't even messed with my app.config file whatsoever. Here is my app.config file code:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  &lt;configuration&gt;
      &lt;startup&gt; 
          &lt;supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" /&gt;
      &lt;/startup&gt;
  &lt;/configuration&gt;
  </code></pre>