title: C# - Opening Settings.settings gets error about invalid xml in app.config (when configSource added)
body: <p>Following numerous examples, I added the following to my app.config file:</p>
  
  <p></p>
  
  <p>Everything seems to work when I run the application but when I try to open the Settings.settings file, I get the error:</p>
  
  <p>"An error occurred while reading the app.config file. The file might be corrupted or contain invalid XML."</p>
  
  <p>The Settings.settings file opens but I get a similar error message if I try to save it.</p>
  
  <p>App.config file:</p>
  
  <p>
  </p>
  
  <pre><code>&lt;configSections&gt;
      &lt;sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" &gt;
          &lt;section name="test.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" /&gt;
      &lt;/sectionGroup&gt;
  &lt;/configSections&gt;
  
  &lt;userSettings&gt;
      &lt;test.Properties.Settings&gt;
          &lt;setting name="server" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
          &lt;setting name="database" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
          &lt;setting name="g_language" serializeAs="String"&gt;
              &lt;value&gt;en-US&lt;/value&gt;
          &lt;/setting&gt;
          &lt;setting name="timeSchedule1" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
          &lt;setting name="timeSchedule2" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
          &lt;setting name="helpLocation" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
          &lt;setting name="SQLAuthType" serializeAs="String"&gt;
              &lt;value&gt;0&lt;/value&gt;
          &lt;/setting&gt;
          &lt;setting name="SQLLogin" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
          &lt;setting name="SQLPsw" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
          &lt;setting name="defaultTimeZone" serializeAs="String"&gt;
              &lt;value /&gt;
          &lt;/setting&gt;
      &lt;/test.Properties.Settings&gt;
  &lt;/userSettings&gt;
  
  &lt;connectionStrings configSource = "testConnect.config"/&gt;
  </code></pre>
  
  <p></p>