尝试寻找内部异常的更多详细信息。它帮助我，当我有同样的烦恼。

Try looking the Inner Exception for more detailed information. It helped me out when I had this same trouble.

此外，检查格式是否为您正在使用您的项目.NET框架是正确的。如果您使用的框架4.5它看起来应该像下面这样：

Also, check if the format is correct for the .net Framework you are using on your project. If you're using the framework 4.5 it should look like the one below:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>
  <appSettings>
    <add key="RemoteDirectory" value="Some Text Here" />
  </appSettings>
</configuration>