error creating the web proxy specified in the 'system.net/defaultproxy' configuration section

I had this same problem today and found a solution for it. In my case, the problem occurred because I was using a network disk for storing my project. When run from this network disk, this problem occurred. I moved the project to my local hard drive and it was gone. I am guessing this has something to do with security, as Windows considers the network drive less secure than my hard disk.

Try to add the below lines to your app.config or web.config and your application might work.

<system.net>
    <defaultProxy enabled="false" useDefaultCredentials="false">
    </defaultProxy>
  </system.net>