How to add reference to assembly in vs2012
<p>I need help on how to correctly add assembly in C# code.</p>

<p>I start a blank project and trying to run the simple code below. but has referencing  errors.
I know by default system.dll is included under the references folder.</p>

<p>so why is it still complain that "'System.Configuration is not been referenced"? 
Am I missing some manual steps? If so how do I do it?</p>

<pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Configuration;

namespace ConsoleApplication2
{
    class Program
    {
        static void Main(string[] args)
        {
            HttpWebRequestElement ae = new HttpWebRequestElement();
            ae.UseUnsafeHeaderParsing = false;
        }
    }
}
</code></pre>

<p><strong>The type 'System.Configuration.ConfigurationElement' is defined in an assembly that is not referenced. 
You must add a reference to assembly 'System.Configuration, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.</strong></p>

<p>Thanks for helping</p>
