How to add reference to assembly in vs2012

Question

I need help on how to correctly add assembly in C# code.

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.

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?

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;
        }
    }
}

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'.

Thanks for helping

Solution

Right click on project references and add reference to System.Configuration

Comments

[Admin]

Thank you, It worked! yes, I should have read the error message more carefully. I was confused because I saw it somewhere that UseUnsafeHeaderParsing is from system.net.configuration so I thought I have to find an assembly from system.net, but it appeared to be system.configuration.

[Karan Kalra]

Thanks a lot! You are a savior.