Error in c# while connecting to Directory Services

[pinga123]

I m trying to connect to my Active Directory and fetch the attribute of my AD.

Whenever i trying to execute the console application made in c# i get following error.
Please Help

The type or namespace name 'DirectoryServices' does not exist in the namespace 'System' (are you missing an assembly reference?)

My code is as follows.

using System;
using System.Collections.Generic;
using System.Text;
using System.DirectoryServices.ActiveDirectory;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            DirectoryEntryConfigurationSettings("LDAP://dc=abc,dc=com");
        }
        static void DirectoryEntryConfigurationSettings(string domainADsPath)
{
    // Bind to current domain

    DirectoryEntry entry = new DirectoryEntry(domainADsPath);
    DirectoryEntryConfiguration entryConfiguration = entry.Options;

    Console.WriteLine("Server: " + entryConfiguration.GetCurrentServerName());
    Console.WriteLine("Page Size: " + entryConfiguration.PageSize.ToString());
    Console.WriteLine("Password Encoding: " + 
        entryConfiguration.PasswordEncoding.ToString());
    Console.WriteLine("Password Port: " + 
        entryConfiguration.PasswordPort.ToString());
    Console.WriteLine("Referral: " + entryConfiguration.Referral.ToString());
    Console.WriteLine("Security Masks: " + 
        entryConfiguration.SecurityMasks.ToString());
    Console.WriteLine("Is Mutually Authenticated: " + 
        entryConfiguration.IsMutuallyAuthenticated().ToString());
    Console.WriteLine();
    Console.ReadLine();
}
    }
    
}

[pinga123]

Hi guys i Have resolved my problem by adding.
using System.Director yServices;
at first line.