How to view all user of a active directory group

public static DataSet GetUsersForGroup(string GroupName)
{
DataSet dsUser = new DataSet();
DirectoryEntry de = GetDirectoryObject();

//create instance fo the direcory searcher
DirectorySearcher deSearch = new DirectorySearcher();

//set the search filter
deSearch.SearchRoot =de;
//deSearch.PropertiesToLoad.Add("cn");
deSearch.Filter = "(&(objectClass=group)(cn=" + GroupName +"))";

//get the group result
SearchResult results= deSearch.FindOne();

//Create a new table object within the dataset
DataTable tbUser = dsUser.Tables.Add("Users");
tbUser.Columns.Add("UserName");
tbUser.Columns.Add("DisplayName");
tbUser.Columns.Add("EMailAddress");

//Create default row
DataRow rwDefaultUser = tbUser.NewRow();
rwDefaultUser ["UserName"]= "0";
rwDefaultUser ["DisplayName"]="(Not Specified)";
rwDefaultUser ["EMailAddress"]="(Not Specified)";
tbUser.Rows.Add(rwDefaultUser);

//if the group is valid, then continue, otherwise return a blank dataset
if(results !=null)
{
//create a link to the group object, so we can get the list of members
//within the group
DirectoryEntry deGroup= new DirectoryEntry(results.Path,ADAdminUser,ADAdminPassword,AuthenticationTypes.Secure);
//assign a property collection
System.DirectoryServices.PropertyCollection pcoll = deGroup.Properties;
int n = pcoll["member"].Count;

//if there are members fo the group, then get the details and assign to the table
for (int l = 0; l < n ; l++)
{
//create a link to the user object sot hat the FirstName, LastName and SUername can be gotten
DirectoryEntry deUser= new DirectoryEntry(ADFullPath + "/" +pcoll["member"][l].ToString(),ADAdminUser,ADAdminPassword,AuthenticationTypes.Secure);

//set a new empty row
DataRow rwUser = tbUser.NewRow();

//populate the column
rwUser["UserName"]= GetProperty(deUser,"cn");
rwUser["DisplayName"]= GetProperty(deUser,"givenName") + " " + GetProperty(deUser,"sn");
rwUser["EMailAddress"]= GetProperty(deUser,"mail");
//append the row to the table of the dataset
tbUser.Rows.Add(rwUser);

//close the directory entry object
deUser.Close();

}
de.Close();
deGroup.Close();
}

return dsUser;
}

How to Display Active Directory User details inculding Expiry Date

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.DirectoryServices;
using Microsoft.VisualBasic;

namespace AD
{
    class Program
    {
          
        static public void Main(string[] args)
        {
            string username = "testuser1";
            DirectoryEntry user = new DirectoryEntry("LDAP://CN=" + username + "," + " OU= Web Users,DC=CGSTAGE,DC=com", null, null, AuthenticationTypes.Secure);
           
            // GetInt64 is used to conver system._comObject to 64bit integer
            DateTime expires = DateTime.FromFileTime(GetInt64(user, "accountExpires"));
          
            Console.WriteLine(expires.ToString());

            Console.WriteLine("Display Name "+user.Properties["displayName"].Value.ToString());
            Console.WriteLine("First Name "+user.Properties["givenName"].Value.ToString());
            Console.WriteLine("Last Name "+user.Properties["sn"].Value.ToString());
            Console.WriteLine("Mail ID "+user.Properties["mail"].Value.ToString());


            Console.ReadKey();

        }

           
        static public Int64 GetInt64(DirectoryEntry entry, string attr)
        {           
            DirectorySearcher ds = new DirectorySearcher(
                entry,
                String.Format("({0}=*)", attr),
                new string[] { attr },
                SearchScope.Base
                );

            SearchResult sr = ds.FindOne();

            if (sr != null)
            {
                if (sr.Properties.Contains(attr))
                {
                    return (Int64)sr.Properties[attr][0];
                }
            }
            return -1;
        }

    }
}