Internet Magic (Proxy Server) Windows Application

using System;
using System.Collections.Generic;
using System.Text;
using System.Collections;
using System.Collections.Specialized;
using System.Windows.Forms;
namespace internet_magic
{
    public class ip_mon_status
    {
        /// <summary>
        /// Constuct Class. 
        /// </summary>
        public ip_mon_status() { }
        ///<summary>Adds an item to the list.</summary>
        ///<param name="sts">The IP address to add.</param>
        ///<param name="tmlm">The corresponding time limit to add.</param>
        ///<exception cref="ArgumentNullException">Either feild is null.</exception>
        public void AddItem(string sts)
        {
            if (sts == null)
                throw new ArgumentNullException();
            Addst(sts);
        }
        ///<summary>Adds an item to the list.</summary>
        ///<param name="sts">The IP address to add.</param>
        ///<param name="tmlm">The corresponding time limit to add.</param>
        ///<exception cref="ArgumentNullException">Either feild is null.</exception>
        public void Addst(string sts)
        {
            if (Listing.ContainsKey(sts))
            {
                throw new ArgumentNullException();
            }
            else
            {
                Listing.Add(sts, null);
            }
        }
        ///<summary>Remove an item from the list.</summary>
        ///<param name="sts">The IP address to remove.</param>
        ///<exception cref="ArgumentNullException">sts feild is null.</exception>
        public void RemoveItem(string sts)
        {
            if (sts == null)
                throw new ArgumentNullException();
            Listing.Remove(sts);
        }
        ///<summary>Checks whether a IP address/Time limit is present in the collection or not.</summary>
        ///<param name="sts">The Corresponding IP address to search for.</param>
        ///<returns>True when the IP address is present in the collection, false otherwise.</returns>
        public bool IsItemPresent(string sts)
        {
            return IsstsPresent(sts);
        }
        ///<summary>Checks whether a IP address is present in the collection or not.</summary>
        ///<param name="sts">The IP address to search for.</param>
        ///<returns>True when the IP address is present in the collection, false otherwise.</returns>
        public bool IsstsPresent(string sts)
        {

            return Listing.ContainsKey(sts);
        }
       
        ///<summary>Gets an array with all the keys in the authentication list.</summary>
        ///<value>An array of strings containing all the keys in the authentication list.</value>
        public string[] Keys
        {
            get
            {
                ICollection keys = Listing.Keys;
                string[] ret = new string[keys.Count];
                keys.CopyTo(ret, 0);
                return ret;
            }
        }
        
        ///<summary>Gets an array with all the hashes in the authentication list.</summary>
        ///<value>An array of strings containing all the hashes in the authentication list.</value>
        protected StringDictionary Listing
        {
            get
            {
                return m_Listing;
            }
        }
        ///<summary>Clears the web list.</summary>
        public void Clear()
        {
            Listing.Clear();
        }
        // private variables
        /// <summary>Holds the value of the Listing property.</summary>
        private StringDictionary m_Listing = new StringDictionary();
    }
}