public class LinksCtrlDto
   {
      /// <summary>
      /// url link
      /// </summary>
      private string _url;

      /// <summary>
      /// name of link
      /// </summary>
      private string _name;

      /// <summary>
      /// description of string
      /// </summary>
      private string _description;

      /// <summary>
      /// constructor for LinksCtrlDto
      /// </summary>
      /// <param name="url"></param>
      /// <param name="name"></param>
      /// <param name="description"></param>
      public LinksCtrlDto( string url, string name, string description ) {

         //only if url si not null/empty, name is not null/empty, and description is not null/empty
         if ( string.IsNullOrEmpty( url ) )
            throw new ArgumentNullException( "url" );
         else
            this._url = url;

         if ( string.IsNullOrEmpty( name ) )
            throw new ArgumentNullException( "name" );
         else
            this._name = name;

         if ( string.IsNullOrEmpty( description ) )
            throw new ArgumentNullException( "description" );
         else
            this._description = description;
      }

      /// <summary>
      /// Url property as getter
      /// </summary>
      public string Url {
         get {
            if ( string.IsNullOrEmpty( Url ) )
               throw new ArgumentNullException( "Url" );
            else
               return this._url;
         }
      }

      /// <summary>
      /// Name property as getter
      /// </summary>
      public string Name {
         get {
            if ( string.IsNullOrEmpty( Name ) )
               throw new ArgumentNullException( "Name" );
            else
               return this._name;
         }
      }

      /// <summary>
      /// Description property as getter
      /// </summary>
      public string Description {
         get {
            if ( string.IsNullOrEmpty( Description ) )
               throw new ArgumentNullException( "Description" );
            else
               return this._description;
         }
      }
   }



   public class CategoriesCtrlDto
   {
      /// <summary>
      /// Name of category
      /// </summary>
      private string _name;

      /// <summary>
      /// List of links
      /// </summary>
      private List<LinksCtrlDto> _ListLink;

      /// <summary>
      /// constructor
      /// </summary>
      /// <param name="name"></param>
      /// <param name="Link"></param>
      public CategoriesCtrlDto( string name, List<LinksCtrlDto> Link) {
         if ( string.IsNullOrEmpty( name ) )
            throw new ArgumentNullException( "name" );
         else
            this._name = name;

         if ( _ListLink == null )
            throw new ArgumentNullException( "_ListLink" );
         else
            this._ListLink = Link;
         }

      /// <summary>
      /// add link in List
      /// </summary>
      /// <param name="url"></param>
      /// <param name="name"></param>
      /// <param name="description"></param>
      public List<LinksCtrlDto> AddLink( string url, string name ,string description ) {
         if ( string.IsNullOrEmpty( url ) )
            throw new ArgumentNullException( "AddLink TL Categories - url" );
         if ( string.IsNullOrEmpty( name ) )
            throw new ArgumentNullException( "Addlink TL Categories - name" );
         if ( string.IsNullOrEmpty( description ) )
            throw new ArgumentNullException( "Addlink TL Categories - description" );

         _ListLink.Add( new LinksCtrlDto( url, name, description ) );

         return _ListLink;
      }


      /// <summary>
      /// delete a link from list if URL name is matched
      /// </summary>
      /// <param name="url"></param>
      /// <param name="name"></param>
      /// <param name="description"></param>
      public void DeleteLink( string url ) {
         if ( string.IsNullOrEmpty( url ) )
            throw new ArgumentNullException( "deletelink TL url" );

         foreach ( LinksCtrlDto lk in _ListLink ) {
            if ( lk.Url == url ) {
               _ListLink.Remove( lk );
               break;
            }
         }
      }

      /// <summary>
      /// Verify that link already exists in specified category
      /// </summary>
      /// <param name="url"></param>
      /// <returns></returns>
      public bool LinkExists(string url){
         bool result = false;

         if ( string.IsNullOrEmpty( url ) )
            throw new ArgumentNullException( "LinkExists name TL Categories" );

         foreach ( LinksCtrlDto lk in Links ) {
            if ( lk.Url == url ) {
               result = true;
               break;
            }
         }

         return result;

      }


      /// <summary>
      /// Name property as getter
      /// </summary>
      public string Name {
         get {
            return this._name;
         }
      }



      /// <summary>
      /// List property as getter
      /// </summary>
      public ReadOnlyCollection<LinksCtrlDto> Links {
         get {
            return this._ListLink.AsReadOnly();
         }
      }
   }