public sealed class ApplicationAssociationManager : IAssociationPersistence
{
   const string nextAssocCleanup = "OpenID_NextAssocCleanup";
   const string associations = "OpenID_Associations";

   private DateTime NextCleanup
   {
       get 
       {
           if (HttpContext.Current.Application[nextAssocCleanup] == null) { return DateTime.MaxValue; }
           return (DateTime)HttpContext.Current.Application[nextAssocCleanup]; 
       }
       set { HttpContext.Current.Application[nextAssocCleanup] = value; }
   }

   private DataTable Associations
   {
       get
       {
           if (HttpContext.Current.Application[associations] == null)
           {
               Init();
           }
           return (DataTable)HttpContext.Current.Application[associations];
       }
       set
       {
           if (HttpContext.Current.Application[associations] == null)
           {
               Init();
           }
           HttpContext.Current.Application[associations] = value;
       }
   }

   public void Init()
   {
       DataTable dt = new DataTable();
       dt.Columns.Add("protocol", typeof(ProtocolVersion));
       dt.Columns.Add("server", typeof(string));
       dt.Columns.Add("handle", typeof(string));
       dt.Columns.Add("assoc_type", typeof(string));
       dt.Columns.Add("session_type", typeof(string));
       dt.Columns.Add("secret", typeof(byte[]));
       dt.Columns.Add("expiration", typeof(DateTime));
       dt.AcceptChanges();

       HttpContext.Current.Application[associations] = dt;
   }

   public void Remove(Association assoc)
   {
       DataRow[] rows = Associations.Select("handle = '" + assoc.Handle + "'");
       foreach (DataRow dr in rows) 
       {
           Associations.Rows.Remove(dr);
       }
       Associations.AcceptChanges();
   }

   public void Add(Association association)
   {
       // Check for existing association
       DataRow[] result = Associations.Select("server = '" + association.Server + "'");
       if (result.Length > 0)
       {
           for (int i = 0; i < result.Length; i++)
           {
               Associations.Rows.Remove(result[i]);
           }
       }

       // Add new row
       DataRow dr = Associations.NewRow();
       dr["protocol"] = association.ProtocolVersion;
       dr["server"] = association.Server;
       dr["handle"] = association.Handle;
       dr["assoc_type"] = association.AssociationType;
       dr["session_type"] = association.SessionType;
       dr["secret"] = association.Secret;
       dr["expiration"] = association.Expiration;
       Associations.Rows.Add(dr);
       Associations.AcceptChanges();
   }

   private Association ToAssociation(DataRow dr)
   {
       Association ar = new Association();
       ar.ProtocolVersion = (ProtocolVersion)dr["protocol"];
       ar.Server = (string)dr["server"];
       ar.Handle = (string)dr["handle"];
       ar.AssociationType = (string)dr["assoc_type"];
       ar.SessionType = (string)dr["session_type"];
       ar.Secret = (byte[])dr["secret"];
       ar.Expiration = (DateTime)dr["expiration"];
       return ar;
   }

   public Association FindByHandle(string handle)
   {
       DataRow[] result = Associations.Select("handle = '" + handle + "'");
       if (result.Length > 0)
       {
           return ToAssociation(result[0]);
       }
       return null;
   }

   public Association FindByServer(string server)
   {
       DataRow[] result = Associations.Select("server = '" + server + "'");
       if (result.Length > 0)
       {
           return ToAssociation(result[0]);
       }
       return null;
   }

   public void Cleanup()
   {
       if (NextCleanup == null || NextCleanup < DateTime.UtcNow)
       {
           foreach (DataRow dr in Associations.Rows)
           {
               if ((DateTime)dr["expiration"] < DateTime.UtcNow)
               {
                   dr.Delete();
               }
           }
           Associations.AcceptChanges();
           NextCleanup = DateTime.UtcNow.AddMinutes(10);
       }
   }
}