using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.Configuration;
using System.Web;
using System.Web.Configuration;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Web.UI.Adapters;
using System.Security.Permissions;


/// <summary>
/// Summary description for SqlPageStatePersister
/// </summary>

namespace AspItalia
{
    public class SqlStatePersister : PageStatePersister
    {
        #region query
        public const string saveQuery =
    @"
IF @GUID IS  NULL
  BEGIN
  SET @GUID = NEWID()
  INSERT INTO SqlViewState
                        (ID,Value, FirstAccess, LastAccess)
  VALUES     (@GUID ,@VIEWSTATE, GETDATE(), GETDATE())
  END
ELSE
  BEGIN
  UPDATE    SqlViewState
  SET              Value = @VIEWSTATE, LastAccess = GETDATE()
  WHERE     (ID = @GUID)
  END";

        public const string ReadQuery = "SELECT Value FROM SqlViewState WHERE ID = @GUID";
        #endregion

        public SqlStatePersister(Page page): base(page){ }

        public override void Load()
        {
            //recupero il guid
            string s = this.Page.Request.Form["__HiddenGuid"];
            //se esiste
            if (!string.IsNullOrEmpty(s))
            {
                //creo un nuovo guid
                Guid id = new Guid(s);
                //recupero il formatter
                IStateFormatter formatter = this.StateFormatter;
                //recupero la connessione
                SqlConnection connection = new SqlConnection(WebConfigurationManager.ConnectionStrings[0].ConnectionString);
                try
                {
                    //inizializzo una nuova istanza di SqlCommand
                    SqlCommand command = new SqlCommand(ReadQuery, connection);
                    //inizializzo il parametro @GUID e lo aggiungo al comando
                    SqlParameter guidParameter = new SqlParameter("@GUID", SqlDbType.UniqueIdentifier);
                    guidParameter.Value = id == Guid.Empty ? SqlGuid.Null : id;
                    guidParameter.Direction = ParameterDirection.Input;
                    command.Parameters.Add(guidParameter);
                    //apro la connessione
                    connection.Open();
                    //recupero il viewstate
                    object ob = command.ExecuteScalar();
                    //chiudo la connessione
                    connection.Close();
                    //deserializzo lo stao dei controlli
                    Pair pair = (Pair)formatter.Deserialize((string)ob);
                    //imposto il ViewState
                    ViewState = pair.First;
                    //imposto il ControlState
                    ControlState = pair.Second;
                }
                finally 
                {
                    if (connection.State != ConnectionState.Closed)
                    {
                        connection.Close();
                    }
                }
            }
        }

        public override void Save()
        {
            //se il ViewState o il ControlState non sono nulli
            if (this.ViewState != null || this.ControlState != null)
            {
                Pair statePair = new Pair(ViewState, ControlState);
                //recupero il guid precedentemente salvato dal campo nascosto
                string s = this.Page.Request.Form["__HiddenGuid"];
                Guid guid;
                try
                {
                    //se è stato salvato 
                    if (!string.IsNullOrEmpty(s))
                    {
                        //creoil guid
                        guid = new Guid(s);
                    }
                    else
                    {
                        guid = Guid.Empty;
                    }
                }
                catch
                {
                    guid = Guid.Empty;
                }
                //salvo lo stato dei controlli sul DataBase
                SaveOrUpdateViewStateToSqlServer(this.StateFormatter.Serialize(statePair), ref guid);
                //instanzio una nuvo campo hidden per contenere il guid
                HiddenField hiddenGuid = new HiddenField();
                //li assegno un id
                hiddenGuid.ID = "__HiddenGuid";
                //salvo il guid
                hiddenGuid.Value = guid.ToString();
                //aggiungo HiddenField alla collezione del controllo HtmlForm
                this.Page.Controls[3].Controls.Add(hiddenGuid);
            }
        }

        private void SaveOrUpdateViewStateToSqlServer(string stringToSave, ref Guid id)
        {
            //inizializzo una nuova istanza di SqlConnection con la stringa di connessione
            SqlConnection connection = new SqlConnection(WebConfigurationManager.ConnectionStrings[0].ConnectionString);
            try
            {
                //inizializzo SqlCommand
                SqlCommand command = new SqlCommand(saveQuery, connection);
                //istanzio e aggiungo il parametro @GUID
                SqlParameter guidParameter = new SqlParameter("@GUID", SqlDbType.UniqueIdentifier);
                guidParameter.Value = id == Guid.Empty ? SqlGuid.Null : id;
                guidParameter.Direction = ParameterDirection.InputOutput;
                command.Parameters.Add(guidParameter);
                //istanzio e aggiungo il parametro @ViewState
                SqlParameter viewStateParameter = new SqlParameter("@ViewState", SqlDbType.Text);
                viewStateParameter.Direction = ParameterDirection.Input;
                viewStateParameter.Value = stringToSave;
                command.Parameters.Add(viewStateParameter);
                //apro la connesione
                connection.Open();
                //eseguo l'inser o l'update
                command.ExecuteNonQuery();
                //chiudo la connessione
                connection.Close();
                //recupero il parametro di ritorno
                id = ((SqlGuid)guidParameter.Value).Value;
            }
            finally
            {
                if (connection.State != ConnectionState.Closed)
                {
                    connection.Close();
                }
            }
        }
    }

    [AspNetHostingPermission(SecurityAction.Demand, Level = AspNetHostingPermissionLevel.Minimal)]
    public class MyPageAdapter : System.Web.UI.Adapters.PageAdapter
    {

        public override PageStatePersister GetStatePersister()
        {
            return new SessionPageStatePersister(this.Page);
        }
    }
}