How to: Sample Session-State Store Provider
Demonstrates a session-state store provider implementation.
The following code example program shows how to implement a session-state store provider. For details about how to build this provider and use it in an ASP.NET application, see Sample Session-State Store Provider.
Example
Imports System
Imports System.Web
Imports System.Web.Configuration
Imports System.Configuration
Imports System.Collections.Specialized
Imports System.Web.SessionState
Imports System.Data
Imports System.Data.Odbc
Imports System.Diagnostics
Imports System.IO
' This session state store provider supports the following schema:
'
' CREATE TABLE Sessions
' (
' SessionId Text(80) NOT NULL,
' ApplicationName Text(255) NOT NULL,
' Created DateTime NOT NULL,
' Expires DateTime NOT NULL,
' LockDate DateTime NOT NULL,
' LockId Integer NOT NULL,
' Timeout Integer NOT NULL,
' Locked YesNo NOT NULL,
' SessionItems Memo,
' Flags Integer NOT NULL,
' CONSTRAINT PKSessions PRIMARY KEY (SessionId, ApplicationName)
' )
'
' This session state store provider does not automatically clean up
' expired session item data. It is recommended
' that you periodically delete expired session information from the
' data store with the following code (where 'conn' is the OdbcConnection
' for the session state store provider):
'
' Dim commandString As String = "DELETE FROM Sessions WHERE Expires < ?"
' Dim conn As OdbcConnection = New OdbcConnection(connectionString)
' Dim cmd As OdbcCommand = New OdbcCommand(commandString, conn)
' cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value = DateTime.Now
' conn.Open()
' cmd.ExecuteNonQuery()
' conn.Close()
Namespace Samples.AspNet.Session
Public NotInheritable Class OdbcSessionStateStore
Inherits SessionStateStoreProviderBase
Private pConfig As SessionStateSection = Nothing
Private connectionString As String
Private pConnectionStringSettings As ConnectionStringSettings
Private eventSource As String = "OdbcSessionStateStore"
Private eventLog As String = "Application"
Private exceptionMessage As String = _
"An exception occurred. Please contact your administrator."
Private pApplicationName As String
'
' If False, exceptions are thrown to the caller. If True,
' exceptions are written to the event log.
'
Private pWriteExceptionsToEventLog As Boolean = False
Public Property WriteExceptionsToEventLog As Boolean
Get
Return pWriteExceptionsToEventLog
End Get
Set
pWriteExceptionsToEventLog = value
End Set
End Property
'
' The ApplicationName property is used to differentiate sessions
' in the data source by application.
'
Public ReadOnly Property ApplicationName As String
Get
Return pApplicationName
End Get
End Property
'
' ProviderBase members
'
Public Overrides Sub Initialize(name As String, config As NameValueCollection)
'
' Initialize values from web.config.
'
If config Is Nothing Then _
Throw New ArgumentNullException("config")
If name Is Nothing OrElse name.Length = 0 Then _
name = "OdbcSessionStateStore"
If String.IsNullOrEmpty(config("description")) Then
config.Remove("description")
config.Add("description", "Sample ODBC Session State Store provider")
End If
' Initialize the abstract base class.
MyBase.Initialize(name, config)
'
' Initialize the ApplicationName property.
'
pApplicationName = _
System.Web.Hosting.HostingEnvironment.ApplicationVirtualPath
'
' Get <sessionState> configuration element.
'
Dim cfg As System.Configuration.Configuration = _
WebConfigurationManager.OpenWebConfiguration(ApplicationName)
pConfig = _
CType(cfg.GetSection("system.web/sessionState"), SessionStateSection)
'
' Initialize OdbcConnection.
'
pConnectionStringSettings = _
ConfigurationManager.ConnectionStrings(config("connectionStringName"))
If pConnectionStringSettings Is Nothing OrElse _
pConnectionStringSettings.ConnectionString.Trim() = "" Then
Throw New HttpException("Connection string cannot be blank.")
End If
connectionString = pConnectionStringSettings.ConnectionString
'
' Initialize WriteExceptionsToEventLog
'
pWriteExceptionsToEventLog = False
If Not config("writeExceptionsToEventLog") Is Nothing Then
If config("writeExceptionsToEventLog").ToUpper() = "TRUE" Then _
pWriteExceptionsToEventLog = True
End If
End Sub
'
' SessionStateStoreProviderBase members
'
Public Overrides Sub Dispose()
End Sub
'
' SessionStateProviderBase.SetItemExpireCallback
'
Public Overrides Function SetItemExpireCallback( _
expireCallback As SessionStateItemExpireCallback) As Boolean
Return False
End Function
'
' SessionStateProviderBase.SetAndReleaseItemExclusive
'
Public Overrides Sub SetAndReleaseItemExclusive(context As HttpContext, _
id As String, _
item As SessionStateStoreData, _
lockId As Object, _
newItem As Boolean)
' Serialize the SessionStateItemCollection as a string.
Dim sessItems As String = Serialize(CType(item.Items, SessionStateItemCollection))
Dim conn As OdbcConnection = New OdbcConnection(connectionString)
Dim cmd As OdbcCommand
Dim deleteCmd As OdbcCommand = Nothing
If newItem Then
' OdbcCommand to clear an existing expired session if it exists.
deleteCmd = New OdbcCommand("DELETE FROM Sessions " & _
"WHERE SessionId = ? AND ApplicationName = ? AND Expires < ?", conn)
deleteCmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
deleteCmd.Parameters.Add( _
"@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName
deleteCmd.Parameters.Add( _
"@Expires", OdbcType.DateTime).Value = DateTime.Now
' OdbcCommand to insert the New session item.
cmd = New OdbcCommand("INSERT INTO Sessions " & _
" (SessionId, ApplicationName, Created, Expires, " & _
" LockDate, LockId, Timeout, Locked, SessionItems, Flags) " & _
" Values(?, ?, ?, ?, ?, ? , ?, ?, ?, ?)", conn)
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add( _
"@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName
cmd.Parameters.Add( _
"@Created", OdbcType.DateTime).Value = DateTime.Now
cmd.Parameters.Add( _
"@Expires", OdbcType.DateTime).Value = DateTime.Now.AddMinutes(CDbl(item.Timeout))
cmd.Parameters.Add( _
"@LockDate", OdbcType.DateTime).Value = DateTime.Now
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = 0
cmd.Parameters.Add( _
"@Timeout", OdbcType.Int).Value = item.Timeout
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = False
cmd.Parameters.Add( _
"@SessionItems", OdbcType.VarChar, sessItems.Length).Value = sessItems
cmd.Parameters.Add("@Flags", OdbcType.Int).Value = 0
Else
' OdbcCommand to update the existing session item.
cmd = New OdbcCommand( _
"UPDATE Sessions SET Expires = ?, SessionItems = ?, Locked = ? " & _
" WHERE SessionId = ? AND ApplicationName = ? AND LockId = ?", conn)
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value = _
DateTime.Now.AddMinutes(CDbl(item.Timeout))
cmd.Parameters.Add("@SessionItems", _
OdbcType.VarChar, sessItems.Length).Value = sessItems
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = False
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add( _
"@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId
End If
Try
conn.Open()
If Not deleteCmd Is Nothing Then _
deleteCmd.ExecuteNonQuery()
cmd.ExecuteNonQuery()
Catch e As OdbcException
If WriteExceptionsToEventLog Then
WriteToEventLog(e, "SetAndReleaseItemExclusive")
Throw New Exception(exceptionMessage)
Else
Throw e
End If
Finally
conn.Close()
End Try
End Sub
'
' SessionStateProviderBase.GetItem
'
Public Overrides Function GetItem(context As HttpContext, _
id As String, _
ByRef locked As Boolean, _
ByRef lockAge As TimeSpan, _
ByRef lockId As Object, _
ByRef actionFlags As SessionStateActions) _
As SessionStateStoreData
Return GetSessionStoreItem(False, context, id, locked, lockAge, lockId, actionFlags)
End Function
'
' SessionStateProviderBase.GetItemExclusive
'
Public Overrides Function GetItemExclusive(context As HttpContext, _
id As String, _
ByRef locked As Boolean, _
ByRef lockAge As TimeSpan, _
ByRef lockId As Object, _
ByRef actionFlags As SessionStateActions) _
As SessionStateStoreData
Return GetSessionStoreItem(True, context, id, locked, lockAge, lockId, actionFlags)
End Function
'
' GetSessionStoreItem is called by both the GetItem and
' GetItemExclusive methods. GetSessionStoreItem retrieves the
' session data from the data source. If the lockRecord parameter
' is True (in the case of GetItemExclusive), then GetSessionStoreItem
' locks the record and sets a New LockId and LockDate.
'
Private Function GetSessionStoreItem(lockRecord As Boolean, _
context As HttpContext, _
id As String, _
ByRef locked As Boolean, _
ByRef lockAge As TimeSpan, _
ByRef lockId As Object, _
ByRef actionFlags As SessionStateActions) _
As SessionStateStoreData
' Initial values for Return value and out parameters.
Dim item As SessionStateStoreData = Nothing
lockAge = TimeSpan.Zero
lockId = Nothing
locked = False
actionFlags = 0
' Connection to ODBC database.
Dim conn As OdbcConnection = New OdbcConnection(connectionString)
' OdbcCommand for database commands.
Dim cmd As OdbcCommand = Nothing
' DataReader to read database record.
Dim reader As OdbcDataReader = Nothing
' DateTime to check if current session item is expired.
Dim expires As DateTime
' String to hold serialized SessionStateItemCollection.
Dim serializedItems As String = ""
' True if a record is found in the database.
Dim foundRecord As Boolean = False
' True if the returned session item is expired and needs to be deleted.
Dim deleteData As Boolean = False
' Timeout value from the data store.
Dim timeout As Integer = 0
Try
conn.Open()
' lockRecord is True when called from GetItemExclusive and
' False when called from GetItem.
' Obtain a lock if possible. Ignore the record if it is expired.
If lockRecord Then
cmd = New OdbcCommand( _
"UPDATE Sessions SET" & _
" Locked = ?, LockDate = ? " & _
" WHERE SessionId = ? AND ApplicationName = ? AND Locked = ? AND Expires > ?", conn)
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = True
cmd.Parameters.Add("@LockDate", OdbcType.DateTime).Value = _
DateTime.Now
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, _
255).Value = ApplicationName
cmd.Parameters.Add("@Locked", OdbcType.Int).Value = False
cmd.Parameters.Add( _
"@Expires", OdbcType.DateTime).Value = DateTime.Now
If cmd.ExecuteNonQuery() = 0 Then
' No record was updated because the record was locked or not found.
locked = True
Else
' The record was updated.
locked = False
End If
End If
' Retrieve the current session item information.
cmd = New OdbcCommand( _
"SELECT Expires, SessionItems, LockId, LockDate, Flags, Timeout " & _
" FROM Sessions " & _
" WHERE SessionId = ? AND ApplicationName = ?", conn)
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, _
255).Value = ApplicationName
' Retrieve session item data from the data source.
reader = cmd.ExecuteReader(CommandBehavior.SingleRow)
Do While reader.Read()
expires = reader.GetDateTime(0)
If expires < DateTime.Now Then
' The record was expired. Mark it as not locked.
locked = False
' The session was expired. Mark the data for deletion.
deleteData = True
Else
foundRecord = True
End If
serializedItems = reader.GetString(1)
lockId = reader.GetInt32(2)
lockAge = DateTime.Now.Subtract(reader.GetDateTime(3))
actionFlags = CType(reader.GetInt32(4), SessionStateActions)
timeout = reader.GetInt32(5)
Loop
reader.Close()
' If the returned session item is expired,
' delete the record from the data source.
If deleteData Then
cmd = New OdbcCommand("DELETE FROM Sessions " & _
"WHERE SessionId = ? AND ApplicationName = ?", conn)
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, _
255).Value = ApplicationName
cmd.ExecuteNonQuery()
End If
' The record was not found. Ensure that locked is False.
If Not foundRecord Then _
locked = False
' If the record was found and you obtained a lock, then set
' the lockId, clear the actionFlags,
' and create the SessionStateStoreItem to return.
If foundRecord AndAlso Not locked Then
lockId = CInt(lockId) + 1
cmd = New OdbcCommand("UPDATE Sessions SET" & _
" LockId = ?, Flags = 0 " & _
" WHERE SessionId = ? AND ApplicationName = ?", conn)
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName
cmd.ExecuteNonQuery()
' If the actionFlags parameter is not InitializeItem,
' deserialize the stored SessionStateItemCollection.
If actionFlags = SessionStateActions.InitializeItem Then
item = CreateNewStoreData(context, pConfig.Timeout.Minutes)
Else
item = Deserialize(context, serializedItems, timeout)
End If
End If
Catch e As OdbcException
If WriteExceptionsToEventLog Then
WriteToEventLog(e, "GetSessionStoreItem")
Throw New Exception(exceptionMessage)
Else
Throw e
End If
Finally
If Not reader Is Nothing Then reader.Close()
conn.Close()
End Try
Return item
End Function
'
' Serialize is called by the SetAndReleaseItemExclusive method to
' convert the SessionStateItemCollection into a Base64 string to
' be stored in an Access Memo field.
'
Private Function Serialize(items As SessionStateItemCollection) As String
Dim ms As MemoryStream = New MemoryStream()
Dim writer As BinaryWriter = New BinaryWriter(ms)
If Not items Is Nothing Then _
items.Serialize(writer)
writer.Close()
Return Convert.ToBase64String(ms.ToArray())
End Function
'
' Deserialize is called by the GetSessionStoreItem method to
' convert the Base64 string stored in the Access Memo field to a
' SessionStateItemCollection.
'
Private Function Deserialize(context As HttpContext, _
serializedItems As String, timeout As Integer) As SessionStateStoreData
Dim ms As MemoryStream = _
New MemoryStream(Convert.FromBase64String(serializedItems))
Dim sessionItems As SessionStateItemCollection = _
New SessionStateItemCollection()
If ms.Length > 0 Then
Dim reader As BinaryReader = New BinaryReader(ms)
sessionItems = SessionStateItemCollection.Deserialize(reader)
End If
Return New SessionStateStoreData(sessionItems, _
SessionStateUtility.GetSessionStaticObjects(context), _
timeout)
End Function
'
' SessionStateProviderBase.ReleaseItemExclusive
'
Public Overrides Sub ReleaseItemExclusive(context As HttpContext, _
id As String, _
lockId As Object)
Dim conn As OdbcConnection = New OdbcConnection(connectionString)
Dim cmd As OdbcCommand = _
New OdbcCommand("UPDATE Sessions SET Locked = 0, Expires = ? " & _
"WHERE SessionId = ? AND ApplicationName = ? AND LockId = ?", conn)
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value = _
DateTime.Now.AddMinutes(pConfig.Timeout.Minutes)
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, _
255).Value = ApplicationName
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId
Try
conn.Open()
cmd.ExecuteNonQuery()
Catch e As OdbcException
If WriteExceptionsToEventLog Then
WriteToEventLog(e, "ReleaseItemExclusive")
Throw New Exception(exceptionMessage)
Else
Throw e
End If
Finally
conn.Close()
End Try
End Sub
'
' SessionStateProviderBase.RemoveItem
'
Public Overrides Sub RemoveItem(context As HttpContext, _
id As String, _
lockId As Object, _
item As SessionStateStoreData)
Dim conn As OdbcConnection = New OdbcConnection(connectionString)
Dim cmd As OdbcCommand = New OdbcCommand("DELETE * FROM Sessions " & _
"WHERE SessionId = ? AND ApplicationName = ? AND LockId = ?", conn)
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, _
255).Value = ApplicationName
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId
Try
conn.Open()
cmd.ExecuteNonQuery()
Catch e As OdbcException
If WriteExceptionsToEventLog Then
WriteToEventLog(e, "RemoveItem")
Throw New Exception(exceptionMessage)
Else
Throw e
End If
Finally
conn.Close()
End Try
End Sub
'
' SessionStateProviderBase.CreateUninitializedItem
'
Public Overrides Sub CreateUninitializedItem(context As HttpContext, _
id As String, _
timeout As Integer)
Dim conn As OdbcConnection = New OdbcConnection(connectionString)
Dim cmd As OdbcCommand = New OdbcCommand("INSERT INTO Sessions " & _
" (SessionId, ApplicationName, Created, Expires, " & _
" LockDate, LockId, Timeout, Locked, SessionItems, Flags) " & _
" Values(?, ?, ?, ?, ?, ? , ?, ?, ?, ?)", conn)
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, _
255).Value = ApplicationName
cmd.Parameters.Add("@Created", OdbcType.DateTime).Value = _
DateTime.Now
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value = _
DateTime.Now.AddMinutes(CDbl(timeout))
cmd.Parameters.Add("@LockDate", OdbcType.DateTime).Value = _
DateTime.Now
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = 0
cmd.Parameters.Add("@Timeout", OdbcType.Int).Value = timeout
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = False
cmd.Parameters.Add("@SessionItems", OdbcType.VarChar, 0).Value = ""
cmd.Parameters.Add("@Flags", OdbcType.Int).Value = 1
Try
conn.Open()
cmd.ExecuteNonQuery()
Catch e As OdbcException
If WriteExceptionsToEventLog Then
WriteToEventLog(e, "CreateUninitializedItem")
Throw New Exception(exceptionMessage)
Else
Throw e
End If
Finally
conn.Close()
End Try
End Sub
'
' SessionStateProviderBase.CreateNewStoreData
'
Public Overrides Function CreateNewStoreData( _
context As HttpContext, _
timeout As Integer) As SessionStateStoreData
Return New SessionStateStoreData(New SessionStateItemCollection(), _
SessionStateUtility.GetSessionStaticObjects(context), _
timeout)
End Function
'
' SessionStateProviderBase.ResetItemTimeout
'
Public Overrides Sub ResetItemTimeout(context As HttpContext, _
id As String)
Dim conn As OdbcConnection = New OdbcConnection(connectionString)
Dim cmd As OdbcCommand = _
New OdbcCommand("UPDATE Sessions SET Expires = ? " & _
"WHERE SessionId = ? AND ApplicationName = ?", conn)
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value = _
DateTime.Now.AddMinutes(pConfig.Timeout.Minutes)
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, _
255).Value = ApplicationName
Try
conn.Open()
cmd.ExecuteNonQuery()
Catch e As OdbcException
If WriteExceptionsToEventLog Then
WriteToEventLog(e, "ResetItemTimeout")
Throw New Exception(exceptionMessage)
Else
Throw e
End If
Finally
conn.Close()
End Try
End Sub
'
' SessionStateProviderBase.InitializeRequest
'
Public Overrides Sub InitializeRequest(context As HttpContext)
End Sub
'
' SessionStateProviderBase.EndRequest
'
Public Overrides Sub EndRequest(context As HttpContext)
End Sub
'
' WriteToEventLog
' This is a helper function that writes exception detail to the
' event log. Exceptions are written to the event log as a security
' measure to ensure Private database details are not returned to
' browser. If a method does not Return a status or Boolean
' indicating the action succeeded or failed, the caller also
' throws a generic exception.
'
Private Sub WriteToEventLog(e As Exception, action As String)
Dim log As EventLog = New EventLog()
log.Source = eventSource
log.Log = eventLog
Dim message As String = _
"An exception occurred communicating with the data source." & vbCrLf & vbCrLf
message &= "Action: " & action & vbCrLf & vbCrLf
message &= "Exception: " & e.ToString()
log.WriteEntry(message)
End Sub
End Class
End Namespace
using System;
using System.Web;
using System.Web.Configuration;
using System.Configuration;
using System.Configuration.Provider;
using System.Collections.Specialized;
using System.Web.SessionState;
using System.Data;
using System.Data.Odbc;
using System.Diagnostics;
using System.IO;
/*
This session state store provider supports the following schema:
CREATE TABLE Sessions
(
SessionId Text(80) NOT NULL,
ApplicationName Text(255) NOT NULL,
Created DateTime NOT NULL,
Expires DateTime NOT NULL,
LockDate DateTime NOT NULL,
LockId Integer NOT NULL,
Timeout Integer NOT NULL,
Locked YesNo NOT NULL,
SessionItems Memo,
Flags Integer NOT NULL,
CONSTRAINT PKSessions PRIMARY KEY (SessionId, ApplicationName)
)
This session state store provider does not automatically clean up
expired session item data. It is recommended
that you periodically delete expired session information from the
data store with the following code (where 'conn' is the OdbcConnection
for the session state store provider):
string commandString = "DELETE FROM Sessions WHERE Expires < ?";
OdbcConnection conn = new OdbcConnection(connectionString);
OdbcCommand cmd = new OdbcCommand(commandString, conn);
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value = DateTime.Now;
conn.Open();
cmd.ExecuteNonQuery();
conn.Close();
*/
namespace Samples.AspNet.Session
{
public sealed class OdbcSessionStateStore : SessionStateStoreProviderBase
{
private SessionStateSection pConfig = null;
private string connectionString;
private ConnectionStringSettings pConnectionStringSettings;
private string eventSource = "OdbcSessionStateStore";
private string eventLog = "Application";
private string exceptionMessage =
"An exception occurred. Please contact your administrator.";
private string pApplicationName;
//
// If false, exceptions are thrown to the caller. If true,
// exceptions are written to the event log.
//
private bool pWriteExceptionsToEventLog = false;
public bool WriteExceptionsToEventLog
{
get { return pWriteExceptionsToEventLog; }
set { pWriteExceptionsToEventLog = value; }
}
//
// The ApplicationName property is used to differentiate sessions
// in the data source by application.
//
public string ApplicationName
{
get { return pApplicationName; }
}
public override void Initialize(string name, NameValueCollection config)
{
//
// Initialize values from web.config.
//
if (config == null)
throw new ArgumentNullException("config");
if (name == null || name.Length == 0)
name = "OdbcSessionStateStore";
if (String.IsNullOrEmpty(config["description"]))
{
config.Remove("description");
config.Add("description", "Sample ODBC Session State Store provider");
}
// Initialize the abstract base class.
base.Initialize(name, config);
//
// Initialize the ApplicationName property.
//
pApplicationName =
System.Web.Hosting.HostingEnvironment.ApplicationVirtualPath;
//
// Get <sessionState> configuration element.
//
Configuration cfg =
WebConfigurationManager.OpenWebConfiguration(ApplicationName);
pConfig =
(SessionStateSection)cfg.GetSection("system.web/sessionState");
//
// Initialize connection string.
//
pConnectionStringSettings =
ConfigurationManager.ConnectionStrings[config["connectionStringName"]];
if (pConnectionStringSettings == null ||
pConnectionStringSettings.ConnectionString.Trim() == "")
{
throw new ProviderException("Connection string cannot be blank.");
}
connectionString = pConnectionStringSettings.ConnectionString;
//
// Initialize WriteExceptionsToEventLog
//
pWriteExceptionsToEventLog = false;
if (config["writeExceptionsToEventLog"] != null)
{
if (config["writeExceptionsToEventLog"].ToUpper() == "TRUE")
pWriteExceptionsToEventLog = true;
}
}
//
// SessionStateStoreProviderBase members
//
public override void Dispose()
{
}
//
// SessionStateProviderBase.SetItemExpireCallback
//
public override bool SetItemExpireCallback(SessionStateItemExpireCallback expireCallback)
{
return false;
}
//
// SessionStateProviderBase.SetAndReleaseItemExclusive
//
public override void SetAndReleaseItemExclusive(HttpContext context,
string id,
SessionStateStoreData item,
object lockId,
bool newItem)
{
// Serialize the SessionStateItemCollection as a string.
string sessItems = Serialize((SessionStateItemCollection)item.Items);
OdbcConnection conn = new OdbcConnection(connectionString);
OdbcCommand cmd;
OdbcCommand deleteCmd = null;
if (newItem)
{
// OdbcCommand to clear an existing expired session if it exists.
deleteCmd = new OdbcCommand("DELETE FROM Sessions " +
"WHERE SessionId = ? AND ApplicationName = ? AND Expires < ?", conn);
deleteCmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
deleteCmd.Parameters.Add
("@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName;
deleteCmd.Parameters.Add
("@Expires", OdbcType.DateTime).Value = DateTime.Now;
// OdbcCommand to insert the new session item.
cmd = new OdbcCommand("INSERT INTO Sessions " +
" (SessionId, ApplicationName, Created, Expires, " +
" LockDate, LockId, Timeout, Locked, SessionItems, Flags) " +
" Values(?, ?, ?, ?, ?, ? , ?, ?, ?, ?)", conn);
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add
("@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName;
cmd.Parameters.Add
("@Created", OdbcType.DateTime).Value = DateTime.Now;
cmd.Parameters.Add
("@Expires", OdbcType.DateTime).Value = DateTime.Now.AddMinutes((Double)item.Timeout);
cmd.Parameters.Add
("@LockDate", OdbcType.DateTime).Value = DateTime.Now;
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = 0;
cmd.Parameters.Add
("@Timeout", OdbcType.Int).Value = item.Timeout;
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = false;
cmd.Parameters.Add
("@SessionItems", OdbcType.VarChar, sessItems.Length).Value = sessItems;
cmd.Parameters.Add("@Flags", OdbcType.Int).Value = 0;
}
else
{
// OdbcCommand to update the existing session item.
cmd = new OdbcCommand(
"UPDATE Sessions SET Expires = ?, SessionItems = ?, Locked = ? " +
" WHERE SessionId = ? AND ApplicationName = ? AND LockId = ?", conn);
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value =
DateTime.Now.AddMinutes((Double)item.Timeout);
cmd.Parameters.Add("@SessionItems",
OdbcType.VarChar, sessItems.Length).Value = sessItems;
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = false;
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId;
}
try
{
conn.Open();
if (deleteCmd != null)
deleteCmd.ExecuteNonQuery();
cmd.ExecuteNonQuery();
}
catch (OdbcException e)
{
if (WriteExceptionsToEventLog)
{
WriteToEventLog(e, "SetAndReleaseItemExclusive");
throw new ProviderException(exceptionMessage);
}
else
throw e;
}
finally
{
conn.Close();
}
}
//
// SessionStateProviderBase.GetItem
//
public override SessionStateStoreData GetItem(HttpContext context,
string id,
out bool locked,
out TimeSpan lockAge,
out object lockId,
out SessionStateActions actionFlags)
{
return GetSessionStoreItem(false, context, id, out locked,
out lockAge, out lockId, out actionFlags);
}
//
// SessionStateProviderBase.GetItemExclusive
//
public override SessionStateStoreData GetItemExclusive(HttpContext context,
string id,
out bool locked,
out TimeSpan lockAge,
out object lockId,
out SessionStateActions actionFlags)
{
return GetSessionStoreItem(true, context, id, out locked,
out lockAge, out lockId, out actionFlags);
}
//
// GetSessionStoreItem is called by both the GetItem and
// GetItemExclusive methods. GetSessionStoreItem retrieves the
// session data from the data source. If the lockRecord parameter
// is true (in the case of GetItemExclusive), then GetSessionStoreItem
// locks the record and sets a new LockId and LockDate.
//
private SessionStateStoreData GetSessionStoreItem(bool lockRecord,
HttpContext context,
string id,
out bool locked,
out TimeSpan lockAge,
out object lockId,
out SessionStateActions actionFlags)
{
// Initial values for return value and out parameters.
SessionStateStoreData item = null;
lockAge = TimeSpan.Zero;
lockId = null;
locked = false;
actionFlags = 0;
// ODBC database connection.
OdbcConnection conn = new OdbcConnection(connectionString);
// OdbcCommand for database commands.
OdbcCommand cmd = null;
// DataReader to read database record.
OdbcDataReader reader = null;
// DateTime to check if current session item is expired.
DateTime expires;
// String to hold serialized SessionStateItemCollection.
string serializedItems = "";
// True if a record is found in the database.
bool foundRecord = false;
// True if the returned session item is expired and needs to be deleted.
bool deleteData = false;
// Timeout value from the data store.
int timeout = 0;
try
{
conn.Open();
// lockRecord is true when called from GetItemExclusive and
// false when called from GetItem.
// Obtain a lock if possible. Ignore the record if it is expired.
if (lockRecord)
{
cmd = new OdbcCommand(
"UPDATE Sessions SET" +
" Locked = ?, LockDate = ? " +
" WHERE SessionId = ? AND ApplicationName = ? AND Locked = ? AND Expires > ?", conn);
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = true;
cmd.Parameters.Add("@LockDate", OdbcType.DateTime).Value
= DateTime.Now;
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
cmd.Parameters.Add("@Locked", OdbcType.Int).Value = false;
cmd.Parameters.Add
("@Expires", OdbcType.DateTime).Value = DateTime.Now;
if (cmd.ExecuteNonQuery() == 0)
// No record was updated because the record was locked or not found.
locked = true;
else
// The record was updated.
locked = false;
}
// Retrieve the current session item information.
cmd = new OdbcCommand(
"SELECT Expires, SessionItems, LockId, LockDate, Flags, Timeout " +
" FROM Sessions " +
" WHERE SessionId = ? AND ApplicationName = ?", conn);
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
// Retrieve session item data from the data source.
reader = cmd.ExecuteReader(CommandBehavior.SingleRow);
while (reader.Read())
{
expires = reader.GetDateTime(0);
if (expires < DateTime.Now)
{
// The record was expired. Mark it as not locked.
locked = false;
// The session was expired. Mark the data for deletion.
deleteData = true;
}
else
foundRecord = true;
serializedItems = reader.GetString(1);
lockId = reader.GetInt32(2);
lockAge = DateTime.Now.Subtract(reader.GetDateTime(3));
actionFlags = (SessionStateActions)reader.GetInt32(4);
timeout = reader.GetInt32(5);
}
reader.Close();
// If the returned session item is expired,
// delete the record from the data source.
if (deleteData)
{
cmd = new OdbcCommand("DELETE FROM Sessions " +
"WHERE SessionId = ? AND ApplicationName = ?", conn);
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
cmd.ExecuteNonQuery();
}
// The record was not found. Ensure that locked is false.
if (!foundRecord)
locked = false;
// If the record was found and you obtained a lock, then set
// the lockId, clear the actionFlags,
// and create the SessionStateStoreItem to return.
if (foundRecord && !locked)
{
lockId = (int)lockId + 1;
cmd = new OdbcCommand("UPDATE Sessions SET" +
" LockId = ?, Flags = 0 " +
" WHERE SessionId = ? AND ApplicationName = ?", conn);
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId;
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName;
cmd.ExecuteNonQuery();
// If the actionFlags parameter is not InitializeItem,
// deserialize the stored SessionStateItemCollection.
if (actionFlags == SessionStateActions.InitializeItem)
item = CreateNewStoreData(context, pConfig.Timeout.Minutes);
else
item = Deserialize(context, serializedItems, timeout);
}
}
catch (OdbcException e)
{
if (WriteExceptionsToEventLog)
{
WriteToEventLog(e, "GetSessionStoreItem");
throw new ProviderException(exceptionMessage);
}
else
throw e;
}
finally
{
if (reader != null) { reader.Close(); }
conn.Close();
}
return item;
}
//
// Serialize is called by the SetAndReleaseItemExclusive method to
// convert the SessionStateItemCollection into a Base64 string to
// be stored in an Access Memo field.
//
private string Serialize(SessionStateItemCollection items)
{
MemoryStream ms = new MemoryStream();
BinaryWriter writer = new BinaryWriter(ms);
if (items != null)
items.Serialize(writer);
writer.Close();
return Convert.ToBase64String(ms.ToArray());
}
//
// DeSerialize is called by the GetSessionStoreItem method to
// convert the Base64 string stored in the Access Memo field to a
// SessionStateItemCollection.
//
private SessionStateStoreData Deserialize(HttpContext context,
string serializedItems, int timeout)
{
MemoryStream ms =
new MemoryStream(Convert.FromBase64String(serializedItems));
SessionStateItemCollection sessionItems =
new SessionStateItemCollection();
if (ms.Length > 0)
{
BinaryReader reader = new BinaryReader(ms);
sessionItems = SessionStateItemCollection.Deserialize(reader);
}
return new SessionStateStoreData(sessionItems,
SessionStateUtility.GetSessionStaticObjects(context),
timeout);
}
//
// SessionStateProviderBase.ReleaseItemExclusive
//
public override void ReleaseItemExclusive(HttpContext context,
string id,
object lockId)
{
OdbcConnection conn = new OdbcConnection(connectionString);
OdbcCommand cmd =
new OdbcCommand("UPDATE Sessions SET Locked = 0, Expires = ? " +
"WHERE SessionId = ? AND ApplicationName = ? AND LockId = ?", conn);
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value =
DateTime.Now.AddMinutes(pConfig.Timeout.Minutes);
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId;
try
{
conn.Open();
cmd.ExecuteNonQuery();
}
catch (OdbcException e)
{
if (WriteExceptionsToEventLog)
{
WriteToEventLog(e, "ReleaseItemExclusive");
throw new ProviderException(exceptionMessage);
}
else
throw e;
}
finally
{
conn.Close();
}
}
//
// SessionStateProviderBase.RemoveItem
//
public override void RemoveItem(HttpContext context,
string id,
object lockId,
SessionStateStoreData item)
{
OdbcConnection conn = new OdbcConnection(connectionString);
OdbcCommand cmd = new OdbcCommand("DELETE * FROM Sessions " +
"WHERE SessionId = ? AND ApplicationName = ? AND LockId = ?", conn);
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = lockId;
try
{
conn.Open();
cmd.ExecuteNonQuery();
}
catch (OdbcException e)
{
if (WriteExceptionsToEventLog)
{
WriteToEventLog(e, "RemoveItem");
throw new ProviderException(exceptionMessage);
}
else
throw e;
}
finally
{
conn.Close();
}
}
//
// SessionStateProviderBase.CreateUninitializedItem
//
public override void CreateUninitializedItem(HttpContext context,
string id,
int timeout)
{
OdbcConnection conn = new OdbcConnection(connectionString);
OdbcCommand cmd = new OdbcCommand("INSERT INTO Sessions " +
" (SessionId, ApplicationName, Created, Expires, " +
" LockDate, LockId, Timeout, Locked, SessionItems, Flags) " +
" Values(?, ?, ?, ?, ?, ? , ?, ?, ?, ?)", conn);
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
cmd.Parameters.Add("@Created", OdbcType.DateTime).Value
= DateTime.Now;
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value
= DateTime.Now.AddMinutes((Double)timeout);
cmd.Parameters.Add("@LockDate", OdbcType.DateTime).Value
= DateTime.Now;
cmd.Parameters.Add("@LockId", OdbcType.Int).Value = 0;
cmd.Parameters.Add("@Timeout", OdbcType.Int).Value = timeout;
cmd.Parameters.Add("@Locked", OdbcType.Bit).Value = false;
cmd.Parameters.Add("@SessionItems", OdbcType.VarChar, 0).Value = "";
cmd.Parameters.Add("@Flags", OdbcType.Int).Value = 1;
try
{
conn.Open();
cmd.ExecuteNonQuery();
}
catch (OdbcException e)
{
if (WriteExceptionsToEventLog)
{
WriteToEventLog(e, "CreateUninitializedItem");
throw new ProviderException(exceptionMessage);
}
else
throw e;
}
finally
{
conn.Close();
}
}
//
// SessionStateProviderBase.CreateNewStoreData
//
public override SessionStateStoreData CreateNewStoreData(
HttpContext context,
int timeout)
{
return new SessionStateStoreData(new SessionStateItemCollection(),
SessionStateUtility.GetSessionStaticObjects(context),
timeout);
}
//
// SessionStateProviderBase.ResetItemTimeout
//
public override void ResetItemTimeout(HttpContext context,
string id)
{
OdbcConnection conn = new OdbcConnection(connectionString);
OdbcCommand cmd =
new OdbcCommand("UPDATE Sessions SET Expires = ? " +
"WHERE SessionId = ? AND ApplicationName = ?", conn);
cmd.Parameters.Add("@Expires", OdbcType.DateTime).Value
= DateTime.Now.AddMinutes(pConfig.Timeout.Minutes);
cmd.Parameters.Add("@SessionId", OdbcType.VarChar, 80).Value = id;
cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar,
255).Value = ApplicationName;
try
{
conn.Open();
cmd.ExecuteNonQuery();
}
catch (OdbcException e)
{
if (WriteExceptionsToEventLog)
{
WriteToEventLog(e, "ResetItemTimeout");
throw new ProviderException(exceptionMessage);
}
else
throw e;
}
finally
{
conn.Close();
}
}
//
// SessionStateProviderBase.InitializeRequest
//
public override void InitializeRequest(HttpContext context)
{
}
//
// SessionStateProviderBase.EndRequest
//
public override void EndRequest(HttpContext context)
{
}
//
// WriteToEventLog
// This is a helper function that writes exception detail to the
// event log. Exceptions are written to the event log as a security
// measure to ensure private database details are not returned to
// browser. If a method does not return a status or Boolean
// indicating the action succeeded or failed, the caller also
// throws a generic exception.
//
private void WriteToEventLog(Exception e, string action)
{
EventLog log = new EventLog();
log.Source = eventSource;
log.Log = eventLog;
string message =
"An exception occurred communicating with the data source.\n\n";
message += "Action: " + action + "\n\n";
message += "Exception: " + e.ToString();
log.WriteEntry(message);
}
}
}
See Also
Concepts
Sample Session-State Store Provider
Implementing a Session-State Store Provider