Professional ASP.NET 3.5 in C# and Visual Basic Part 110 docx

Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1048 Chapter 22: State Management Figure 22-4 Listing 22-5: A serializable object that can be used in the out-of-process Session VB < Serializable() > _ Public Class Person Public firstName As String Public lastName As String Public Overrides Function ToString() As String Return String.Format("Person Object: {0} {1}", firstName, lastName) End Function End Class 1048 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1049 Chapter 22: State Management C# [Serializable] public class Person { public string firstName; public string lastName; public override string ToString() { return String.Format("Person Object: {0} {1}", firstName, lastName); } } Because you put an instance of the Person class from Listing 22-5 into the Session object that is currently configured as StateServer , you should add a strongly typed property to the base Page class from Listing 22-3. In Listing 22-6 you see the strongly typed property added. Note the cast on the property Get ,and the strongly typed return value indicating that this property deals only with objects of type Person . Listing 22-6: Adding a strongly typed property to SmartSessionPage VB Public Class SmartSessionPage Inherits System.Web.UI.Page Private Const MYSESSIONPERSONKEY As String = "myperson" Public Property MyPerson() As Person Get Return CType(Session(MYSESSIONPERSONKEY), Person) End Get Set(ByVal value As Person) Session(MYSESSIONPERSONKEY) = value End Set End Property End Class C# public class SmartSessionPage : System.Web.UI.Page { private const string MYPERSON = "myperson"; public Person MyPerson { get { return (Person)Session[MYPERSON]; } set { Session[MYPERSON] = value; } } } 1049 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1050 Chapter 22: State Management Now, add code to create a new Person , populate its fields from the text box, and put the instance into the now-out-of-process Session State Service. Then, retrieve the Person and write its values out to the browser using the overloaded ToString() method from Listing 22-5. Certain classes in the Framework Class Library are not marked as serializable. If you use objects of this type within your own objects, these objects are not serializable at all. For example, if you include a DataRow field in a class and add your object to the State Service, you receive a message telling you it ‘‘ isnot marked as serializable’’ because the DataRow includes objects that are not serializable. In Listing 22-7, the value of the TextBox is split into a string array and the first two strings are put into a Person instance. For example, if you entered "Scott Hanselman" as a value, "Scott" is put into Per- son.firstName and "Hanselman" is put into Person.lastName . The values you enter should appear when they are retrieved later in Retrieve.aspx and written out to the browser with the overloaded ToString method. Listing 22-7: Setting and retrieving objects from the Session using State Service and a base page VB — Default.aspx.vb Partial Class _Default Inherits SmartSessionPage Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Dim names As String() names = TextBox1.Text.Split(" "c) ’ " "c creates a char Dim p As New Person() p.firstName = names(0) p.lastName = names(1) Session("myperson") = p End Sub End Class VB — Retrieve.aspx.vb Partial Class Retrieve Inherits SmartSessionPage Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) _ Handles Me.Load Dim p As Person = MyPerson Response.Write(p) ’ ToString will be called! End Sub End Class C# — Default.aspx.cs public partial class _Default : SmartSessionPage { protected void Button1_Click(object sender, EventArgs e) 1050 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1051 Chapter 22: State Management { string[] names = TextBox1.Text.Split(’ ’); Person p = new Person(); p.firstName = names[0]; p.lastName = names[1]; Session["myperson"] = p; } } C# — Retrieve.aspx.cs public partial class Retrieve : SmartSessionPage { protected void Page_Load(object sender, EventArgs e) { Person p = MyPerson; Response.Write(p); //ToString will be called! } } Now, launch the browser, enter your name (or "Scott Hanselman" if you like), click the button to store it in the Session ,andthenvisit Retrieve.aspx via the hyperlink. You see the result of the ToString() method via Response.Write , as shown in Figure 22-5. The completed code and techniques shown in Listing 22-7 illustrate a number of best practices for session management: ❑ Mark your objects as Serializable if you might ever use non-In-Proc session state. ❑ Even better, do all your development with a local session state server. This forces you to discover non-serializable objects early, gives you a sense of the performance and memory usages of asp- net_state.exe , and allows you to choose from any of the session options at deployment time. ❑ Use a base Page class or helper object with strongly typed properties to simplify your code. It enables you to hide the casts made to session keys otherwise referenced throughout your code. These best practices apply to all state storage methods, including SQL session state. SQL-Backed Session State ASP.NET sessions can also be stored in a SQL Server database. InProc offers speed, StateServer offers a resilience/speed balance, and storing sessions in SQL Server offers resilience that can serve sessions to a large Web farm that persists across IIS restarts, if necessary. SQL-backed session state is configured with aspnet_regsql.exe . This tool adds and removes sup- port for a number of ASP.NET features such as cache dependency (see Chapter 23) and personaliza- tion/membership (see Chapters 17 and 18) as well as session support. When you run aspnet_regsql.exe from the command line without any options, surprisingly, it pops up a GUI as shown in Figure 22-6. This utility is located in the .NET Framework’s installed directory, usually c: \ windows \ microsoft.net \ framework \ 2.0 . Note that the Framework 3.5 includes additional libraries, but this wizard is still in the 2.0 directory. 1051 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1052 Chapter 22: State Management Figure 22-5 The text of the dialog shown in Figure 22-6 contains instructions to run aspnet_regsql from the com- mand line with a "-?" switch. You have a huge number of options, so you’ll want to pipe it through in a form like aspnet_regsql -? | more . You see the session-state–specific options shown here: SESSION STATE OPTIONS -ssadd Add support for SQLServer mode session state. -ssremove Remove support for SQLServer mode session state. -sstype t|p|c Type of session state support: t: temporary. Session state data is stored in the "tempdb" database. Stored procedures for managing session are installed in the "ASPState" database. Data is not persisted if you restart SQL. (Default) 1052 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1053 Chapter 22: State Management p: persisted. Both session state data and the stored procedures are stored in the "ASPState" database. c: custom. Both session state data and the stored procedures are stored in a custom database. The database name must be specified. -d < database > The name of the custom database to use if -sstype is "c". Figure 22-6 Three options exist for session state support: t , p ,and c . The most significant difference is that the -sstype t option does not persist session state data across SQL Server restarts, whereas the -sstype p option does. Alternatively, you can specify a custom database with the -c option and give the database name with -d database . The following command-line example configures your system for SQL session support with the SQL Server on localhost with an sa password of wrox and a persistent store in the ASPState database. (Cer- tainly, you know not to deploy your system using sa and a weak password, but this simplifies the example. Ideally you’d use Windows Integration Authentication and give the Worker Process Identity access to the ASPState database.) If you’re using SQL Express, replace ‘‘localhost’’ with ‘‘.\SQLEXPRESS’’. If you aren’t using Windows Authentication, you may need to explicitly enable the sa account from the Management Studio, run this tool, and then disable the sa account for security reasons. 1053 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1054 Chapter 22: State Management C: \ > aspnet_regsql -S localhost -U sa -P wrox -ssadd -sstype p Start adding session state. Finished. Next, open up Enterprise Manager and look at the newly created database. Two tables are created — ASPStateTempApplications and ASPStateTempSessions — as well as a series of stored procedures to support moving the session back and forth from SQL to memory. If your SQL Server has its security locked down tight, you might get an Error 15501 after e xecuting asp- net_regsql.exe that says ‘‘An error occurred during the execution of the SQL file ’InstallSqlState.sql’.’’ The SQL error number is 15501 and the SqlException message is: This module has been marked OFF. Turn on ’Agent XPs’ in order to be able to access the module. If the job does not exist, an error from msdb.dbo.sp_delete_job is expected. This is a rather obscure message, but aspnet_regsql.exe is trying to tell you that the extended stored procedures it needs to enable session state are not enabled for security reasons. You’ll need to allow them explicitly. To do so, execute the following commands within the SQL Server 2005 Query Analyzer or the SQL Server 2005 Express Manager: USE master EXECUTE sp_configure ’show advanced options’, 1 RECONFIGURE WITH OVERRIDE GO EXECUTE sp_configure ’Agent XPs’, 1 RECONFIGURE WITH OVERRIDE GO EXECUTE sp_configure ’show advanced options’, 0 RECONFIGURE WITH OVERRIDE GO Now, change the web.config < sessionState > element to use SQL Server, as well as the new connection string: < sessionState mode="SQLServer" sqlConnectionString="data source=127.0.0.1;user id=sa;password=Wrox"/ > The session code shown in Listing 22-7 continues to work as before. However, if you open up the ASPStateTempSessions table, you see the serialized objects. Notice in Figure 22-7 that t he Session ID from the trace appears as a primary key in a row in the ASPStateTempSessions table. Figure 22-7 shows the SessionId as seen in the Request Details of ASP.NET t racing. That SessionId appears in the SessionId column of the ASPStateTempSessions table in the ASPState database just created. Notice also the ASPStateTempApplications table that keeps track of each IIS application that may be using the same database to manage sessions. 1054 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1055 Chapter 22: State Management If you want to use your own database to store session state, you specify the database name with the -d < database > switch of aspnet_regsql.exe and include the allowCustomSqlDatabase="true" attribute and the name of the database in the connection string: < sessionState allowCustomSqlDatabase="true" mode="SQLServer" sqlConnectionString="data source=127.0.0.1; database=MyCustomASPStateDatabase;"/ > Figure 22-7 1055 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1056 Chapter 22: State Management The user ID and password can be included in the connection string; or Windows Integrated Security can be used if the ASP.NET Worker Process’s identity is configured with access in SQL Server. Extending Session State with Other Providers ASP.NET Session State is built on a new, extensible, provider-based storage model. You can implement custom providers that store session data in other storage mechanisms simply by deriving from Session- StateStoreProviderBase . This extensibility feature also allows you to generate session IDs via your own algorithms by implementing ISessionIDManager . You start by creating a class that inherits from SessionStateStoreProviderBase . The session module will call methods on any session provider as long as it derives from SessionStateStoreProviderBase . Register your custom provider in your application’s web.config , as in the following example: < sessionState mode ="Custom" customProvider ="WroxProvider" > < providers > < add name ="WroxProvider" type ="Wrox.WroxStore, WroxSessionSupplier"/ > < /providers > < /sessionState > ASP.NET initializes the SessionStateModule , and these methods are called o n any custom implementation: ❑ Initialize : This method is inherited ultimately from System.Configuration.Provider .ProviderBase and is called immediately after the constructor. With this method, you set your provider name and call up to the base implementation of Initialize . ❑ SetItemExpireCallback : With this method, you can register any methods to be called when a session item expires. ❑ InitializeRequest : This method is called by the SessionStateModule for each request. This is an early opportunity to get ready for any requests for data that are coming. ❑ CreateNewStoreData : With this method, you create a new instance of SessionStateStoreData , the data structure that holds session items, the session timeout values, and any static items. When a session item is requested, ASP.NET calls your implementation to retrieve it. Implement the following methods to retrieve items: ❑ GetItemExclusive : This method enables you to get SessionStateStoreData from your chosen store. You may have created an Oracle provider, stored data in XML, or stored data elsewhere. ❑ GetItem : This is your opportunity to retrieve it as you did in GetItemExclusive except without exclusive locking. You may or may not care, depending on what backing store you’ve chosen. When it’s time to store an item, the following method is called: ❑ SetAndReleaseItemExculsive: Here you should save the SessionStateStoreData object to your custom store. A number of third-party session state providers are available — both open source and for sale. 1056 Evjen c22.tex V2 - 01/28/2008 3:19pm Page 1057 Chapter 22: State Management ScaleOut Software released the first third-party ASP.NET State Provider in the form of their StateServer product. It fills a niche between the ASP.NET included singleton StateServer and the SQL Server Database State Provider. ScaleOut Software’s StateServer is an out-of-process service that runs on each machine in the Web farm and ensures that session state is stored in a transparent and distributed manner among machines in the farm. You can learn more about StateServer and their ASP.NET 2.0 Session Provider at www.scaleoutsoftware.com/ . Another commercial product is StrangeLoop Network’s AppScaler. It includes an ASP.NET Session Provider that plugs into their network acceleration appliance. Their product also optimizes ViewState among other things and won a ’’Best of TechEd 2007’’ award. Details are a t www.strangeloopnetworks.com/ . The derivation-based provider module for things such as session state will no doubt continue to create a rich ecosystem of enthusiasts who will help push the functionality to new places Microsoft did not expect. Cookieless Session State In the previous example, the ASP.NET Session State ID was stored in a cookie. Some devices don’t sup- port cookies, or a user may have turned off cookie support in his browser. Cookies are convenient because the values are passed back and forth with every request and response. That means every HttpRequest contains cookie values, and every HttpResponse contains cookie values. What is the only other thing that is passed back and forth with every Request and Response ?TheURL. If you include the cookieless="UseUri" attribute in the web.config , ASP.NET does not send the ASP.NET Session ID back as a cookie. Instead, it modifies every URL to include the Session ID just before the requested page: < sessionState mode="SQLServer" cookieless="UseUri" sqlConnectionString="data source=127.0.0.1;user id=sa;password=Wrox" >< /sessionState > Notice that the Session ID appears in the URL as if it were a directory of its own situated between the actual Web site virtual directory and the page. With this change, server-side user controls such as the HyperLink control, used in Listing 22-1, have their properties automatically modified. The link in Listing 22-1 could have been hard-coded as HTML directly in the Designer, but then ASP.NET could not modify the target URL shown in Figure 22-8. The Session ID is a string that contains only the ASCII characters allowed in a URL. That makes sense when you realize that moving from a cookie-based Session-State system to a cookieless system requires putting that Session State value in the URL. Notice in Figure 22-8 that the request URL contains a Session ID within parentheses. One disadvantage to cookieless Sessions is how easily they can be tampered with. Certainly, cookies can be tampered with using HTTP sniffers, but URLS can be edited by anyone. The only way Session State is maintained is if every URL includes the Session ID in this way. 1057 . the overloaded ToString method. Listing 22-7: Setting and retrieving objects from the Session using State Service and a base page VB — Default.aspx.vb Partial Class _Default Inherits SmartSessionPage Protected. because the DataRow includes objects that are not serializable. In Listing 22-7, the value of the TextBox is split into a string array and the first two strings are put into a Person instance. For example,. When you run aspnet_regsql.exe from the command line without any options, surprisingly, it pops up a GUI as shown in Figure 22-6. This utility is located in the .NET Framework’s installed directory,