asp.net the compiler failed with error code 128

asp.net the compiler failed with error code 128

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In some controls, disabling view state may break a feature you rely on Although the situation has improved with the creation of control state (a privileged section of view state used by the control, which you ll learn about in 27), some problems still remain This is particularly the case with existing controls, which sometimes can t be updated to use control state without introducing behavior changes that could break existing ASPNET 1x pages One example is how list controls such as ListBox and DropDownList track selection Imagine you create a page where you need to fill a drop-down list with hundreds of entries If the list isn t expensive to create (for example, if you re retrieving it directly from memory or the cache), you might choose to disable view state for the list control and rebuild the list at the beginning of each postback.

ASP .NET 2.0 introduces a new model for reading configuration files. It revolves around the new WebConfigurationManager and Configuration classes in the System.Web.Configuration namespace, which allow you to extract information from a configuration file at runtime. The WebConfigurationManager is the starting point. It provides the members shown in Table 5-3. Table 5-3. ConfigurationManager Members

o web application framework, no matter how advanced, can change that HTTP is a stateless protocol. After every web request, the client disconnects from the server, and the ASP .NET engine discards the page objects. This architecture ensures that web applications can scale up to serve thousands of simultaneous requests without running out of server memory. The drawback is that your code needs to use other techniques to store information between web requests and retrieve it when needed. In this chapter, you ll see how to tackle this challenge by maintaining information on the server and on the client using a variety of techniques. You ll also learn how to transfer information from one web page to another.

Here s an example that simply fills a list with numbers: protected void Page_Load(object sender, EventArgs e) { for (int i = 0; i < 1000; i++) { lstBigItemsAdd(iToString()); } } The problem this causes is that once you disable view state, you ensure that the user s list selection is lost every time the page is posted back That means you won t be able to retrieve any information from the SelectedIndex or SelectedItem properties Similarly, the SelectedIndexChanged event won't fire You have one way to remedy this problem Although the selection information is lost, the user s choice is actually still maintained in the RequestForms collection (a collection of posted values that s present for backward compatibility with ASP pages).

Provides access to any custom information you ve added to the <appSettings> section of the application configuration file. Individual settings are provided through a collection that s indexed by name. Provides access to data in the <connectionStrings> section of the configuration file. Individual settings are provided through a collection that s indexed by name. Returns a Configuration object that provides access to the configuration information for the specified web application. Returns a Configuration object that provides access to the configuration information that s defined for the web server (in the machine.config file). Discards any information that has been retrieved for the indicated section. Next time you read any of the section s information, the WebConfigurationManager will reread it from disk.

The standbys of state management remain the same in ASP.NET 2.0. That means the programming interface for session state, application state, view state, and the query string hasn t changed at all. However, session state now offers more configuration options, and you have a new way to transfer information between pages. Here s a preview of the changes: Cross-page postbacks: In ASP.NET 1.x, a page could post only to itself. In ASP.NET 2.0, you can post from one page to another, transferring the page s state at the same time. New session state settings: Session state is now more configurable. You have options that allow you to use a custom SQL Server database (instead of one named ASPState), set timeouts, and configure how cookies are used and named. Custom session state providers: Microsoft has opened the session state model so that you can develop custom session state providers (and session ID providers) that store state in other data sources or generate session IDs using different algorithms. Profiles: Rather than coding your own database retrieval logic, you can use the new profile API to store userspecific information in a database. Best of all, this information is strongly typed, unlike session state. Profiles build on the ASP.NET authentication model. Out of these four topics, you ll see only the first two in this chapter. 24 discusses profiles, because you need to use them in conjunction with Windows authentication or forms authentication. Custom session state providers are beyond the scope of this book. However, expect to see third-party session providers that allow you to use sessions with other relational databases.