ASP.NET Web PDF Document Viewer/Editor Control Library

<form id="Form1" runat="server" onload="Form1_Load"> The implementation of Form1_Load uses the IsPostBack property of the page object to detect whether the page is loaded for the first time or whether it is loaded in reaction to some event invoked by a control. The reaction to an event that involves executing server-side code is called a postback, and it is triggered by sending data from the client back to the current page. When the page is loaded for the first time, this event handler sets the content of this.Time. This is the label element of the page being presented to the user (note the close correspondence between ASP.NET elements and HTML elements). The second part of the script is the following member: member this.Reload_Click(sender: obj, e: EventArgs) = this.Time.Text <- "(R) " + DateTime.Now.ToString() This member is associated with the Reload button control and is invoked when the button is clicked. Because the event handler associated with the button has to be executed on the server, the page will be reloaded, and the event will be triggered. Note that the entire page is reloaded, so the Form1_Load handler will be called as well, but for this and subsequent reloads, the IsPostBack property is set to true and the label will not be updated by that event handler.

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IDbTransaction xaction = null; try { cn.Open(); xaction = cn.BeginTransaction(); db.ExecuteNonQuery(cwRoyal, xaction); db.ExecuteNonQuery(cwTitle, xaction); xaction.Commit(); } catch { if (xaction != null) xaction.Rollback(); } finally { cn.Close(); } } As you can see from the code, the Managed Provider transaction model has an extremely thin wrapper provided by the block. The preceding example takes control of the connection lifetime from the Database object. This works much the same way the DataAdapter.Fill method does. If the transaction is open when the Execute method is called, the Database object will use it and leave it open; otherwise, it opens, executes, and closes the connection. This method of transaction management will work only when all work is being done on a single connection. For transactions that span databases or data providers, Microsoft Distributed Transaction Coordinator (MSDTC) must be enrolled via COM+. For more information on transactions, see 7 for a discussion of distributed transactions, and 12 for an examination of the in-memory transaction model available in the .NET Framework 2.0 that automatically enrolls the resource managers needed as the scope of a transaction increases.

The following statement sets up the SQLJ runtime context. As of 10g Release 1, if you try to invoke the wrapper method without executing this statement, you will get the following exception: found null connection context. Note that this problem does not exist if you use JPublisher to generate wrapper methods that implement the ORAData and ORADataFactory interfaces (as you will see shortly). address.setConnectionContext( new sqlj.runtime.ref.DefaultContext(connection)); Note how we can use getAddress() without passing the Connection object. As shown earlier, JPublisher takes care of passing the connection object internally in its implementation using the SQLJ runtime context. System.out.println( address.getAddress() ); } } finally { JDBCUtil.close ( rset, pstmt, connection ); } } } This concludes our discussion of using the SQLData interface. We will now discuss how to use the Oracle extension ORAData and ORADataFactory interfaces in JDBC programs. We will then compare the pros and cons of the SQLData and ORAData interfaces. The next section presents an overview of the interfaces ORAData and ORADataFactory.

Note When ASP.NET serves the page, it generates F# code using the F# CodeDom dynamic code generator.

Instead of using custom classes that implement the standard SQLData interface, we can use custom classes that implement the Oracle proprietary interfaces ORAData and ORADataFactory. The ORAData interface provides more flexibility as compared to the SQLData interface. For example, it lets you provide a mapping between Java object types and any SQL type supported by the oracle.sql package. Later, we will examine a detailed comparison between using the standard SQLData interface and using the ORAData and ORADataFactory interfaces. Let s start off with the definitions of ORAData and ORADataFactory: public interface ORAData { Datum toDatum (OracleConnection connection) throws SQLException; } public interface ORADataFactory { ORAData create (Datum datum, int sqlTypeCode) throws SQLException; }

Traditionally, an ASP .NET developer s concern regarding the application architecture ends at the database. Sure, you may need to decide between using stored procedures or queries, or you may need to work with the data administrator to define the data schemas, but the brunt of the design and the implementation is normally passed to those who live and breathe tables, views, stored procedures, triggers, and Transact-SQL (T-SQL). With the introduction of SQL Server 2005, however, come several new features that blur the sharp line between application and database concerns. Most notably, SQL Server 2005 provides a feature called Common Language Runtime (CLR) integration, which allows managed code to execute within the SQL Server 2005 process and interact directly with the data. Other new features of particular interest to application developers include Service Broker and XML as a native type. Although a detailed drill down of each of the features is beyond the scope of this book, this section provides an overview of each with the information you need to correctly position and leverage them in your architecture.