ASP.NET Web PDF Document Viewer/Editor Control Library

To insert a CLOB of zero length, we can use the function empty_clob() (or empty_blob() for BLOB; see the section Empty LOBs later in this chapter for more details). The following code updates our clob_col column to an empty_clob() and then verifies that the length of the CLOB value is now 0: benchmark@ORA10G> update clob_table set clob_col = empty_clob(); 1 row updated. benchmark@ORA10G> commit; Commit complete. benchmark@ORA10G> select length( clob_col) length_clob from clob_table; 0 Now for BLOBs. The following creates a blob_table table and inserts a row in it: benchmark@ORA10G> create table blob_table 2 ( 3 x varchar2(30), 4 id number, 5 blob_col blob 6 ); Table created. benchmark@ORA10G> insert into blob_table( blob_col) values ( '10101' ); 1 row created. However, you cannot do a select from the blob_table in SQL*Plus, as SQL*Plus is not equipped to display BLOB columns. benchmark@ORA10G> select blob_col from blob_table; SP2-0678: Column or attribute type can not be displayed by SQL*Plus We will cover how to overcome this in PL/SQL and JDBC in the upcoming sections.

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You already saw that datasets can be used to fetch and manipulate data in a disconnected way These datasets are managed by data adapters that handle the gory details of producing and issuing the appropriate SQL statements to the underlying database when fetching records or synchronizing the changes made to the dataset back to the database The main goal of a separate Data Access Layer (DAL) is to bridge the gap between two disparate domains: the database and your application logic Practically speaking, this means freeing you from having to write SQL code and mingling it with your application code O/R mappings use smart data objects that can load and persist record-level data, and underneath they use objects such as ADONET datasets that are filled and flushed on demand The tool we focus on in this section is SqlMetal, which computes the O/R mapping for LINQ, part of the .

asax, instead of relying on the template in ASP NET 20 When a globalasax is added to a Web project, the default template uses on inline script block: <%@ Application Language="C#" %> <script runat="server"> .. </script>.

In PL/SQL, the main mechanism of accessing and manipulating LOBs is through the DBMS_LOB package. We will briefly go through some examples in this section. You can explore this package functionality more fully by reading PL/SQL Packages and Types Reference (10g Release 1). Let s first look at the concepts of empty LOBs and temporary LOBs.

NET Framework 35 For example, to use SqlMetal to generate bindings for the Northwndmdf database, you can use this: sqlmetal /code:northwindcs /namespace:Nwind /server:\SQLExpress Northwndmdf This assumes you are running SQL Server Express on your machine as a named instance Further options are available when you run SqlMetal without parameters You may want to use the /code and /xml flags to specify a different output file of the object bindings and to create a schema definition, respectively The resulting code by default uses C#, which can be changed using the /language option You can easily add the generated mappings under a separate DLL project in your F# solution and reference it from your F# project For the remainder of this section, we will be using the generated data object layer for the classic Northwind database, as used by the F# LINQ samples in the F# distribution.

To revert to the code-behind model, remove the script block and add the Inherits attribute to the Application directive: <%@ Application Language="C#" Inherits='MyImpl' %> Now add a class file to the App_Code directory of your project and name it MyImpl (or whatever class you named with the Inherits attribute). Have this class use HttpApplication as its base class: public class MyImpl : HttpApplication { } This will leverage the ASP .NET 1.x model for the global.asax, with the exception that, by default, the class isn t compiled until runtime (as is the case for any class in the code directory). The type will still show up via IntelliSense in the IDE, and you can still code against it in a strongly typed manner. To trap HttpApplicaiton events, you now have two options. The aforementioned naming convention will work. Or you can add delegates to the base class events from the constructor. The following class traps both the BeginRequest and PreRequestHandlerExecute events: one by explicitly creating the trap; the other by using the naming convention. It also declares a static field that will be available throughout the application: using System; using System.Web; public class MyImpl : HttpApplication { public static string SomeStaic = "This is a static variable"; public MyImpl() { this.PreRequestHandlerExecute += new EventHandler(MyImpl_PreRequestHandlerExecute); } void Application_OnBeginRequest(object sender, EventArgs e) { Response.Write("Entering BeginRequest<BR>"); } void MyImpl_PreRequestHandlerExecute(object sender, EventArgs e) { Response.Write("Entering PreRequestHandlerExecute<BR>"); } }

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