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VISUAL BASIC ²⁰¹⁰

Coding Briefs

DATA ACCESS

In today’s high-tech, information driven world, the security of personal data is vital. We have all heard the horror stories of personal data being compromised from companies, both large and small.

The data access framework that we will develop in Coding Briefs will allow us to create datasets, execute queries, and select data in a secure, managed process.

This framework will provide a solid foundation for managing secure data access through stored procedures, allowing us to select, insert, update, and delete records from a SQL Server database. We will have access to parameterized queries and will develop an automated process for discovering stored procedure parameters.

The major areas that we will address in this brief are as follows:

•Discussing the Data Access Framework (DAL)

•Importing Libraries and Declaring Values

•Managing the Database Connections

•Selecting Records

•Manipulating Data

•Preparing the Select and Execute Methods

•Working with Parameters

•Testing the Data Access Framework

And, as a bonus, two complete sample applications have been added; one for Windows, and one in ASP .Net, that will test all of the features on the data access framework.

Defining the Data Access Framework

The data access framework in this brief needs to be able to store and retrieve all of the data that is necessary for our data centric applications to perform as they are designed to. In order to accomplish this data access task, we will rely on the following tools and practices:

•All of the data for Coding Briefs will be stored in a SQL Server 2008 database

•All of the business rules will be managed in a series of Business Object classes

•We will have a central data access layer (DAL) that can be called from any form, class, or module in Windows and ASPX applications

•All database interaction will employ stored procedures

With the Microsoft tools that are available to us, and a little ingenuity, we can design and develop a very robust Data Access Framework that can be used, not only for Coding Briefs, but for most other applications that we develop in the future

In the next section, we design the data access framework.

Designing the Data Access Framework

For a data access framework to be useful and effective, it must be easy for the developer to use, and flexible enough to accommodate all types of data access requests. The data access framework in Coding Briefs solves both those important issues.

Figure 1: Basic Data Access Flow, as shown below, depicts the basic flow of the data access framework.

Figure 1: Basic Data Access Flow

The DAL of Coding Briefs Data Access Framework is designed to perform two major tasks:

•Select records

•Execute actions against records

Selecting Records

A well designed DAL will allow the developer to select records and return them in a container, such as a DataSet, or a SqlDataReader. The DAL that we will develop for Coding Briefs is no exception. It will allow us to select records and return the selection as a DataSet or a SqlDataReader.

Executing Records

Coding Briefs’ DAL provides functionality to execute an action type stored procedure. Action stored procedures are those that insert records, update records, or delete records from a database. For execution, the number of affected row is returned. So now that we have a high-level view of the functionality of the DAL, it is time to jump in and get started developing it.

In the next section, we will get the sample applications up and running.