aslkjdhfalskhjfgalsdkfhalskdhjfglaskdhjflaskdhjfglaksjdhflakshflaksdhjfglaksjhflaksjhf Brief description on how to navigate within this presentation (ppt) The first time a Key Term from the chapter is used in the ppt it will display in blue Gold colored text boxes display coding examples Slides will be numbered (# of #) when multiple slides on same topic (Slide title) Speaker notes are included where appropriate for slides (*)Denotes either a comment for page reference to textbook or slide reference in ppt

Accessing Database Files 10 Chapter Accessing Database Files McGraw-Hill © 2006 The McGraw-Hill Companies, Inc. All rights reserved.

Objectives Use database terminology correctly Create Windows and Web projects that display database data Display data in a DataGridView control Bind data to text boxes and labels Allow the user to select from a combo box or list box and display the corresponding record in data-bound controls

Visual Basic and Database Files VB projects can display and update the data from database files VB .NET uses ADO.NET for database access ADO.NET is the next generation of database technology, based on Microsoft's previous version, ActiveX Data Objects (ADO) An advantage of ADO.Net is that information is stored and transferred in Extensivle Markup Language (XML) ADO.NET allows the access to database data in many formats including: OleDb, SQLClient for SQL Server (Microsoft’s proprietary DBMS), Odbc, and Oracle. Data from sources such as Access, Oracle, Sybase or DB2 can be obtained when using OleDb

Database Terminology Databases Tables – can be viewed like a spreadsheet Records (rows) – data for one item, person, transaction Fields (columns) – stores a different element of data Key field (unique to each record) Relational database Multiple tables Relationships between the tables To use database file the standard terminology of relational databases needs to be understood.

Database Table Example

XML Data (1 of 2) Industry-standard format for storing and transferring data The XML needed for accessing databases will be automatically generated in Visual Basic Data stored in XML is text, identified by tags-similar to HTML tags and can be edited by any text editor program Tags in XML are not predefined as they are in HTML Tags can identify fields by name *Specifications at http://www.w3.org/XML, World Wide Web Consortium (W3C)

XML Data (2 of 2) In addition to an XML data file there is normally an XML schema file Schema describes the fields, data types, and any constraints, such as required fields ADO.NET validates the data against the schema and checks for constraint violations Schema is defined with XML tags and can be viewed/edited in a text editor ADO.NET can treat the XML data as objects-allows the IntelliSense feature of the VS.NET environment to provide information to the programmer Data executes faster

Using ADO.NET and Visual Basic Can display data from a database on Windows Form Web Form Add controls to form and bind data to them Label, TextBox Special controls designed just for data such as DataGrid, DataList Remember that controls for a Windows application are different from controls for a Web application and have different properties and events

The DataGrid View Control The DataGridView control is bound to a table in a dataset. The data fields display automatically in the cells of the grid.

Data Access in Visual Studio 2005 Allows an easy way to create data-bound controls on a form Can drag tables and fields from the window onto a form to automatically create controls that are bound to the data Data can be displayed in grids or individual fields-referred to as details Can drag a field from the Data Sources window and drop it on an existing control-causes data binding to be set up automatically An .xsd file and the schema is added to the Server Explorer window; Binding Source, Table Adapter, and Data Set objects are added to the form’s component tray To set up data access in VB several classes and objects are used

Overview of Database Objects Binding Source Establishes a link to the actual data; a specific file and/or server Table Adapter Handles retrieving and updating the data Generates SQL statement that are used to access or update data Dataset Contains actual data, may come from multiple connections and/or multiple data adapters

Steps to Display Data in Bound Controls on a Form

Binding Sources Object establishes a link from a specific file or database to the program Can you a wizard to automatically create Binding Source objects –OR— Add new Binding Source objects using the Data Sources window or the Data menu

Table Adapters Does all the work of passing data back and forth between a data source (the binding source) and a program (the dataset) Data does not have to be from a database Data can be text file, object, or an array Transfers data to and from via XML

Datasets Temporary set of data stored in memory In ADO.NET datasets are disconnected; the copy of data kept in memory does not keep an active connection to the data source Dataset may contain multiple tables and relationships Any controls bound to the dataset will automatically fill with data

The Smart Tag Smart Tags are used for many functions including: Selecting a data source Editing properties of grid columns AutoFormat the grid Preview data Preview helps users do a better job of designing output Selecting AutoFormat allows the user to choose from many predefined format *The next slide displays the grid with a predefined format

Grid with Pre-Defined AutoFormat Predefined formats can be applied from the AutoFormat item on the smart tag.

The Database Schema File When a new data source is added to a project, a file .xsd is added to the Solution Explorer-the XML schema definition XML file contains the description and properties of the data The schema shows the names of the table(s) and fields, the primary keys for each table and the relationships among the tables At the bottom of the schema appears the TableAdapter for the table which handles different methods for the table

.XSD File The .xsd file holds the schema of the database, where table elements, relationships, and keys can be viewed and modified

Binding Individual Data Fields Table fields from the dataset can be bound to many types of controls such as labels, text boxes, combo boxes, and check boxes Controls that are connected to fields are bound controls or data-bound controls Easiest way to create bound controls is to use the automatic binding feature of the Data Source window Creates individual text box controls for each field of data and navigation control allowing the user to more from one record to another *The next slide displays a form with data0bound text boxes

Data-Bound Text Boxes -Example Each text box or check box is bound to one field from the table. As the user clicks the navigation buttons, all controls change to display the data for the next record

The Data Sources Window This window is used to add a new data source by using the Data Source Configuration Wizard Click the table name to make a drop-down list available to view Details The table’s icon changes to match the view

Selecting Records from a List Allows user to select records to display from a list Fill a ListBox or ComboBox with values from the database –OR— Display the information in a drop-down list and allow the user to make a selection; the corresponding data elements fill remaining fields

Selecting Fields from the Table Select individual fields when creating the new data source –OR– after creating the data source When creating the data source choose the AddNewData Source option and follow the Configuration Wizard; expand the Tables node and palce a check mark on the desired fields To modify after creating, select the dataset and use the Configuration Wizard and make the field selections from the Wizard *The next slide displays the Data Source Configuration Wizard

Data Source Configuration Wizard Select only the fields that are to be included in the Data Source Configuration Wizard

Sorting the List Data Sort records in a query that selects data for the dataset SQL SELECT statement is generated automatically by the designer; can be modified Use the Solutions Explorer and the schema file (.xsd extension) and the Property button (…) Choose “Ascending” in the Sort Type cell of the Query Builder Execute the query to preview the output You cannot sort bound data in a combo box or list box using the Sorted property of the control *The next slide displays the dialog boxes to sort data

Sorting Data Click the Fill,GetData() entry in the dataset schema to display the properties of the Fill command in the Properties window. Select Ascending for the Sort Type to sort the data by the Title field. The SQL statement changes to include an ORDER BY clause

Choosing the Control Type for Fields Dragging a Details view to a form displays text boxes for the default text fields Click a field name and choose a control type in the Data Sources window You can choose the control type for all controls and then drag the table to the form to create the Details view

Selecting Records Using Web Forms Web controls are much different from Windows controls Additional security issues for Web-based database applications Web database applications operate differently than Windows applications due to web pages in a client/server environment Web pages are stateless—each time a page displays it is a new page Each time the user makes a selection from a list a postback occurs and the Web page redisplays with only the selected data When you write database programs for the Web instead of Windows, you have a few more considerations—setting up data sources and bind to controls—but the Web controls are considerably different from their Windows counterpart

Security in Web Database Applications Security is much tighter for Web database applications than for Windows applications Require user authentication if setting up a Web application that displays or allows modification to data Visual Studio 2005 integrates security features which are general strict by default Visual Studio 2005 ensures that data will be secure unless the user takes steps to unprotect the files

Moving Database Projects Improvement from previous versions of VB.NET Project needs to be closed in the IDE Copy the complete folder from one computer or location to another For Web projects, open the IDE, select Open Web Site and browse to the folder You should be able to move the database projects in this chapter to another computer, open them in the IDE, and edit and/or run the applications. This is a huge improvement over earlier versions of VB .NET.