1. Chapter 10 Accessing Database Files
Programming In
Visual Basic .NET

2. 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)
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

3. ADO.NET
Data is stored and transferred in Extensible Markup Language (XML)
Allows access to database data in many formats
Basic types of providers
OleDb, SQLClient for SQL Server, Odbc and Oracle
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

4. Database Terminology Databases Tables Relational database
Records (rows)
Fields (columns)
Key field (unique to each record)
Relational database
Multiple tables
Relationships between the tables
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

5. XML Data Industry-standard format for storing and transferring data
Specifications at World Wide Web Consortium (W3C)
The XML needed for accessing databases will be automatically generated for you in Visual Basic
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

6. XML Data (continued)
Data stored in XML are all text, identified by tags
XML files can be edited by any text editor, such as Notepad
Tags
Used for identification, similar to HTML
Not predefined like HTML tags
Can identify database fields by name
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

7. XML Data (continued) XML Data File XML Schema File (.xsd file)
Contains actual data
XML Schema File (.xsd file)
Contains descriptions for
Fields
Data Types
Constraints, such as required fields
View .xsd file in Solution Explorer
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

8. 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
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

9. Using ADO.NET and Visual Basic (continued)
Connection
Establishes a link to a data source, a specific file and/or server
Data Adapter
Handles retrieving and updating the data
Dataset
Contains actual data, may come from multiple connections and/or multiple data adapters
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

10. Steps to Display Data in Bound Controls on a Form
Source
Connection
Adapter
Dataset
Web
Form
Windows
Specific file
Connection Object
Handles data transfer and provides data for dataset; uses SQL
Actual data, can contain multiple tables and relationships
Data display on the form in bound controls
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

11. Connections
Establishes a link from specific file or database to program
ADO.NET provides four types
OleDBConnection
SqlConnection
OdbcConnection
OracleConnection
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

12. Connections (continued)
Creating a new connection
Data controls in the Toolbox
Use Server Explorer to manage connections
No matter which method above is used to begin the connection, the Data Link Properties dialog appears for you to complete the task
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

13. Creating a Connection from Server Explorer
Click Connect to Database button OR
Right-click Data Connections, select Add Connection
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

14. Data Link Properties Dialog
Used to define Connection's
OLE DB Provider
Database Filename
Can test if connection succeeded
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

15. Connections in Server Explorer
Shows connections for all projects
Same connection can be used for multiple projects
Expand connection node to view tables and fields
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

16. Data Adapters
Does all the work of passing data back and forth between a data source and a program
Data does not have to be from a database
Data can be text file, object, or even an array
Add data adapter
Drag table name from Server Explorer to form
Ctrl + click field names and drag as a group to the form
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

17. 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
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

18. Datasets (continued) To define a dataset
Select data adapter component
Right-click on the adapter and select Generate Dataset
Name the dataset in the Generate Dataset dialog box
Write code to fill the dataset (opens the connection to the data source and retrieves data into the dataset)
Any controls bound to the dataset will automatically fill with data
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

19. Data Passes from Data Source to Dataset to User Interface
Data Object
(Class)
Windows
Forms
Web
Data
Adapter
Presentation Tier
Business Tier
Data Tier
Dataset
Source
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

20. The Fill Method
Execute Fill method of Data Adapter at run time to fill the dataset
Usually coded in Form_Load (or Page_Load for Web projects)
General Form
Example
DataAdapterName.Fill(DataSetName)
booksDataAdapter.Fill(BooksDataset1)
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

21. Binding Data to Controls
Set properties of the controls
To bind data to a grid, set
DataSource property
Data Member property
To bind individual fields to controls (such as labels and text boxes)
Set DataBindings property
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

22. Creating a Bound DataGrid Control (pages 391-394)
Steps
Set up the Connection
Add the Connection and Data Adapter to the Form
Rename Connection and Data Adapter
Generate a Dataset
Add a Data Grid to the Form and set DataSource and DataMember properties
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

23. Creating a Bound DataGrid Control (continued)
Write the Code
Windows Form - Form_Load booksDataAdapter.Fill(BooksDataset1)
Web Form - Page_Load booksDataAdapter.Fill(BooksDataset1) booksDataGrid.DataBind( )
Run the Project
Modify the Grid Format
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

24. Displaying a Data Preview
Allows you to see what your data looks like while you are designing the user interface
Right-click DataAdapter control, select Preview Data
In the dialog box verify that the correct DataAdapter displays in the list
Click Fill Dataset, resize columns and scroll to see all data
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

25. Displaying a Data Preview (continued)
Click to Display the data
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

26. Binding Data Complex Data Binding Simple Data Binding
Binds more than one data element to a single control
Used for DataGrids, and List or Combo Boxes
Set DataSource and DataMember properties (may need additional)
Simple Data Binding
Connects one control to one data element through the Data Bindings property
Use for TextBoxes and Labels (or any other control that has a Data Bindings property)
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

27. Selecting Records from a Combo Box
Allows user to select records to view or update
Windows Forms
Use ListBox or ComboBox
Web Forms
Use ListBox or DropDownList
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

28. Filling a List - Windows Forms
Set ListBox or ComboBox Properties
DataSource to DataSet name
DisplayMember to table name.field name
Use Fill method to populate list with data
' Fill the dataset for the list box. BooksDataAdapter.Fill(BooksDataset1)
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

29. Binding a Single Data Field
To bind data to a single control set the DataBindings property
Expand DataBindings property and choose the Text property
Expand the Dataset to reveal a list of fields
Set the DataBindings Text property to the correct field
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

30. Binding a Single Data Field (continued)
Bind a Label control’s Text property to a single field in a dataset
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

31. Sorting the List Data
Sort records using the data adapter’s SQL SELECT statement
Select the data adapter, choose Data/Configure Data Adapter
Navigate through the Wizard to the SQL statement page
Choose “Ascending” in the Sort Type cell of the Query Builder
Right-click the data adapter, select Generate Dataset and select the existing dataset name
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

32. Sorting the List Data (continued)
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

33. Selecting Records Using Web Forms
Set up connection, data adapter and dataset same as for Windows applications
Need to modify program logic for the Web due to security and because web pages are Stateless
Stateless means that each time a page displays it is a new fresh page
Page_Load event occurs for every round trip to the server
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

34. Filling a List – Web Forms
Postback, round trip to the server, occurs each time user makes a selection
After Postback, web page redisplays, Page_Load event occurs
Modify logic in Page_Load to use selection made by user
Use Me.DataBind( ) statement to bind all controls on page at once
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

35. Setting the List Properties
Properties to set for the Web version of DropDownList control
DataSource property to the Dataset
DataMember to the table name
DataTextfield to name of field to display in list
AutoPostBack property set to True to respond when a user selects from the list
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

36. Retrieving the Selected Record
In a Web application, the dataset is created on the server, only one pageful of data is sent to the client
When a user makes a selection from a list, it makes sense to retrieve only the selected record, not the entire table
Use a parameterized query to create a dataset with only the selected record
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

37. Retrieving the Selected Record (continued)
A Web selection application will have two data adapters
One selects data to fill a drop-down list
One selects a single record to display
An SQL SELECT statement to select a particular record requires a WHERE clause
Use a question mark in place of an actual value and supply the value as a parameter in code
This type of query is called a parameterized query
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

38. Query Builder - Parameterized Query
Where (Title = ?)
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

39. Displaying the Data for a Selected Item
Supply value to be used for a Parameterized Query at run time
TextBox
Check for an empty dataset after the Fill method
List box selection
Write code in the SelectedIndexChanged Event
Specify the parameter value using the Parameters collection of the data adapter’s SelectCommand property
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

40. Displaying the Data for a Selected Item – Code Example
Private Sub titleDropDownList_SelectedIndexChanged(ByVal _
sender As System.Object, ByVal e As System.EventArgs) _
Handles titleDropDownList.SelectedIndexChanged
' Retrieve the record matching the selection.
If titleDropDownList.SelectedIndex <> -1 Then
BooksDataset1.Clear( )
booksDataAdapter.SelectCommand.Parameters("Title").Value _
= titleDropDownList.SelectedItem.Text
booksDataAdapter.Fill(BooksDataset1)
ISBNLabel.DataBind( )
authorLabel.DataBind( )
End If
End Sub
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.

41. Making a Database Project Portable
You must move database AND
Create Connection on new computer
Configure DataAdapter
For Web projects, also create virtual directory
Less problems if the database is stored in the bin folder of the project
Do not include path in the data adapter’s ConnectionString property
© 2005 by The McGraw-Hill Companies, Inc. All rights reserved.