VB .NET Database Tools

ISYS 573

.Net Applications

OLE DBProvider

OLE DBData Source

OLE DBProvider

ODBC

ODBCData Source

SQL Server Data Source

SQL Server .Net Data Provider

OLE DB .Net Data Provider

ADO.Net

Steps to Retrieve Data

• Establishes a connection to the database.

• Executes commands against the database:– SQL Select, Insert, Update, Delete

• Store data results.

ADO.NET Objects

Data Set

.NET Applications

Data Reader

Command Object

Connection Object

Database

Adapter

ADO.NET Objects

• Connection Object: Represent a connection to the database.

• Command Object: The command object allows us to execute a SQL statement or a stored procedure.

• DataReader: It is a read-only and forward-only pointer into a table to retrieve records.

• DataSet Object: A DataSet object can hold several tables and relationships between tables.

• DataAdapter: This the object used to pass data between the database and the dataset.

How to create an ADO.Net object?

• Using Wizard– Data Form Wizard– Data Adapter Wizard

• Using code: – Example:– dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\

sales2k.mdb"

– dim objConn as new OledbConnection(strConn)

– objConn.open()

VB.NET Database Tools

• Database connection:– Tool/Connect to database

• Provider:MS Jet 4.0 OLE DB Provider

• Connection

• Server Explorer– Data connections:

• Right click and Add Connection

• Tables, Views

• Toolbox Data tab• Data Form Wizard

Data Form Wizard

• Creating a form with data-bound controls to display and update information in a dataset.

• Demo: Using Data Form Wizard to create a navigational form.– Project/Add Windows Form/Data Form Wizard– Set connection– Choose tables– Display records in grid or in text boxes.

Adapter & Dataset Context Menu

• Adapter:– Properties:

• Command objects

– Configure Adapter– Generate dataset– Preview data

• Dataset:– View Schema: Dataset/XML

Other Data Form Demos

• Display records in text boxes.

• Add /Modify/Delete records.

• Hierarchical forms:– Parent/Child relationship

Creating A Database Application Without Programming

• Creating a database application to display information and update database.

• A main form with buttons to open data forms:– DisplayInfo– Enter New– Modify– Exit

Data Adapter Wizard

• Configure Data Adapter and generating a dataset:– Drag OledbDataAdapter (or database’s table) to

the form.– Use the Data Adapter Wizard to configure the

Adapter.– Right Click the Adapter to preview data and

creating dataset.

• Bind the dataset to controls.

Data Binding

• Connect a control or property to one or more data elements.

Binding DataGrid

• From Server Explorer, drag the table from a database connection (or from Data tab, drag a oleDbAdapter) onto the form.

• Create dataset.• Drag DataGrid and set the DataSource and Data

Member property.• Use adapter’s Fill method to load the dataset.

– OleDbDataAdapter1.Fill(DataSet11)

Binding Text Box

• Data Bindings property:– Text: choose field

• Add navigation buttons:– The current record position within the dataset is

stored in a form’s BindingContext’s Position property. This position is zero based. Add one move to the next record, minus one move to the previous record.

MoveNext and MoveLast Example

• MoveNext:– Me.BindingContext(DataSet21, "customer").Position += 1

• MoveLast:– Me.BindingContext(DataSet21, "customer").Position =

Me.BindingContext(DataSet21, "customer").Count -1

• How to MovePrevious and MoveFirst?• Note: The Position property takes care of the end of file

automatically.

Introduction to ADO.Net Programming

Import NameSpace

• The Imports statement must appear before all other declarations in a file and cannot appear inside a class or module declaration.– Imports System.Data.OleDb– Public Class Form1

Connection Object

• Example:– dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\

sales2k.mdb"

– dim objConn as new OledbConnection(strConn)

– objConn.open()

• Basic Methods:– Open, Close

Command Object

• The command object allows us to execute a SQL statement.

• Properties:– CommandType: SQL or stored procedure– CommandText: SQL statement– Connection

• Basic Methods:– ExecuteReader: Creates a DataReader object that contains

the results of the query.– ExecuteNonQuery: Execute SQL’s INSERT, DELETE,

UPDATE statements.

DataReader Object

• It is read-only and forward-only cursor.

• Basic Methods:– Read: Reads the current record and advances

the pointer to the next record.– Close: Closes the dataReader.

ExecuteReader Example

dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb"

dim objConn as new OledbConnection(strConn)

dim strSQL as string = "select * from customer;"

dim objComm as new OledbCommand(strSQL,objConn)

dim Results as string

objConn.open()

dim objDataReader as oledbDataReader

objDataReader=objComm.executeReader()

Read Records in a DataReader

• dim Results as string• do while objDataReader.Read()=true

Results+=objDataReader("cid") + “ “ + objDataReader("Cname") + vbCrLF

• loop• Textbox1.text=Results

• Note: objDataReader.Item(0)• Note: objDataReader.Item(“cid”)

Add Items from a DataReader to a Listbox

Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb"

Dim objConn As New OleDbConnection(strConn)

Dim strSQL As String = "select cid from customer;"

Dim objComm As New OleDbCommand(strSQL, objConn)

objConn.Open()

Dim objDataReader As OleDbDataReader

objDataReader = objComm.ExecuteReader()

Do While objDataReader.Read() = True

LISTBOX1.Items.Add(objDataReader("cid"))

Loop

Display Selected Customer’s RecordPrivate Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged

Dim strSQL As String = "select * from customer where cid = '" & ListBox1.SelectedItem & "'"

Dim objComm As New OleDbCommand(strSQL, objConn)

objConn.Open()

Dim objDataReader As OleDbDataReader

objDataReader = objComm.ExecuteReader()

If objDataReader.Read = True Then

TextBox1.Text = objDataReader("Cname")

TextBox2.Text = objDataReader("City")

TextBox3.Text = objDataReader("rating")

Else

MessageBox.Show("record not found")

End If

objConn.Close()

End Sub

Insert a New Record Using ExecuteNonQuery

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb"

Dim objConn As New OleDbConnection(strConn)

Dim strSQLInsert As String

strSQLInsert = "Insert into Customer values ('"

strSQLInsert = strSQLInsert & TextBox1.Text & "','" & TextBox2.Text & "','"

strSQLInsert = strSQLInsert & TextBox3.Text & "','" & TextBox4.Text & "')"

Dim objComm As New OleDbCommand(strSQLInsert, objConn)

objConn.Open()

objComm.ExecuteNonQuery()

objConn.Close()

End Sub

Demo

• Create a project that do the following tasks:– Use a DataReader to retrieve customer IDs and

populate a listbox.– Select a new rating from radio buttons for the

selected customer.– Update customer’s rating using the

ExecuteNonQuery method of a Command object.

Declare OleDB objects and create listboxImports System.Data.OleDb

Public Class Form3

Inherits System.Windows.Forms.Form

Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb"

Dim objConn As New OleDbConnection(strConn)

Dim strSQL As String = "select cid from customer;"

Dim objComm As New OleDbCommand(strSQL, objConn)

Private Sub Form3_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

objConn.Open()

Dim objDataReader As OleDbDataReader

objDataReader = objComm.ExecuteReader()

Do While objDataReader.Read() = True

ListBox1.Items.Add(objDataReader("cid"))

Loop

objConn.Close()

End Sub

Update customer ratingPrivate Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

objConn.Open()

Dim newRating As String

If RadioButton1.Checked = True Then

newRating = "A"

ElseIf RadioButton2.Checked Then

newRating = "B"

Else

newRating = "C"

End If

Dim strSQLUpd As String = "Update customer set rating = '" & newRating & "'"

strSQLUpd = strSQLUpd & " where cid='" & ListBox1.SelectedItem & "'"

Dim objCommUpd As New OleDbCommand(strSQLUpd, objConn)

objCommUpd.ExecuteNonQuery()

objConn.Close()

End Sub

Testing for Null

If objDataReader.Read = True Then

If IsDBNull(objDataReader("custCount")) Then

TextBox1.Text = 0

Else

TextBox1.Text = objDataReader("custCount").ToString

End If

End If

Note: Difference between Nothing and Null?

Null Value ExamplePrivate Sub ListBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ListBox1.SelectedIndexChanged

Dim strConn As String = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb"

Dim objConn As New OleDbConnection(strConn)

Dim strSQL As String = "select * from customer where cid = '" & ListBox1.SelectedItem & "'"

Dim objComm As New OleDbCommand(strSQL, objConn)

objConn.Open()

Dim objDataReader As OleDbDataReader

objDataReader = objComm.ExecuteReader()

objDataReader.Read()

TextBox1.Text = objDataReader("Cname")

TextBox2.Text = objDataReader("rating") ‘ Statement won’t work if Rating is null in database

End Sub

Setting a Field to Null with a Update Statement

Dim strSQLUpd As String = "Update Customer Set Rating = null Where cid = '" & ListBox1.SelectedItem & "'"