1/36 Database Programming with Visual Basic.Net and MS Access 2009.4.29 IKE Lab. Yunho Song Database Management and Analysis

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Database Programming with Visual Basic .Net and MS Access

2009.4.29

IKE Lab.Yunho Song

Database Management and Analysis

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Contents

1. Installation

2. VB .NET and Database

1. The Database Wizard (Visual Studio users)

2. Write your own VB .NET database code

3. Learn about DataSets and Data Adaptors

4. Display the Data in the DataSet

5. Navigate a Database with VB .NET

6. How to Move through the Database

7. Add, Update and Delete Records

8. Add a New Record using VB .NET

9. Delete a Record using VB .NET

10. A VB .NET Database Project

1. Installation

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Installation

1. Installation


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1. Installation

Database Programming with Visual Basic .Net and MS Access Installation

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1. Installation

Database Programming with Visual Basic .Net and MS Access Installation

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1. Installation


First run - choose the default environment settings

Installation

2. VB .NET and Database

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VB .NET and Database

Let's make a start on our Database projectClick File > New Project from the menu barSelect Windows Application, and then give it the Name AddressBook. Click OKLocate the Solution Explorer on the right hand side


2.1. Database Wizard

Select Data Sources

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The Wizard display all your tables, fields and objects



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The Data Sources area displays information about your database



Click the plus symbol next to tblContacts

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To add a Field to your Form



A textbox and a label will be added

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Run your program by hitting the F5 key



Drag and Drop more Fields to your form

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The Connection ObjectWhat you need if you want to connect to a databaseOLE(Object Linking and Embedding)

•allow you to connect to data sources in general, and not just databases. You can

use it, for example, to connect to text files, SQL Server, email, and a whole lot more

Place a button on your form. Change the Name property to btnLoad

•Double click your button to open up the code window

• Add the following line:


2.2. Write your own Database code


Dim con As New OleDb.OleDbConnection

At the top of your code window, before Public Class Form 1, type the following:

Imports

System.Data

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Coding window will look like this

Get a pop up box from where you can select OleDbConnectionUse to connect to an Access database

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Setting a Connection StringThe technology is called the Provider; and you use "Data Source" to specify where

your database is

con.ConnectionString = "PROVIDER=Microsoft.Jet.OLEDB.4.0;Data Source = C:\AddressBook.mdb"

The first part specifies which provider technology we want to use to do the connecting

(JET) The second part, typed after a semi-colon, points to where the database isIn the above code, the database is on the C drive, in the root folder. The name of the

Access file we want to connect to is called AddressBook.mdb

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Opening the Connection Open method of the Connection Object:

Close method of the Connection Object:

con.Open( )MsgBox("A Connection to the Database is now open“)

con.Close()MsgBox("The Connection to the Database is now Closed“)

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Coding window

Test out our

code

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2.3. Data Sets and Data Adapters


Data SetsHidden from you, and just stored in memoryImagine a grid with rows and columns. Each imaginary row of the DataSet represents

a Row of information in your Access database. And each imaginary column represents a

Column of information in your Access database (called a Field in Access)

Data AdapterThe Connection Object and the DataSet can't see each otherThey need a go-between so that they can communicateThis go-between is called a Data AdapterThe Data Adapter contacts your Connection Object, and then executes a query that

you set up. The results of that query are then stored in the DataSet.

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Data Adapter and DataSet are objects

OleDb.OleDbDataAdapter

•Called da

•Hold a reference to the Data Adapter

da = New OleDb.OleDbDataAdapter(sql, con)

•creates a new Data Adapter object

•Need to put two things in the round brackets of the Object declaration

•SQL string (which we'll get to shortly), and connection object

•Connection Object is stored in the variable called con

Data Adaptor acting as a go-between for the Connection Object and the Data Set

Dim ds As New DataSetDim da As OleDb.OleDbDataAdapterda = New OleDb.OleDbDataAdapter(sql, con)

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Structured Query Language(SQL) A way to query and write to databases

•Hold a reference to the Data Adapter

To select just the first name and surname columns from our database

To SELECT all (*) the records from the table called tblContacts

Select * from Table_Name

SELECT tblContacts.FirstName, tblContacts.Surname FROM tblContacts

sql = "SELECT * FROM tblContacts”

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Structured Query Language(SQL)

Dim ds As New DataSetDim da As OleDb.OleDbDataAdapterDim sql As String

sql = "SELECT * FROM tblContacts"da = New OleDb.OleDbDataAdapter(sql, con)

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Filling the DataSetData Adapter can Fill a DataSet with records from a Table

The DataSet (ds) will now be filled with the records we selected from the table called

tblContactOne slight problem - nobody can see the data yet! We'll tackle that in the next part

da = New OleDb.OleDbDataAdapter(sql, con)da.Fill(ds, "AddressBook“)

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2.4. Displaying the Data in the DataSet


To display the records on a FormAdd two textboxes to your formChange the Name properties of your textboxes to txtFirstName and txtSurnameGo back to your code windowAdd the following two lines:

txtFirstName.Text = ds.Tables("AddressBook").Rows(0).Item(1)txtSurname.Text = ds.Tables("AddressBook").Rows(0).Item(2)

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2.5. Navigate a Database


To see a more practical exampleAdd two Textboxes. Change the Name properties to txtFirstName and txtSurnameAdd four Buttons. Change the Name and Text properties to these:

Button Name Button TextbtnNext

btnPreviousbtnFirstbtnLast

Next RecordPrevious RecordFirst RecordLast Record

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To see a more practical exampleAdd the following code to the Form1 Declarations area:

When the Form Loads, we can connect to our database, use the data Adaptor to grab

some records from the database and then put these records into the DataSet

•So in the Form1 Load Event, add the following code:

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To see a more practical exampleYou've met all the code before, except for these two lines:

In the MaxRows variable, we can store how many rows are in the DataSetGet how many rows are in DataSet with Rows.Count:

To navigate through the recordsUse inc variable. We'll either add 1 to it, or take 1 awayUse the variable for the Rows in the DataSetIt's better to do this in a Subroutine of ownSo add this Sub to code:

MaxRows = ds.Tables("AddressBook").Rows.Countinc = -1

Private Sub NavigateRecords()txtFirstName.Text = ds.Tables("AddressBook").Rows(inc).Item(1)txtSurname.Text = ds.Tables("AddressBook").Rows(inc).Item(2)End Sub

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The important part is Rows(inc). This moves us through the Rows in the

DataSet. Then placing the values into the two Textboxes

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Database Programming with Visual Basic .Net and MS Access VB .NET and Database

How to Move Forward One Record at a TimeDouble click your Next Record button to access the code

2.6. How to Move through the Database

Move Back One Record at a Timeto add to your btnPrevious:

If inc > 0 Theninc = inc - 1NavigateRecords()ElseIf inc = -1 ThenMsgBox("No Records Yet")ElseIf inc = 0 ThenMsgBox("First Record")End If

If inc <> MaxRows - 1 Theninc = inc + 1NavigateRecords()ElseMsgBox("No More Rows")End If

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Moving to the Last Record in the DataSetto add to your btnLast:

2.6. How to Move through the Database

If inc <> MaxRows - 1 Theninc = MaxRows - 1NavigateRecords()End If

Moving to the First Record in the DataSetto add to your btnFirst:

If inc <> 0 Theninc = 0NavigateRecords()End If

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DataSet is disconnected from the databaseNot adding the record to the database: adding it to the DataSet

How to add, delete, update new recordsAdd five more buttons to your form

2.7. Add, Update and Delete Records

Change the Name properties

btnAddNewbtnCommitbtnUpdatebtnDeletebtnClear

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Updating a RecordThe changes will just get made to the DataSetAdd the following code to btnUpdate:

2.7. Add, Update and Delete Records

ds.Tables("AddressBook").Rows(inc).Item(1) = txtFirstName.Textds.Tables("AddressBook").Rows(inc).Item(2) = txtSurname.Text

MsgBox("Data updated“)

"Changes are made to the DataSet, and NOT to the Database“To update the database, Add following code

Dim cb As New OleDb.OleDbCommandBuilder(da)

ds.Tables("AddressBook").Rows(inc).Item(1) = txtFirstName.Textds.Tables("AddressBook").Rows(inc).Item(2) = txtSurname.Text

da.Update(ds, "AddressBook")

MsgBox("Data updated“)

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Add a New RecordAdd New Record button:

2.8. How to Add a New Record

btnCommit.Enabled = TruebtnAddNew.Enabled = FalsebtnUpdate.Enabled = FalsebtnDelete.Enabled = False

txtFirstName.Clear()txtSurname.Clear()

The Clear/Cancel button can be used to switch it back on againAdd this code to btnClear:btnCommit.Enabled = FalsebtnAddNew.Enabled = TruebtnUpdate.Enabled = TruebtnDelete.Enabled = True

inc = 0NavigateRecords()

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To add a new record to the databaseAdd this code to btnCommit

2.8. How to Add a New Record

If inc <> -1 ThenDim cb As New OleDb.OleDbCommandBuilder(da)Dim dsNewRow As DataRow

dsNewRow = ds.Tables("AddressBook").NewRow()

dsNewRow.Item("FirstName") = txtFirstName.TextdsNewRow.Item("Surname") = txtSurname.Text

ds.Tables("AddressBook").Rows.Add(dsNewRow)

da.Update(ds, "AddressBook“)MsgBox("New Record added to the Database“)btnCommit.Enabled = FalsebtnAddNew.Enabled = TruebtnUpdate.Enabled = TruebtnDelete.Enabled = True

End If

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Deleting Records from a DatabaseAdd this code to btnDelete

2.8. Delete a Record from a Database

Dim cb As New OleDb.OleDbCommandBuilder(da)

ds.Tables("AddressBook").Rows(inc).Delete()MaxRows = MaxRows - 1

inc = 0NavigateRecords()da.Update(ds, "AddressBook“)

To display a message box asking users if they really want to delete this recordIf MessageBox.Show("Do you really want to Delete this Record?", _"Delete", MessageBoxButtons.YesNo, _MessageBoxIcon.Warning) = DialogResult.No Then

MsgBox("Operation Cancelled")Exit Sub

End If

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Thank You!!

Documents

1/36 Database Programming with Visual Basic.Net and MS Access 2009.4.29 IKE Lab. Yunho Song Database Management and Analysis