MELJUN CORTES Vb.net ado.net part_ii

Visual Basic .NET Programming

DataSet DataSet DataSet DataSet ObjectObjectObjectObject

� a disconnected, memory resident cache of

data

� reads the database and creates an in-

memory copy of that part of that database

that the program needs

ADO.NET * Property of STIPage 1 of 26

� contains DataTables, DataRelation and

Constraints objects


PopulatingPopulatingPopulatingPopulatingDataSetsDataSetsDataSetsDataSets

� done at runtime

� use DataAdapter to access data

� Example:

Private conServer As

SqlClient.SqlConnection

Public Sub Form1_Load(ByVal

sender As System.Object,


sender As System.Object,

ByVal e As System.EventArgs)

Handles MyBase.Load

conserver = New

SqlClient.SqlConnection()

Dim strConnection As String =

“Integrated Security=True;Data

Source=Localhost;Initial

Catalog=Books;”

conServer.ConnectionString =

strConnection

conserver.Open()

End Sub


PopulatingPopulatingPopulatingPopulatingDataSetsDataSetsDataSetsDataSets

� Example: (con’t)

Private Sub Button1_Click ByVal sender

As System.Object, ByVal e As

System.EventArgs) Handles

Button1.Click

Dim adaptSQL As

SqlClient.SqlDataAdapter(“Select



count(*) from Catalogue”,

conserver)

‘the code that will fill the DataSet

Dim datBooks As New DataSet()

adaptSQL.Fill(datBooks, “MyTable”)

‘manipulate data locally using

DataSet

adaptSQL.Update(datBooks, “MyTable”)

End Sub


Relationships Relationships Relationships Relationships in DataSetin DataSetin DataSetin DataSet

� DataRelation object

� allows tables to provide relationship with each

other

� contains an array of DataColumn objects that

define the parent column, primary key and child

column or foreign key in the relationship

� Example:

Private Sub Button1_Click ByVal sender As

System.Object, ByVal e As



System.EventArgs) Handles Button1.Click

Dim adaptSQL As SqlClient.SqlDataAdapter


adaptSql = New

SqlClient.SqlDataAdapter(“Select ISDN,

title, author, publisher from

Catalogue”, conServer)

adaptSQL.Fill(datBooks, “MyTable1”)

adaptSql = New

SqlClient.SqlDataAdapter(“Select ISDN,

name, address from Publisher”,

conServer)

adaptSQL.Fill(datBooks, “MyTable2”)


Relationships in Relationships in Relationships in Relationships in DataSetDataSetDataSetDataSet

� Example: (con’t)

‘the code that provides the

relationship

Dim relBooksTitile As New

DataRelation(“BooksTitles”,

datBooks.Tables(“MyTable1”).Columns(

“ISDN”),


“ISDN”),


“ISDN”))

datBooks.Relations.Add(relBooksTitle)

End Sub


Accessing Accessing Accessing Accessing Related DataRelated DataRelated DataRelated Data

� GetChildRows method

� used to access related records in a

different table

� Example

Dim BookRow, PubRow As DataRow

Dim TitleRows() As DataRow ‘ Array


Dim TitleRows() As DataRow ‘ Array

of DataRow objects

BookRow =

datBooks.Tables(“MyTable1”).Rows

(0)

TitleRows =

BookRow.GetChildRows(“BooksTitle

s”)

For Each PubRow In TitleRows

ListBox1.Items.Add(PubRow(“title

”).ToString)

Next


Creating Creating Creating Creating ConstraintsConstraintsConstraintsConstraints

� Constraint

� a rule used to maintain the integrity of the

data in the DataTable

� Types of constraint classes to DataColumns:

� ForeignKeyConstraint

� UniqueConstraint


� ForeignKeyConstraint

� controls what happens to a child row when a

parent row is updated or deleted

Cascade Deletes or updates any child

records based on the parent

record.

SetNull Sets related values to DB Null.

SetDefault Sets related values to their

defaults.

None Does not affect related rows.



� ForeignKeyConstraint Example:

Dim colParent As DataColumn

Dim colChild As DataColumn

Dim fkcBooksTitles As

ForeignKeyConstraint

colParent =


“ISDN”)


colChild =


“ISDN”)

fkcBooksTitles = New

ForeignKeyConstraint(“BooksTitlesFKC

onstraint”, colParent, colChild)

fkcBooksTitles.DeleteRule =

Rule.SetNull

fkcBooksTitles.UpdateRule =

Rule.Cascade

datBooks.Tables(“titles”).Constraints.A

dd(fkcBooksTtiles)

datBooks.EnforceConstraints = True



� UniqueConstraint

� can be added to one column or to an array

of columns

� checks if the values in the columns are

unique

� UniqueConstraint Example


Dim ucTitles As New

UniqueConstraint(“UniqueTitles”,

datBooks.Tables(“titles”).Column

s(“title”))

datBooks.EnforceConstraints = True


Using Existing Using Existing Using Existing Using Existing ConstraintsConstraintsConstraintsConstraints

� FillSchema method

� used to copy constraint information into a

DataSet

� Example:

adaptSQL = New



ISDN, title, author, publisher

from Catalogue”, conServer)

adaptSQL.FillSchema(datBooks,

schematype.Source, “Titles”)

adaptSQL.Fill(datBooks, “Titles”)

‘edit some data

adaptSQL.Fill(datBooks, “Titles”)


Updating Data Updating Data Updating Data Updating Data in the DataSetin the DataSetin the DataSetin the DataSet

� Adding Rows

� instantiate DataRow object by issuing the

NewRow method of the DataTable

� populate the columns with data

� call the Add method of the DataRows

collection passing the DataRow object

� Example:


� Example:

Dim newDataRow As DataRow =

datBooks.Tables(“Titles”).NewRow

newDataRow(“title”) = “New York”

newDataRow(“type”) = “business”

datBooks.Tables(“Titles”.Rows.Add(n

ewDataRow)



� Editing existing rows

� Call the BeginEdit method of the row.

� Change the data in the columns.

� Call the EndEdit or CancelEdit to

accept or reject the changes.

� Example:


� Example:

Dim editDataRow As DataRow =

datBooks.Tables(“Titles”).Rows(0

)

editDataRow.BeginEdit()

editdataRow(“Title”) =

editDataRow(“Title”).ToString &

“ 1”

editDataRow.EndEdit()



� Deleting Data

� Remove method

� Delete method

� Remove method Example

Dim delRow As DataRow =

datBooks.Tables(“Titles”).Rows(0


)

datBooks.Tables(“Titles”).Rows.Rem

ove(delRow)

� Delete method Example

Dim delRow As DataRow =

datBooks.Tables(“Titles”).Rows(0)

datBooks.Tables(“Titles”).Rows.Delete(delRo

w)



� To commit deletion invoke AcceptChanges

of the DataSet:

� datBooks.AcceptChanges()

� To undo deletion invoke RejectChanges of

the DataSet:


the DataSet:

� datBooks.RejectChanges()


Designing Designing Designing Designing DataSetsDataSetsDataSetsDataSets

� Connection Wizard

� Tools > Connect to Database


� click the Change button to select the data

source



� select a data source then click OK


� on the Data source specification section, click

the Use user or system data source namethen select the MS Access Database

� click OK. Select the Access database file and

then click OK

� open the Server Explorer panel to see the

connection that appears under the Data

Connections



� DataAdapter Configuration Wizard

� can be used with an existing database

connection

� Adding DataAdapter to Toolbox

� right-click Data from the Toolbox then

click Choose Items


� tick on a data adapter

• (i.e. OleDbDataAdapter)

� click OK


Data Binding in Data Binding in Data Binding in Data Binding in Windows FormsWindows FormsWindows FormsWindows Forms

� Data binding

� used to customize the appearance of the

forms

� Types of binding

� Simple Binding

• used to link a control to a single field in a


• used to link a control to a single field in a

DataSet

� Complex Binding

• used to link multiple fields in a DataSet



� Simple Binding Example:Private conServer As SqlClient.SqlConnection

Public Sub Form1_Load(ByVal sender As


System.EventArgs) Handles MyBase.Load

conserver = New SqlClient.SqlConnection()

Dim strConnection As String = “Integrated

Security=True;Data

Source=Localhost;Initial Catalog=Books;”

conServer.ConnectionString = strConnection



conserver.Open()

End Sub




Dim adaptSQL As

SqlClient.SqlDataAdapter(“Select title,

author from Catalogue”, conserver)



adaptSQL.Fill(datBooks, “Catalogue”)

TextBox1.DataBindings.Add(“Text”,

datBooks.Tables(“Catalogue”), “title”)

TextBox2.DataBindings.Add(“Text”,

datBooks.Tables(“Catalogue”), “author”)

End Sub



� Complex Binding Example:

Private conServer As SqlClient.SqlConnection

Public Sub Form1_Load(ByVal sender As


System.EventArgs) Handles MyBase.Load

conserver = New SqlClient.SqlConnection()

Dim strConnection As String = “Integrated

Security=True;Data





conserver.Open()

End Sub




Dim adaptSQL As

SqlClient.SqlDataAdapter(“Select title,

author from Catalogue”, conserver)



adaptSQL.Fill(datBooks, “Catalogue”)

DataGrid1.DataSource =

datBooks.Tables(“Catalogue”)

End Sub


Demonstration: How to Demonstration: How to Demonstration: How to Demonstration: How to Create a Data SourceCreate a Data SourceCreate a Data SourceCreate a Data Source

� File > New Project and name it as

MyDataSource then click OK

� select the ToolBox tab

� select the OleDbDataAdapter from the

ToolBox and drop it onto the form


� click New Connection



� click the Change button

� select Microsoft Access Database File


� select Microsoft Access Database File then click OK



� click the Browse button to locate

StudentDB access database then click OK

� click Next


� select Use SQL Statements then click Next



� click the Query Builder button


� select the Student table then click Addand Close button



� tick the (All Columns) checkbox

� click the OK button to save and close the

window

SELECT student.*

FROM student

� click Next then the Finish button


� click Next then the Finish button

� right-click the OleDbDataAdapter1 and

select Generate DataSet then click the

OK button

� right-click on the OleDbDataAdapter1again then choose Preview Data



� click the Preview button to view data in

then click the Close button

� OleDbDataAdapter, OleDbConnection, and

dataset are now created. This new

dataset can be used in any .Net control of

your choice


your choice

Technology

MELJUN CORTES Vb.net ado.net part_ii