Introduction to ADO.Net, VB.Net Database Tools and Data Binding

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Steps to Retrieve Data

• Establishes a connection to the database.

• Executes commands against the database.

• Store data results.

A Simplified View of ADO.Net Objects

Ado.Net

Data Provider

Connection

Adapter

Command

Reader

DatasetData Consumer

WinForm

WebForm

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.

Data Providers

• ODBC Provider– Open Database Connectivity

• A driver manager• Used for relational databases

• OLE DB Provider– OLE DB interfaces provide applications with uniform

access to data stored in diverse information sources, or data stores.

– Access

• SQL Server Provider• Oracle Provider

Using ODBC

• Windows XP: • Control Panel /Administrative Tools/DataSource(ODBC)

• Three types of data source names– User DSN: usable only by you and only on the machine

currently using.

– System DSN: Any one using the machine can use.

– File DSN: Can be copied and used by other computers with the same driver installed.

VB.NET Database Tools

• Database connection:– Tools/Connect to database

• Data Source

• Server Explorer– Data connections: Right click data connection

• Add Connection– Tables, Views

• Create new SQL Server Database

• Toolbox:Data tab• Data/Add New Data Source

Creating SQL Server Database

• From Server Explorer, right click data connection and choose:

• Create new SQL Server Database

• Server name: – LocalServerName\SQLExpress

• Add new table: Right click Tables and choose Add New Table

• Add rows: Right click the table name and choose Show table data.

How to create an ADO.Net object?

• Automatically generated when creating data bound form.– Form wizard

• Using 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()

Data Binding

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

• Simple binding: Use simple binding to display a field value in controls that show Data Bindings in the property window, such as text box or label.

• Complex binding: Use complex binding to bind more than one field to controls such as DataGrid and list box. Use the control’s Data Source and Data Member to bind the data.

Creating Data Bound Form

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

• Demo: – Add data source.

– Click the dropdown list next to the table’s name:• Datagrid view

• Details

– Drag the table to form.

Items Added to the Form• Connection• Table Adapter: click smart tag

– Add query– Preview data

• Dataset:– Edit in dataset designer

• Binding Source– Add query: Add a new tool strip.– Preview data

• Binding navigator• Code view: Form load event

– Me.CUSTOMERTableAdapter.Fill(Me.Sales2KDataSet.CUSTOMER)

Other Data Form Demos

• DataGrid View• Add /Modify/Delete records.• Read only form:

– Delete AddNew, Delete, Save buttons from navigator bar.

• Hierarchical forms:– Dataset has Tables collection and Relations collection.

• Parent/Child relation

– Drag the parent table and the child table to the form. Parent table uses detail view and child table uses dataGrid view

– Change dataGrid’s DataSource property to the relation.

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:– From the Data tab of the ToolBox, Drag

OledbDataAdapter to the form.– Use the Data Adapter Wizard to configure the Adapter.– Right Click the Adapter to preview data and create

dataset.

• Bind the dataset to controls.• In the Form Load event, use Adapter’s Fill method

to load the dataset:• OleDbDataAdapter1.Fill(DataSet11)

Creating Bound DataGridView

• DataGridView control:– Data Source property:

• DataSet

– Data Member property• A table in the dataset

– In the Form Load event, use Adapter’s Fill method to load the dataset:

• OleDbDataAdapter1.Fill(DataSet11)

Objects Related to Data Binding

• BindingContext: It is an object that manages a collection of data sources used for binding.

• CurrencyManager: It is an object that keeps track of position (the current row) of a data source. Two useful properties:– Position property: is the index of the current row. The

index is a 0-based index, the first record has a position of 0.

– Count property: The number of rows in the data source.

Binding Text Box

• Select Data Bindings property:– Text: choose field

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

source is stored in the CurrencyManager’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.• Note: Me.BindingContext(DataSet21, "customer") returns

a CurrencyManager object.

BindingSource Object

• BindingSource is an object that encapsulates a CurrencyManager and its properties and methods.

• It has two important properties: DataSource and DataMember.

• In case that the data source for a control changes, we only need to change the DataSource and DataMember properties.

BindingSource’s Position Property

• If controls are bound to a BindingSource object, to move the current record we change the Position property of the BindingSource object:– To move to the next record:

• Me.EmpBindingSource.Position += 1

– To move to the previous record:• Me.EmpBindingSource.Position -= 1

CurrencyManager

• Dim custCurrMgr As CurrencyManager

• Dim ordCurrMgr As CurrencyManager

• In a procedure:– ordCurrMgr = Me.BindingContext(Ds31, "orders")

– custCurrMgr = Me.BindingContext(Ds31, “customer")

– custCurrMgr.Position += 1

– ordCurrMgr.Position += 1

BindingNavigator Object

• This object automatically adds navigation buttons to the form.

• Property:– BindingSource property

Binding ListBox

• Example: Bind Customer Table’s CID field to a listbox.– Create a Adapter for Customer table , and generate the

dataset.– Add ListBox and set binding properties:

• Data Source: Customer table• Display Member: Field to display in the listbox.• Value Member: the actual values for items in the list box. To

display the selected item’s value in a text box, do:– Textbox1.text = ListBox1.SelectedValue

• Can we use TextBox1.text=ListBox1.SelectedItem?No!

Display Selected Record

• Bound textbox (same data source as the listbox):– If the Listbox and the textbox are bound to the

same BindingSource object, the textbox will automatically displays the record of the selected listbox item.

• Unbound textbox

ListBox SelectedItem Property

• How to display the selected record in unbound textbox?

• After binding to a data source, this property return a DataRowView object.

• What is DataRowView? – Object Browser:

• System.Data– DataRowView: Item property is the default property

• To retrieve a column from a DataRowView object (use 0-based index to identity a column):

• ListBox1.SelectedItem.Item(1) • Or: ListBox1.SelectedItem(1)• Or: ListBox1.SelectedItem(“Cname”)

An Easy Away to Create a Form with Listbox and Textboxes

• Example: Display CID in Listbox and Display other fields of a customer record in textboxes

• 1. Click the DataSource window• 2. Select the Customer table• 3. Select CID field and click the drop down list next to it to

change the CID field’s control to listbox.• 4. Drag the CID field to the form

– Change the DataSource property to CustomerBindingSource and Display member property to CID

• 5 Drag other fields to the form.

Using Object Browser

• View/Object Browser• DataSet object model:• System.Data

– DataSet• Relations• Tables

– Rows– Columns

• Use Object Browser to study object’s properties, methods.

Collection Structure

• Properties:– Count– Item(index), 0-based index

• Methods:– Clear, Add, Insert, Remove, etc.

DataSet Class Hierarchy• DataSet

– Tables: A collection of datatable objects– To retrieve a table from Tables:

• DataSet11.Tables.Item(“CUSTOMER”).• DataSet11.Tables(“CUSTOMER”).• DataSet11.CUSTOMER

– Rows: Each table has a Rows property which is a collection of dataRow objects

• To get the first row: DataSet11.Tables(“CUSTOMER”).Rows(0)

– Each DataRow object has a collection of fields. To retrieve a field:

• DataSet11.CUSTOMER.Rows(0).Item(1)

• How many tables in a dataset?

• How many records in a table?

Navigate and Display Records in Unbound Text Boxes

• Use code to assign field value to the text box’s text property.

• Example:– Dim drFound As DataRow– drFound = DataSet11.CUSTOMER.Rows(0)

• Or DataSet11.Tables(“CUSTOMER”).Rows(0)

– TextBox4.Text = drFound.Item("cname")• Or drFound.Item(1)

– Or: TextBox4.Text = DataSet11.CUSTOMER.Rows(0).Item(1)

– Or: DataSet21.Tables.Item("customer").Rows.Item(0).Item(1)

Implement MoveNext Button with Unbound Control

If rowIndex < DataSet11.CUSTOMER.Rows.Count-1 Then

rowIndex += 1

TextBox1.Text = DataSet11.Tables("customer").Rows(rowIndex).Item(0)

TextBox2.Text = DataSet11.CUSTOMER.Rows(rowIndex).Item(1)

Else

MsgBox("out of bound")

End If

Note: MovePrevious, MoveLast, MoveFirst?

Using Object Browser to Study OleDB Object

• System.Data– System.Data.OleDB

• OleDBConnection– Methods: New(), New(ConnectionString), Open(), Close()– Properties: ConnectionString, DataBase, Provider, TimeOut

• OleDBCommannd– Methods: ExecuteReader, ExecuteNonQuery– Properties: Connection, CommandType, CommandText,

Parameters

• OleDBDataAdapter– Methods: Fill– Properties: SelectCommand, InsertCommand, DeleteCommand,

UpdateCommand.

Use the Find method of Table’s Rows collection to find a record

• Gets the row that contains the specified primary key values.– DataSet41.CUSTOMER.Rows.Find(ListBox1.

SelectedValue)– The FIND method returns a DataRow object.

• Display the found record in unbound text boxes.

Code Example

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

Dim drFound As DataRow

drFound = DataSet41.CUSTOMER.Rows.Find(ListBox1.SelectedValue)

‘ Assume SelectedValue is CID

TextBox1.Text = drFound.Item("cname")

TextBox2.Text = drFound.Item("rating")

End Sub

Note: We can get the search value from other controls such as InputBox and Textbox.

How to Determine If Record Exists or Not

Dim foundRow As DataRowDim SearchValue as StringSearchValue=InputBox(“Enter CID”)foundRow = DataSet41.CUSTOMER.Rows.Find (SearchValue)If Not (foundRow Is Nothing) Then

TextBox1.Text = FoundRow.Item("cname")TextBox2.Text = FoundRow.Item("rating")

ElseMessagebox.show(“Record not exist”)

End If

Send Changes in a Bound DataGrid Back to the Database

• Updating records in DataGrid:– New records are added at the end of the grid.

– To delete a record, click the leftmost column to select the record, then press the delete key.

– Modify record

• Add an Update button that use adapter’s update method to send changes back to the data source:– OledbDataAdapter1.Update(Dataset11)

How to create a dataset with two tables and relation?

• Assuming we want to create a database with Customer and Orders tables:

• You need to create two adapters, one for the Customer table and one for the Orders table. Then generate dataset from the adapters.

• The dataset created from the two adapters will contain both tables.

• To create a relation between the two tables, double click the dataset to open the dataset’s design view. At the dataset’s design view, point to the Customer table and right click to Add relation.