Accessing Relational Data in ADONET

Accessing Relational Data Using Microsoft Visual Studio .NET

Overview

Overview of ADO.NET

Creating a Connection to a Database

Displaying a DataSet in a List-Bound Control

ADO.NET provides a set of classes for working with data. ADO.NET provides:

An evolutionary, more flexible successor to ADO

A system designed for disconnected environments

A programming model with advanced XML support

A set of classes, interfaces, structures, and enumerations that manage data access from within the .NET Framework

What is ADO.NET?

Using Namespaces

Use the Imports or using statement to import namespaces

Namespaces used with ADO.NET include:

System.Data

System.Data.SqlClient

System.Data.OleDb

Imports System.DataImports System.Data.SqlClientImports System.DataImports System.Data.SqlClient

using System.Data;using System.Data.SqlClient;using System.Data;using System.Data.SqlClient;

DataSet

SQL Server .NET Data Provider

OLE DB .NET Data Provider

SQL Server 7.0(and later)

OLEDB sources(SQL Server 6.5)

OleDbConnectionOleDbConnection

OleDbDataAdapterOleDbDataAdapterSqlDataAdapterSqlDataAdapter

SqlConnectionSqlConnection

DataTable

DataTable

The ADO.NET Object Model

SQL Server 2000

DataSet

DataTable

DataTable

Physical storage

OleDb Database

SqlDataAdapterSqlDataAdapter

SqlConnectionSqlConnection

DataTable

Client/Web server memory

OleDbDataAdapterOleDbDataAdapter

OleDbConnection

OleDbConnection

What is a Dataset?

Accessing Data with ADO.NET

DatabaseDatabase

4. Return the DataSet to the Client

5. Client manipulates the data

2. Create the SqlConnection and SqlDataAdapter objects

3. Fill the DataSet from the DataAdapter and close the connection

SqlDataAdapter

SqlConnection

List-Bound

Control

List-Bound

Control

1. Client makes request1111

2222

3333

4444

5555

6. Update the DataSet

7. Use the SqlDataAdapter to open the SqlConnection, update the database, and close the connection

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7777

ClientClient

Web serverWeb server

DataSet

Using Server Explorer to Generate a Connection

Create a new data connection by dragging a Table from Server Explorer

Create a new data connection using the Data Links dialog box

The DataAdapter Object Model

sp_SELECT

CommandCommand

SelectCommand UpdateCommand InsertCommand DeleteCommand

DataAdapter

CommandCommand CommandCommand CommandCommand

ConnectionConnection

sp_UPDATE sp_INSERT sp_DELETE

Database

DataSetDataSet

DataReaderDataReader

Store the query in a DataAdapter

The DataAdapter constructor sets the SelectCommand property

Set the InsertCommand, UpdateCommand, and DeleteCommand properties if needed

Creating a DataAdapter

Dim da As New SqlDataAdapter _("select * from Authors", conn)

Dim da As New SqlDataAdapter _("select * from Authors", conn)

da.SelectCommand.CommandText da.SelectCommand.Connection

da.SelectCommand.CommandText da.SelectCommand.Connection

SqlDataAdapter da = new SqlDataAdapter("select * from Authors",conn);

SqlDataAdapter da = new SqlDataAdapter("select * from Authors",conn);

da.SelectCommand.CommandText;da.SelectCommand.Connection;

da.SelectCommand.CommandText;da.SelectCommand.Connection;

Demonstration: Connecting to a Database

Expand Server Explorer to a table in a SQL Server database

Drag and Drop Data Access

Generating a DataSet

You can generate a DataSet…

…through the UI…Creates a DataSet that allows you to access data as an object

…or through code…

and then fill…

Dim ds As New DataSet()Dim ds As New DataSet()

DataAdapter1.Fill(ds)DataAdapter2.Fill(ds)DataAdapter1.Fill(ds)DataAdapter2.Fill(ds)

DataSet ds = new DataSet();DataSet ds = new DataSet();

DataAdapter1.Fill(ds);DataAdapter2.Fill(ds);DataAdapter1.Fill(ds);DataAdapter2.Fill(ds);

Storing Multiple Tables

Add the first table

Add the subsequent table(s)

daCustomers = New SqlDataAdapter _ ("select * from Customers", conn1)daCustomers.Fill(ds, "Customers")

daCustomers = New SqlDataAdapter _ ("select * from Customers", conn1)daCustomers.Fill(ds, "Customers")

Orders

Customers

daOrders = New SqlDataAdapter _ ("select * from Orders", conn2)daOrders.Fill(ds, "Orders")

daOrders = New SqlDataAdapter _ ("select * from Orders", conn2)daOrders.Fill(ds, "Orders")

conn2conn1

DataSet

Demonstration: Generating a DataSet

Create a typed DataSet from a DataAdapter

Add a second DataTable from a different DataAdapter

Show the schema of DataSet

What are List-Bound Controls?

Controls that connect to a data source and display the data

List-bound controls include the following:

DropDownList

ListBox

CheckBoxList

RadioButtonList

DataGrid

DataList

Repeater

Displaying DataSet Data in List-Bound Controls

Set the properties

Fill the DataSet, then call the DataBind methodDataAdapter1.Fill(ds)lstEmployees.DataBind()DataAdapter1.Fill(ds)lstEmployees.DataBind()

PropertyPropertyPropertyProperty DescriptionDescriptionDescriptionDescription

DataSourceDataSource The DataSet containing the data The DataSet containing the data

DataMemberDataMember The DataTable in the DataSet The DataTable in the DataSet

DataTextFieldDataTextField The field in the DataTable that is displayed The field in the DataTable that is displayed

DataValueFieldDataValueField The field in the DataTable that becomes the value of the selected item in the list

The field in the DataTable that becomes the value of the selected item in the list

DataAdapter1.Fill(ds);lstEmployees.DataBind();DataAdapter1.Fill(ds);lstEmployees.DataBind();

Demonstration: Binding List-Bound Controls to a Database

Add a DataGrid to a Windows Form

Set the DataSource and DataMember properties

Fill the DataSet

Web Forms DataGrid

An SQL example

<%@Page Language="c#"%>

<%@Import Namespace="System.Data" %>

<%@Import Namespace="System.Data.SqlClient" %>

<html>

<head>

<title> ASP.NET - Data - Data Table <br/>

Using Microsoft SQL Objects</title>

</head>

<body>

<h2>Display of Data in a Table (Grid) Using SQL Objects</h2>

Northwind Employees:<hr/>

<asp:datagrid id="dgrEmployees" runat="server" />

<script Language="c#" runat="server">

void Page_Load()

{

// First we will set up variables to hold two strings

string strSQL = "SELECT FirstName,LastName FROM Employees;";

string strConnection = "server=EWANB;";

strConnection += "database=Northwind;uid=sa;password=;";

DataSet objDataSet = new DataSet();

SqlConnection objConnection = new SqlConnection(strConnection);

// Create a new DataAdapter using the connection object and select statement

SqlDataAdapter objDataAdapter = new SqlDataAdapter(strSQL, objConnection);

// Fill the dataset with data from the DataAdapter object

objDataAdapter.Fill(objDataSet, "Employees");

// Create a DataView object for the Employees table in the DataSet

DataView objDataView = new DataView(objDataSet.Tables["Employees"]);

// Assign the DataView object to the DataGrid control

dgrEmployees.DataSource = objDataView;

dgrEmployees.DataBind(); // and bind [display] the data;

}

</script>

</body>

</html>

OleDB Example

<%@ Import Namespace="System.Data" %>

<%@ Import Namespace="System.Data.OleDb" %>


void Page_Load()

{

string strConnection = "Provider=Microsoft.Jet.OleDb.4.0;";

strConnection += @"Data Source=C:\BegASPNET\ch12\Northwind.mdb";

data_src.Text = strConnection;

string strSQL = "SELECT FirstName, LastName FROM Employees";


OleDbConnection objConnection = new OleDbConnection(strConnection);

OleDbDataAdapter objAdapter = new OleDbDataAdapter(strSQL, objConnection);

objAdapter.Fill(objDataSet, "Employees");

DataView objDataView = new DataView(objDataSet.Tables["Employees"]);

dgNameList.DataSource=objDataView;

dgNameList.DataBind();

}

</script>

<html>

<body>

<h4>Reading data from the connection

<asp:label id="data_src" runat="server"/> to the DataGrid control.</h4>

<asp:datagrid id="dgNameList" runat="server" /><br />

</body>

</html>

Editing Data




void Page_Load(object sender, EventArgs e)

{

string strConnection, strSQL;


OleDbConnection objConnection = null;

OleDbDataAdapter objAdapter = null;

OleDbCommandBuilder objBuilder = null;

// Set the connection and query details

strConnection = "Provider=Microsoft.Jet.OleDb.4.0;";


strSQL = "SELECT FirstName, LastName FROM Employees;";

objConnection = new OleDbConnection(strConnection);

objAdapter = new OleDbDataAdapter(strSQL, objConnection);

objAdapter.Fill(objDataSet, "Employees");

dgNameList1.DataSource = objDataSet.Tables["Employees"].DefaultView;

dgNameList1.DataBind();

// -----------------------------------------------------------------

// Marker 1

DataTable objTable = objDataSet.Tables["Employees"];

DataRow objNewRow = objTable.NewRow();

objNewRow["FirstName"] = "Norman";

objNewRow["LastName"] = "Blake";

objTable.Rows.Add(objNewRow);

// Bind the data grid to the new data

dgNameList2.DataSource = objTable.DefaultView;


// -----------------------------------------------------------------

// Marker 2

// Find the row to change

DataRow[] objRows = objTable.Select("FirstName='Margaret' AND LastName='Peacock'");

objRows[0]["FirstName"] = "John";

objRows[0]["LastName"] = "Hartford";




// -----------------------------------------------------------------

// Marker 3

// The Rows collection is 0 indexed, so this removes the sixth row

objTable.Rows[5].Delete();




}

</script>

<html>

<body>

<table width="100%">

<tr>

<td>Original Data</td>

<td>Data with new Row</td>

<td>Data with edited Row</td>

<td>Data with deleted Row</td>

</tr>

<tr>

<td valign="top"><asp:DataGrid id="dgNameList1" runat="server" /></td>




</tr>

</table>

</body>

</html>

Command Object




void Page_Load(object sender, EventArgs e)

{

string strConnection, strSQL;


OleDbConnection objConnection = null;

OleDbDataAdapter objAdapter = null;

OleDbCommand objCommand = null;

OleDbCommandBuilder objBuilder = null;

// Set the connection and query details

strConnection = "Provider=Microsoft.Jet.OleDb.4.0;";


strSQL = "SELECT EmployeeID, FirstName, LastName FROM Employees";

// Open the connection and set the command

objConnection = new OleDbConnection(strConnection);

objAdapter = new OleDbDataAdapter(strSQL, objConnection);

// Create the other commands

objBuilder = new OleDbCommandBuilder(objAdapter);

objAdapter.UpdateCommand = objBuilder.GetUpdateCommand();

objAdapter.InsertCommand = objBuilder.GetInsertCommand();

objAdapter.DeleteCommand = objBuilder.GetDeleteCommand();

// Now display the CommandText property from each command

lblSelectCommand.Text = objAdapter.SelectCommand.CommandText;

lblUpdateCommand.Text = objAdapter.UpdateCommand.CommandText;

lblInsertCommand.Text = objAdapter.InsertCommand.CommandText;

lblDeleteCommand.Text = objAdapter.DeleteCommand.CommandText;

}

</script>

<html>

<body>

<table border="1">

<tr>

<td>Command</td>

<td>CommandText</td>

</tr>

<tr>

<td>SelectCommand</td>

<td><asp:Label id="lblSelectCommand" runat="server" />

</tr>

<tr>

<td>UpdateCommand</td>

<td><asp:Label id="lblUpdateCommand" runat="server" />

</tr>

<tr>

<td>InsertCommand </td>

<td><asp:Label id="lblInsertCommand" runat="server" />

</tr>

<tr>

<td>DeleteCommand</td>

<td><asp:Label id="lblDeleteCommand" runat="server" />

</tr>

</table>

</body>

</html>

Technology

Accessing Relational Data in ADONET