Module 16 (Optional):

Contents Overview 1 Connecting to a Data Source 10 Accessing Data with DataSets 12 Lab 16: Using ADO.NET to Access Data 34 Accessing Data with DataReaders 42 Review 56 Module 16 Op

Contents

Overview 1

Connecting to a Data Source 10

Accessing Data with DataSets 12

Lab 16: Using ADO.NET to Access Data 34

Accessing Data with DataReaders 42

Review 56

Module 16 (Optional): Using Microsoft

ADO.NET to Access Data

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Instructor Notes

This module focuses on using ADO.NET to access data from various data sources

After completing this module, students will be able to:

! Describe the ADO.NET object model

! Connect to a data source by using ADO.NET

! Retrieve data from a database by using DataReaders and DataSets

! Display the data from a database on the client by using DataGrid controls

! Use stored procedures to read data from a data source

! Read data from an XML file into DataSets

Materials and Preparation

This section provides the materials and preparation tasks that you need to teach this module

Required Materials

To teach this module, you need the Microsoft® PowerPoint® file 2349B_16.ppt

Preparation Tasks

To prepare for this module, you should:

! Read all of the materials for this module

! Complete all of the demonstrations

! Complete the lab

! Go through the animation

Presentation:

120 Minutes

Lab:

60 Minutes

Multimedia Presentation

This section provides multimedia presentation procedures that do not fit in the margin notes or are not appropriate for the student notes

Using ADO.NET to Access Data

! To present the animation

Start animation There are two ways to access data from a database by using

ADO.NET: by using a DataSet or by using a DataReader

This animation demonstrates how these two methods work and highlights their differences

Click Start Click DataSet The DataSet method is a disconnected way to access data

from a database

In this method, when a user requests data from a database, the

DataAdapter object is used to create a DataSet, which is

basically a collection of data tables from the database that also retains the relationships between these tables Notice

that, after a DataSet is populated, it is disconnected from the

database

To display the data from the DataSet, you set up a DataView for the desired table The DataView is then bound to a list-

bound control for displaying purposes You can use any of

the three list-bound controls, DataGrid, Repeater, or

DataList, to display data

The data in the list-bound control is then displayed on the client

An important point to make here is that the use of a

DataView to display data is necessary only in ASP.NET

Beta 1 From the Beta 2 version onward, you can directly

bind the DataSet to a list-bound control

Click DataReader This method is similar to the Microsoft ActiveX® Data

Objects (ADO) way of accessing data by using recordsets

In this method, when a user requests data from a database, the

Command object retrieves the data into a DataReader A DataReader is a read-only/forward-only view of the data A DataReader works similarly to a Recordset in ADO,

allowing you to simply loop through the records Like the

ADO Recordset, the DataReader is connected to the

database You must explicitly close the connection when you are finished reading data

Module Strategy

Use the following strategy to present this module:

! Overview of ADO.NET This section provides students with an overview of ADO.NET The section begins a description of the objects used when connecting to a database both

with a DataReader and a DataSet Point out to students that there are

Microsoft SQL Server™ and ADO versions of many of these objects After

describing the process of accessing data through a DataReader and a DataSet, show the animation Because students may be familiar with ADO,

this may be an ideal time to discuss some of the main differences between ADO and ADO.NET

When talking about using namespaces, explain their significance to the students

! Connecting to a Data Source From this point onward, students will actually start working with ADO.NET Tell them that all of the examples in this module use

SqlConnection objects rather than OleDbConnection objects Direct the

students to the Microsoft NET Framework software development kit (SDK) documentation for more information

! Accessing Data with DataSets

ADO.NET provides two ways to access data, the DataSet and the DataReader This section focuses on accessing data by using the DataSet The DataSet represents a new concept, so spend additional time on this

section The demonstrations actually show every aspect of data access with ADO.NET Go through the demonstrations carefully, and make sure that the students understand the details

! Using Stored Procedures Most students who have worked with a SQL Server database and ADO will have experience with using stored procedures This section provides the students with information about how to use stored procedures and parameterized stored procedures with ADO.NET

! Lab16: Using ADO.NET to Access Data The lab for this module is encountered in the middle of the module This is because the module is long and also because the lab does not use material from the last two sections in the module

! Accessing Data with DataReaders

This section focuses on accessing data by using a DataReader Point out to the students that, when they use a DataReader, the database connection is

always open When they are finished reading data, they must explicitly close the connection

! Binding to XML Data XML is fast emerging as the most popular language for exchanging data This section provides students with information on how to read XML data

by using ADO.NET

Most students will already know about XML documents However, for students who are not familiar with XML, it will be useful to show an example of an XML document and how it is displayed on the client

Overview

! Overview of ADO.NET

! Connecting to a Data Source

! Accessing Data with DataSets

! Using Stored Procedures

! Accessing Data with DataReaders

! Binding to XML Data

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ADO.NET, offers a rich suite of data handling and data binding functions for manipulating all types of data ADO.NET is an evolution of the ADO data access model that directly addresses user requirements for developing scalable applications It was designed specifically for the Web with scalability,

statelessness, and XML in mind

After completing this module, you will be able to:

! Describe the ADO.NET object model

! Connect to a data source by using ADO.NET

! Retrieve data from a database by using DataReaders and DataSets

! Display the data from a database on the client by DataGrid controls

! Use stored procedures

! Read data from an XML file into DataSets

In this module, you will learn

about the data binding

features in ASP.NET

" Overview of ADO.NET

! The ADO.NET Object Model

! RecordSets vs DataSets

! Using Namespaces

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ADO.NET is not a revision of Microsoft® ActiveX® Data Objects (ADO), but a new way to manipulate data that is based on disconnected data and XML Although ADO is an important data access tool it is connected by default, relies

on an OLE DB provider to access data, and it is entirely Component Object Model (COM)-based

ADO.NET has been designed to work with disconnected datasets Disconnected datasets reduce network traffic

ADO.NET uses XML as the universal transmission format This guarantees interoperability as long as the receiving component runs on a platform where an XML parser is available When the transmission occurs through XML, it is no longer necessary that the receiver be a COM object The receiving component has no architectural restrictions whatsoever Any software component can share ADO.NET data, as long as it uses the same XML schema for the format of the transmitted data

In this section, you will learn about ADO.NET You will learn about the new and modified objects in ADO.NET You will also learn about some of the new namespaces

Topic Objective

To introduce the topics

included in this section

Lead-in

ASP.NET offers a new

means to retrieve data with

the introduction of

ADO.NET

The ADO.NET Object Model

DataAdapter

Connection Database

Command

.ASPX Page

List-Bound Control

List-Bound Control

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ADO.NET evolved from the ADO data access model By using ADO.NET, you can develop applications that are robust and scalable, and that can use XML

ADO.NET has some of the same objects as ADO (like the Connection and Command objects), and introduces new objects, such as the Dataset, DataReader, and DataAdapter

Connection Objects

Connection objects are used to talk to databases They have properties, such as DataSource, UserID, and Password, which are needed to access a particular DataSource Commands travel over connections, and result sets are returned in the form of streams that can be read by DataReaders or pushed into DataSet

objects

There are two kinds of connection objects in ADO.NET: SqlConnection and OleDbConnection

Command Objects

Command objects contain the information that is submitted to a database A

command can be a stored procedure call, an update statement, or a statement that returns results You can also use input and output parameters and return values In ADO.NET, you can use two kinds of command objects:

SqlCommand and OleDbCommand

Topic Objective

To describe the ADO.NET

object model

Lead-in

ADO.NET includes some of

the same objects as ADO

(like Connection and

Command), and introduces

new objects, such as

DataSets , DataReaders

and DataAdapters

Delivery Tip

Point out that there are ADO

and SQL Server versions of

the Connection,

Command , DataAdapter,

and DataReader objects

DataReader Objects

A DataReader is somewhat synonymous with a read-only/forward-only view

of the data The DataReader API supports flat as well as hierarchical data A DataReader object is returned after executing a command against a database It

works similarly to a recordset in ADO; however the format of the returned

DataReader object is different from a recordset For example, you may use the DataReader to show the results of a search list in a Web page.

ADO.NET includes two types of DataReader objects: the SqlDataReader for

Microsoft SQL Server™ version 7.0 (or later) data, and the OleDbDataReader for ADO data The DataReader object is database-specific The behavior of the SqlDataReader may differ from the behavior of the OleDbDataReader and additional DataReader objects that are introduced in the future

You use the OleDbCommand and SqlCommand objects and the ExecuteReader method to transfer data into a DataReader

DataSet Objects

The DataSet object is similar to the ADO Recordset object, but more powerful, and with one other important distinction: the DataSet is always

disconnected. The DataSet provides a rich object model to work with when

passing data between various components of an enterprise solution The

DataSet object represents a cache of data, with database-like behavior It

contains tables, columns, relationships, constraints, and data Data coming from

a database, an XML file, code, or user input can be entered into DataSet objects and converted into files, forms, or databases The behavior of a DataSet is

completely consistent regardless of the underlying database, SQL Server or

OLE DB As changes are made to the DataSet, they are tracked in a way

similar to the way changes are tracked in a word processing document

The DataSet object has a collection of DataTable objects A DataTable

represents one table of in-memory data It contains a collection of columns that

represents the table's schema A DataTable also contains a collection of rows,

representing the data contained in the table

You use the OleDbDataAdapter and SqlDataAdapter objects and the Fill method to get data into a DataSet

DataView Objects

A DataView enables you to create different views of the data stored in a DataTable, a capability that is often used in data-binding applications By using a DataView, you can expose the data in a table with different sort orders,

and you can filter the data by row state or based on a filter expression

A DataView provides a dynamic view of data whose content, ordering, and membership reflect changes to the underlying DataTable as they occur This is different from the Select method of the DataTable, which returns a DataRow

array from a table per a particular filter and/or sort order, and whose content reflects changes to the underlying table, but whose membership and ordering

remain static The dynamic capabilities of the DataView make it ideal for

data-binding applications

DataAdapter Object

While the DataSet object provides a tool for in-memory data storage, you need

another tool to create and initialize the various tables This tool is the

DataAdapter object It represents a centralized console that hides the details of working with connections and commands The DataAdapter object allows for the retrieval and saving of data between a DataSet object and the source data

store It is responsible for pulling out data from the physical store and pushing it

into data tables and relations The DataAdapter object is also responsible for

transmitting any update, insertion, or deletion to the physical database You can

use four command objects to make any updates: UpdateCommand, InsertCommand, DeleteCommand, and SelectCommand

The DataAdapter object exists in two forms: SqlDataAdapter objects and OleDbDataAdapter objects The data source is SQL Server for

SqlDataAdapter objects and any other OLE DB provider for OleDbDataAdapter objects

The following illustration shows the use of a SQLDataAdapter object to transfer data between a SQL Server database and a DataSet object

Multimedia: Using ADO.NET to Access Data

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In this animation, you will learn how to access data by using ADO.NET and how you can display that data in an ASP.NET page To view the animation,

open the file 2349B_16A001.htm file from the Media folder

Topic Objective

To provide a high-level

overview of how to access

data by using ADO.NET

Lead-in

In this animation, you will

learn about how ADO.NET

accesses data and how you

can display that data in an

ASP.NET page

Delivery Tip

Tell students that they can

view the animation again

later for themselves by

opening the

2349B_mod3.htm file from

the Media folder

For details about how to run

and describe the animation,

see the Multimedia

Presentation section in the

Instructor Notes for this

module

Recordsets vs DataSets

Transmit XML fileCOM marshalling

Transmitting data

DisconnectedConnected or

disconnectedData connections

Navigate via relationshipsMove row-by-row

Moving through data

Includes relationshipsBased on join

Relationships

Multiple tablesOne table

Number of tables

DataSet Recordset

Feature

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In ADO, the in-memory representation of database data is the recordset In

ADO.NET, it is the DataSet The DataSet contains a collection of tables and

knowledge of relationships between those tables Each table contains a

collection of columns These objects represent the schema of the DataSet Each table can then have multiple rows, representing the data held by the DataSet

These rows track their original state along with their current state, so that the

DataSet tracks what kinds of changes have occurred Additionally, the DataSet

provides persistence and de-persistence through XML

There are important differences between recordsets and DataSets, which are highlighted in the following table and detailed in the text that follows

Number of Tables

An ADO recordset looks like a single table If a recordset is to contain data

from multiple database tables, it must use a JOIN query, which assembles the

data from the various database tables into a single result table

In contrast, an ADO.NET DataSet is a collection of one or more tables The tables within a data set are called data tables; specifically, they are DataTable

objects

Topic Objective

To highlight the differences

between DataSets and

Recordsets

Lead-in

In ADO, you used

Recordsets

Relationships

Typically, a DataSet also contains relationships A relationship within a DataSet is analogous to a foreign-key relationship in a database In ADO.NET,

a DataRelation represents the relationship

Moving Through Data

In ADO.NET, the methods you use to read or modify data differ from the programming methods you use in ADO in the following ways:

! In ADO, you scan sequentially through the rows of the recordset

! In ADO.NET, rows are represented as collections, so you can loop through

a table as you would through any collection or access particular rows

through ordinal or primary key index DataRelation objects maintain

information about master and detail records and provide a method that allows you to get records related to the one you are working with For example, starting from the row of the Investor table for "Jose Lugo", you can navigate to the set of rows of the Purchase table that describes the purchases made by Jose Lugo

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The Microsoft NET Framework is an object-oriented system When using specific parts of the framework, you must include references to the appropriate namespace

When using ADO.NET from either Microsoft Visual Basic® or Microsoft VisualC#™, you must reference the System.Data namespace, plus either the System.Data.OleDb or System.Data.SqlClient namespace, depending on the data source you choose to use System.Data provides the code facilities, while System.Data.OleDb and System.Data.SqlClient are the namespaces for the two managed providers The System.Data.Common namespace contains classes that are shared by the NET data providers The System.Data.SqlTypes

namespace provides classes for native data types within SQL Server These classes provide a safer, faster alternative to other data types

The following table summarizes the list of available namespaces with ADO.NET

Namespace Contains System.Data Base objects and types for ADO.NET

System.Data.OleDb Managed OLE DB data store objects

System.Data.SqlClient SQL Server specific implementations of ADO.NET objects

System.Data.Common Classes shared by the NET data providers

System.Data.SqlTypes SQL data types

Topic Objective

To describe the new

namespaces used with

ADO.NET

Lead-in

In.NET, you must specify

the namespace that you

want to use

Connecting to a Data Source

OleDbConnection myOleDbConnection = newOleDbConnection("server=(local)\\NetSDK; !Trusted_Connection=yes;database=northwind; !provider=sqloledb");

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When you connect to a database, there are two routes that you can take: use OLE DB or use the native SQL provider The native SQL provider is faster, but you must use Microsoft SQL Server as your database If you are using

Microsoft Access, Microsoft Excel, a comma-delimited file, or some other data source, you must use the OLE DB provider You can use the OLE DB provider with a Microsoft SQL Server database; however, it is not as fast as using the native SQL provider

The Connection object defines how to connect to a specific data store The NET Framework provides two Connection objects: SqlConnection and OleDbConnection The SqlConnection object defines how to connect to SQL Server databases and the OleDbConnection object allows you to establish

a connection to a database through an OLE DB provider

Using SqlConnection

The following code illustrates how to create and open a connection to a

Microsoft SQL Server database by using the SqlConnection object

SqlConnection mySqlConnection = new SqlConnection("server=(local)\\NetSDK;!

Trusted_Connection=yes;database=northwind");

Embedded usernames/passwords in database connection strings are inherently unsecure, and should only be used on platforms, such as Microsoft Windows® 9x, that do not support Integrated Security

For more information about Integrated Security, see the NET Framework SDK documentation

Topic Objective

To describe how to connect

to a data source by using

ADO.NET

Lead-in

Connecting to a data source

is the first step in data

access

Delivery Tip

Point out to students that in

ADO.NET you do not

always need to explicitly

open and close the

connection to the database

Warning

Using OleDbConnection

For the OLE DB Managed Provider, the connection string format is quite similar to the connection string format used in OLE DB

The following code illustrates how to create and open a connection to a

Microsoft SQL Server database by using OleDbConnection

OleDbConnection myOleDbConnection = new OleDbConnection("server=(local)\\NetSDK;!

Trusted_Connection=yes;database=northwind;!

provider=sqloledb");

The examples in this module, use SqlConnection objects Implementation is slightly different for using OleDbConnection objects For more information about using OleDbConnection objects, search for OleDbConnection in the

Microsoft NET Framework SDK documentation

Choosing a NET Data Provider

Depending on the design and data source for your application, your choice of NET data provider can improve the performance, capability, and integrity of your application The following table discusses the advantages and limitations

of each NET data provider

Provider Notes

SQL Server NET Data Provider

Recommended for middle-tier applications that use Microsoft SQL Server 7.0 or later

Recommended for single-tier applications that use Microsoft Data Engine (MSDE) or Microsoft SQL Server 7.0 or later Recommended over use of the OLE DB Provider for SQL Server (SQLOLEDB) with the OLE DB NET Data Provider

For Microsoft SQL Server version 6.5 and earlier, you must use the OLE DB Provider for SQL Server with the OLE DB NET Data Provider

OLE DB NET Data Provider

Recommended for middle-tier applications that use Microsoft SQL Server 6.5 or earlier, or any OLE DB provider that supports the OLE DB interfaces listed in OLE DB Interfaces Used by the OLE DB NET Data Provider (OLE DB 2.5 interfaces are not required)

For Microsoft SQL Server 7.0 or later, the SQL Server NET Data Provider is recommended

Recommended for single-tier applications that use Microsoft Access databases Use of a Microsoft Access database for a middle-tier application is not recommended

Support for the OLE DB Provider for ODBC (MSDASQL) is disabled For access to Open Database Connectivity (ODBC) data sources, an ODBC NET Data Provider is available as a separate download at http://msdn.microsoft.com/downloads

Delivery Tip

Stress to students that all

examples in the module and

lab will use SqlConnection

objects

" Accessing Data with DataSets

! Using DataSets to Read Data

! Storing Multiple Tables in a DataSet

! Using DataViews

! Updating a Database from a DataSet

! Displaying Data in the DataGrid Control

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ADO.NET provides two ways to access data, DataSets and DataReaders

In this section, you will learn how to access data by using DataSets You will also learn about DataViews and displaying data in DataGrid controls

Topic Objective

To introduce the topics

included in the section

Lead-in

After connecting to a

database, the next step is to

access data from it

Using DataSets to Read Data

! Create the Database Connection

! Store the Query in a SqlDataAdapter

! Create and Populate the DataSet with DataTables

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(

"select * from customers", mySqlConnection);

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(

"select * from customers", mySqlConnection);

DataSet myDataSet = new DataSet();

mySqlDataAdapter.Fill(myDataSet,"Customers");

DataSet myDataSet = new DataSet();

mySqlDataAdapter.Fill(myDataSet,"Customers");

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After you establish a connection to a database, you can access its data

ADO.NET provides multiple ways to access data

Using DataSets

The DataSet object is the centerpiece of ADO.NET It represents a complete

set of data, including multiple, related tables, and constraints

Although a DataSet stores data, you need DataAdapter objects to create and initialize the various tables You also need the Fill method to populate a DataSet with the results from a query

The Fill method takes two parameters: a DataSet instance and a string The DataSet instance represents the DataSet to be filled, and the string identifies the DataTable that will be created inside the DataSet A DataSet can contain many DataTables You use the string supplied to the Fill method to reference the DataTable after it is created

Topic Objective

To describe how to retrieve

data from a database by

using DataSets

Lead-in

Now that we can establish a

connection, we need to be

able to execute statements

against the database to

retrieve data

Delivery Tip

Explain the parameters to

the Fill method The second

parameter is the name that

will be given to the

DataTable created in the

DataSet You use this name

when reading data from the

DataSet

The following code example illustrates how to create a SqlDataAdapter object that contains the query statement The Fill method then populates the DataSet

with the results from the query

// Create a connection SqlConnection mySqlConnection = new SqlConnection("server=(local)\\NetSDK;!

Trusted_Connection=yes;database=northwind");

// Create the DataAdapter SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(

"select * from customers", mySqlConnection);

// Create and populate the DataSet DataSet myDataSet = new DataSet();

mySqlDataAdapter.Fill(myDataSet,"Customers");

Displaying Data In A DataSet

Because the data is stored in a collection of rows in the table, you can easily use

a foreach statement to iterate through the rows:

foreach (DataRow myDataRow in myDataSet.Tables["Customers"].Rows) {

Console.WriteLine(

" CustomerID: {0}", myDataRow["CustomerID"].ToString);

}

Typed DataSet

Along with late bound access to values through weakly typed variables, the

DataSet provides access to data through a strongly typed metaphor By using

user-friendly names and strongly typed variables, you can access tables and

columns that are part of the DataSet You can also transport a strongly typed DataSet by using an XML Web service

A typed DataSet is a class that derives from a DataSet As such, it inherits all

of the methods, events, and properties of a DataSet Additionally, a typed DataSet provides strongly typed methods, events, and properties This means

that you can access tables and columns by name, instead of using based methods Aside from the improved readability of the code, a typed

collection-DataSet also allows the Microsoft Visual Studio® NET code editor to automatically complete lines as you type

Additionally, a strongly typed DataSet provides access to the correct types for values at compile time With a strongly typed DataSet, type mismatch errors

are caught when the code is compiled rather than at run time

Using an XML Schema that complies with the XML Schema definition

language (XSD) standard, you can generate a strongly typed DataSet by using

the XSD.exe tool that is provided with the NET Framework SDK The use of this tool is outside the scope of this module

You will see how to easily create and use a typed DataSet using Visual Studio

.NET in this module’s lab

Storing Multiple Tables in a DataSet

! Add the First Table

! Add the Subsequent Table(s)

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(

"select * from customers",mySqlConnection);

DataSet myDataSet = new DataSet();

mySqlDataAdapter.Fill(myDataSet,"Customers");

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(

"select * from customers",mySqlConnection);

DataSet myDataSet = new DataSet();

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A DataSet can contain multiple tables You can retrieve multiple tables from a database and store them in a DataSet

You can store tables from different databases in the same DataSet

! To retrieve and store multiple tables in a DataSet

1 Create and populate the first DataSet

DataSet myDataSet = new DataSet();

string strSql ="select * from customers";

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(

To explain how to retrieve

and store multiple tables in

a DataSet

Lead-in

Unlike a disconnected

recordset, a DataSet can

hold more than one table

Note

Delivery Tip

Tell students that they can

create new relationships

between the tables in a

DataSet

The following code shows how you can add two tables from two different

queries, one for authors and the other for titles, to the same DataSet

// create connection to database string strConn =

//fill DataSet with first set of data DataSet myDataSet = new DataSet();

DataView myDataView =myDataSet.Tables["Customers"].DefaultView;

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There are many ways to filter data One way is to filter data at the database

command level, by using a where clause in your query A second way is to filter the data after it is in the DataSet This topic covers filtering in the DataSet

Filtering and Sorting with DataViews

To display the data held in a DataSet, you can use a DataView

DataViews can be customized to present a subset of data from the DataTable This capability allows you to have two controls bound to the same DataTable,

but showing different versions of the data For example, one control may be

bound to a DataView that shows all the rows in the table, and a second may be configured to display only the rows that have been deleted from the DataTable Each DataTable in a DataSet has a DefaultView property, which returns the default view for the table You can access the default DataView of a DataSet

as follows:

DataView myDataView = myDataSet.Tables["Customers"].DefaultView;

The DataSet object contains a Tables collection You reference the DataTable you are interested in by name

You can sort the data For example, you can sort the customers by country myDataView.Sort = "Country";

Setting up a Different View of a DataSet

You can also create a view of a subset of the data in a DataTable For example, you can set the RowFilter property on a DataView to retrieve only customers

from Argentina

myDataView.RowFilter = "Country = 'Argentina'";

For more information about the properties of the DataView object, see the

Microsoft NET Framework SDK documentation

Updating a Database From a DataSet

! SQLCommandBuilder generates Update command

! Set the MissingSchemaAction property

myDataRow["CustomerId"] = "NewID";

//

myDataSet.Tables["Customers"].Rows.Add(myDataRow);

DataRow myDataRow =myDataSet.Tables["Customers"].NewRow();

myDataRow["CustomerId"] = "NewID";

//

myDataSet.Tables["Customers"].Rows.Add(myDataRow);

mySqlDataAdapter.Update(myDataSet, "Customers");

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This topic illustrates how to update data in a database by using a DataSet You

can also insert, update, and delete data in a database directly by using a

SqlCommand as described in the NET Framework SDK documentation After a DataSet is loaded, you can modify the data, and the DataSet will track the changes The DataSet may be considered an in-memory cache of data that

is retrieved from a database In this topic, you will see how to use the Add method on the DataTable to add new data to a DataSet The Add method takes either an array of the expected data columns, or a DataRow

To load the DataSet from the database:

SqlConnection myConnection = new SqlConnection(

"server=(local)\\NetSDK;!

Trusted_Connection=yes;database=northwind");

SqlDataAdapter mySqlDataAdapter = new SqlDataAdapter(

"Select * from Customers", myConnection);

DataSet myDataSet = new DataSet();

Before you can submit the update back to the database, you must set up the

InsertCommand, UpdateCommand, and DeleteCommand to reconcile the

changes to the database For limited scenarios you can use the

SqlCommandBuilder to automatically generate those for you:

SqlCommandBuilder mySqlCommandBuilder = new SqlCommandBuilder(mySqlDataAdapter);

This topic illustrates how to

update data in a database

using a DataSet You can

also insert, update, and

delete data in a database

directly using a

SqlCommand as described

in the NET Framework

SDK

Because Fill will not cause primary key and unique key information to be retrieved unless AddWithKey is specified, you must set the

MissingSchemaAction property to AddWithKey:

mySqlDataAdapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;

myDataRow["CustomerId"] = "NewID";

myDataRow["ContactName"] = "New Name";

myDataRow["CompanyName"] = "New Company Name";

You can also access a specific row by the primary key value:

DataRow myDataRow1 = myDataSet.Tables["Customers"].Rows.Find("ALFKI"); myDataRow1["ContactName"]="Peach";

In the preceding example, "ALFKI" is the value of the primary key

"CustomerID" in the Customers table When using the SqlDataAdapter, the

key is established from the database You can also set the key through the

PrimaryKey property if you are not using the database

Use the Delete method to remove the Row Note that a logical deletion occurs

in the DataSet, which only results in a hard deletion after the DataSet is updated to the database Similarly, you can use RejectChanges on the DataSet,

in which case the Row is restored

myDataSet.Tables["Customers"].Rows[0].Delete();

The original and new values are maintained in the row The RowChanging

event allows you to access both original and new values to decide whether you want the edit to proceed Because original and new values are maintained, you can establish scenarios such as optimistic locking and key changes

Demonstration: Accessing Data with DataSets

***************************** ILLEGAL FOR NON - TRAINER USE ******************************

In this demonstration, you will see how to access data with a DataSet

Run the Visual Studio NET Accessing Data with DataSets project from the

open a database, create a

DataSet with multiple tables,

and create views on the

data

Lead-in

In this demonstration, you

will see how to access data

with a DataSet

Tip

Running this program produces output that is similar to the following: Opened Connection to!

server=(local)\NetSDK;!

Trusted_Connection=yes;database=northwind Total Number of Regions: 4

Total Number of Customers: 91 Regions:

ID: 1 Description: Eastern ID: 2 Description: Western ID: 3 Description: Northern ID: 4 Description: Southern First 5 Customer IDs:

Customer ID: ALFKI Customer ID: ANATR Customer ID: ANTON Customer ID: AROUT Customer ID: BERGS View sorted by country First 5 Customers in the view:

Customer ID: CACTU Country: Argentina Customer ID: OCEAN Country: Argentina Customer ID: RANCH Country: Argentina Customer ID: ERNSH Country: Austria Customer ID: PICCO Country: Austria Filtered by country equals Argentina Customers with Country = Argentina, number of entries 3 ID: CACTU Country: Argentina

ID: OCEAN Country: Argentina ID: RANCH Country: Argentina

Displaying Data in the DataGrid Control

! Create a Windows Forms DataGrid control

! Bind to a DataSet

! Using a custom view

dataGrid1 = new System.Windows.Forms.DataGrid();

***************************** ILLEGAL FOR NON - TRAINER USE ******************************

Displaying data from a data source is extremely simple and flexible in either Windows Forms or ASP.NET These application development environments include a set of controls that perform the function of displaying data You only need to bind these controls to a data source

To display data on the client, you can use any list-bound control, such as the

DataGrid

Using the DataGrid Control

The DataGrid control is designed to produce output that resembles a worksheet In Visual Studio NET, you can drag and drop a DataGrid from the Toolbox onto the Design window This generates code to create a DataGrid

object as follows:

dataGrid1 = new System.Windows.Forms.DataGrid();

To bind a DataSet to a DataGrid control, you first set the DataSource property of the DataGrid to a DataTable, or DataVieweither the

DefaultView property of a DataSet or a custom DataView object

To specify a DataTable, set the DataMember property of the DataGrid to the name of the DataTable

Topic Objective

To describe how to display

data on the client DataGrid

controls

Lead-in

After you connect to a data

source and retrieve data

from it, the next step is to

display the data on the

client

Example Binding to a DataSet

example, the following code will display only those customers in Argentina

Example Using a Custom View

DataView myDataView = myDataSet.Tables["Customers"].DefaultView;

myDataView.RowFilter = "Country = 'Argentina'";

dataGrid2.DataSource = myDataView;

Demonstration: Displaying Data in a DataGrid

***************************** ILLEGAL FOR NON - TRAINER USE ******************************

In this demonstration, you will see how to read data from a database into a

DataSet and then display it in a DataGrid control

Run the Visual Studio NET DataGrid project from the following location:

<install folder>\Democode\Mod16\Demo16.2

Running this program displays a button labeled “Load Data” and two DataGrid

controls Clicking the button reads region and customer data from a database

and displays them in the grids A DataView object is used to display only those

customers in Argentina

Topic Objective

To introduce the Data Grid

Lead-in

In this demonstration, you

will see how to create a

Windows Form that reads

data from a database and

displays it in a DataGrid

control

" Using Stored Procedures

! Calling Stored Procedures

! Passing Parameters

! Calling Action Stored Procedures

***************************** ILLEGAL FOR NON - TRAINER USE ******************************

In the past, data processing has been primarily connection-based Now, in an effort to make multi-tiered applications more efficient, data processing is turning to a message-based approach that revolves around chunks of

information In ADO.NET, this is accomplished by the DataAdapter object, which provides a bridge to retrieve and save data between a DataSet object and its source data store The DataAdapter object accomplishes this by invoking

the appropriate SQL commands against the data store

Both the SqlDataAdapter and the OleDbDataAdapter classes feature four command objects, InsertCommand, UpdateCommand, DeleteCommand, and SelectCommand These objects provide the create, update, delete, and read functions for a specific DataTable in the DataSet

These command objects are used when you want to perform a number of updates at the same time Instead of having one stored procedure to do it all,

you can put SQL Statements in each object and call the Update method

For more information about these command objects, see the NET Framework SDK documentation

However, the easier and more commonly used method of updating data in a database is to use stored procedures You can use stored procedures to read and modify data from a database You can call stored procedures both from

DataAdapter and Command objects

In this section, you will learn how to call stored procedures, pass parameterized stored procedures, and call action stored procedures

Topic Objective

To introduce the topics in

this section

Lead-in

When working with data

from a data source, the

ability to use stored

procedures is important