17. Data Access
ADO.Net Architecture
New
Features of ADO.NET
Visual Studio Visual Studio Wizards and
Designers
Demonstration: Creating Data Components
Lab 17: Accessing Data Using ADO.NET
Code Samples
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ADO.NET Architecture
 What
Is ADO.NET?
 What Is a Connected Environment?
 What Is a Disconnected Environment?
 What Is the ADO.NET Object Model?
 What Is the DataSet Class?
 What Is the .NET Data Provider?
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What Is ADO.NET?
ADO.NET is a data access technology. It provides:
 A set of classes, interfaces, structures, and
enumerations that manage data access from within
the .NET Framework
 An evolutionary, more flexible successor to ADO
 A system designed for disconnected environments
 A programming model with advanced XML support
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What Is a Connected
Environment?
 A connected
environment is one in which users are
constantly connected to a data source
 Advantages:

Environment is easier to secure
 Concurrency is more easily controlled
 Data is more likely to be current than in other scenarios
 Disadvantages:

Must have a constant network connection
 Scalability
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What Is a Disconnected Environment?


In a disconnected environment, a subset of data from
a central data store can be copied and modified
independently, and the changes merged back into
the central data store
Advantages




You can work at any time that is convenient for you, and can
connect to a data source at any time to process requests
Other users can use the connection
A disconnected environment improves the scalability and
performance of applications
Disadvantages


Data is not always up to date
Change conflicts can occur and must be resolved
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What Is the ADO.NET Object Model?
DataSet
.NET Data Provider
Connection
Transaction
DataAdapter
SelectCommand
DataTableCollection
DataTable
DataRowCollection
InsertCommand
DataColumnCollection
Parameters
UpdateCommand
ConstraintCollection
DataReader
DeleteCommand
Command
DataRelationCollection
XML
Database
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What Is the .NET Data Provider?
Database
Connection
Manages the connection
to a database
Executes a query command
on the database
Command
Exchanges data between
the data set and the database
DataAdapter
DataReader
Provides efficient access to a
stream of read-only data
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Creating an Application That Uses
ADO.NET to Access Data
 How
to Specify the Database Connection
 How to Specify the Database Command
 How to Create the DataAdapter Object
 How to Create a DataSet Object
 How to Bind a DataSet to a DataGrid
 How to Use the Data Wizards in Visual Studio
.NET
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How to Specify the Database
Connection
 Use
the Connection object to:

Choose the connection type
 Specify the data source
 Open the connection to the data source
 Use
the connection string to specify all of the options
for your connection to the database, including the
account name, database server, and database name
string connectionStr = @"Data Source=localhost;
Integrated Security=SSPI; Initial Catalog=northwind";
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How to Specify the Database
Command
string commandStr=@"SELECT CustomerName,
CompanyName FROM Customers";

Create a string containing SQL statements


Remember that Verbatim strings can make this much easier!
Examples of SQL statements:

SELECT * FROM Customers

SELECT CustomerName FROM Customers

SELECT * FROM Customers WHERE Country = 'Mexico'
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How to Create the DataAdapter
Object
DataSet
Data source
DataAdapter
DataTable
Fill
Update
DataAdapter
DataTable
Fill
Update
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What Is the DataSet Class?
 DataSets
consist of one
or more tables and
relations
DataSet
Tables
Table
 Loaded
from one or more
data adapters
 Created as you work
 Loaded from XML
 Loaded from other
DataSets
Columns
Column
Constraints
Constraint
Rows
 Tables
contain columns,
constraints, and rows
Row
Relations
 All
Relation
Object
are collections!
Collection
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How to Bind a DataSet to a
DataGrid
To bind programmatically
DataGrid dataGrid1 = new DataGrid();
sqlDataAdapter1.Fill(dataSet1, "Customers");
sqlDataAdapter2.Fill(dataSet1, "Orders");
dataGrid1.DataSource = dataSet1;
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Changing Database Records
 How
to Access Data in a DataSet Object
 How to Update a Database in ADO.NET
 How to Create a Database Record
 How to Update a Database Record
 How to Delete a Database Record
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How to Access Data in a DataSet
Object
DataRow
objects
DataTable
objects
DataColumn
objects
DataColumn
objects
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How to Update a Database in
ADO.NET
Client
Server
DataAdapter
DataSet
Data
Database
Fill
DataTable
Update
Data
InsertCommand
UpdateCommand
DeleteCommand
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How to (Manually) Create a Database
Record
Create a new row that matches the table schema
DataRow myRow = dataTable.NewRow();
Add the new row to the dataset
dataTable.Rows.Add( myRow );
Update the database
sqlDataAdapter1.Update( dataSet );
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How to (Manually) Delete a Database
Record
 Delete
the row from the dataset
dataTable.Rows[0].Delete();
 Update
the database
dataAdapter.Update(dataSet);
 Accept
the changes to the dataset
dataSet.AcceptChanges();
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Data Reader




Data Readers manage the stream of results from a
SELECT statement or Stored Procedure
Data Readers are read only
Data Readers only move forwards through the data –
they cannot go backwards
No other database operation can be performed while
a data reader is open
19
Using a DataReader with a SELECT
Statement
string queryString =
"SELECT FirstName, LastName FROM dbo.Employees";
//Create the command objects
SqlCommand com = new SqlCommand(queryString, conn);
//Call the command's ExecuteReader method
SqlDataReader dr = com.ExecuteReader();
//Loop through the datareader to output the employee names
while (dr.Read())
{
listBox1.Items.Add(dr.GetString(0) + " " +
dr.GetString(1));
}
20
Using a DataReader to call a Stored
Procedure
//Create the command object and set its properties
SqlCommand com = new SqlCommand();
com.Connection = conn;
com.CommandText = "CustOrderHist";
com.CommandType = CommandType.StoredProcedure;
//Create the parameter object and add it to the command's
collection
SqlParameter param =
new SqlParameter("@CustomerID", SqlDbType.NVarChar, 5);
param.Value = txtID.Text;
com.Parameters.Add(param);
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Creating a Two Tier Application
 Create
the data tier
Create
a new class library project
Create a class to represent a business entity, say
customers
Add methods that access the database, using ADO.Net
Add properties that expose attributes, say name, phone …
 Create
the presentation tier
Create
a new Windows Application project
Add a reference to the above data project
Create an object from class
Use the object’s properties to populate controls on a form
Use the object’s methods to access the database
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New Features of ADO.NET 2.0
 Multiple
active result sets
One
connection can host more than one result set
Reduces number of connections on a database
 Asynchronous
operations
Begin
a data access operation, continue with other tasks,
and then later end the original operation
 Batch
updates
Update
multiple rows in one batch
Use the UpdateBatchSize property of the DataAdapter
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Visual Studio Wizards and Designers
Data
Source Configuration Wizard
TableAdapter Configuration Wizard
TableAdapter Query Configuration Wizard
Preview Data Dialog Box
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Lab 17: Accessing Data Using ADO.NET
Exercise 1: Retrieving Data into a Data
Set
 Exercise 2: Updating the Database
from a Data Set
 Exercise 3: Retrieving Data with a
Data Reader
 Exercise 4: Calling a Stored Procedure

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