ADO.NETData Access with Microsoft .NET

Andreas Schabus

Academic Relations

Microsoft Österreich GmbH

andreas.schabus@microsoft.com

http://blogs.msdn.com/msdnat

Session Targets

• What is ADO.NET and how does it work?

• What are the differences to traditional, connected

data access methods?

• What are DataReaders and DataSets and when to use

what?

The Role Of ADO.NET

• Data access framework

– Database independent

– All types of applications

– Successor of class ADO

• Developed in .NET

– Language independent

– Application type independent

• Database independent

Changing Requirements

Different application types

• High scale web

– Always connected (?)

– Extreme performance

• Offline Smart Client

– Definitely not connected

High scale

web

Offline

Smart Client

Connected vs. Disconnected

• Disconnected model– Save resources

– Enable offline

• Connected model– Increase performance

– Easier programming model

• Solution: compromise– As few connections as possible

– Offline object / programming model

ADO.NET ARCHITECTURE

Understanding fundamental classes

The ADO.NET Model

• Get your data– Connect and retrieve

– Static forward / read only cursor

– No locking

• Work disconnected– XML support

– Similar to record set

• Update your data– Connect and execute SQL

ADO.NET Architecture

• Managed Provider

– Access to data source

– Data source classes

• Connection

• Command, Parameter

• DataReader

• Offline classes

– DataTable

– DataSet (n DataTables)

Data

Source

Application

Windows Forms, Web Forms,

Web Services

ADO .NET

KlassenDataset

Data

Reader

Managed Provider

SQL Server OLE DB…

ADO.NET Object Model

Connection

Command

Parameter

DataReader

Transaction

DataAdapter

DataSet

DataTable

DataColumn

DataRow

Constraint

DataRelation

.NET Data Provider

Database Support

• Basically independent– System.Data

– System.Data.Common

• Data providers out-of-the-box– System.Data.SqlClient

– System.Data.OracleClient

– System.Data.Odbc

– System.Data.OleDb

• Custom providers

Connection Class

• Base interfaces / classes

– IDbConnection

• Primary tasks

– Connect to database

– Start transactions

SqlConnection cn;cn = new SqlConnection("server=localhost;database=pubs");

cn.Open()'... Some tasks...

cn.Close()

Commands And Parameters

• Command base interface

– IDbCommand

• Primary tasks

– Encapsulate SQL command

• Text or Stored Procedure

– Manage query-parameters

– Execute SQL command

string strSQL = "SELECT * FROM titles"SqlCommand cmd = new SqlCommand(strSQL, Conn)

SqlDataReader reader = cmd.ExecuteReader()

Commands And Parameters

• Parameter base interface

– IDataParameter

• Primary tasks

– Parse & verify parameter

– Convert to database type

string strSQL = "SELECT * FROM titles WHERE name LIKE @val“;SqlCommand cmd = new SqlCommand(strSQL, Conn);

cmd.Parameters.Add("@val", SqlTypes.VarChar, 20);cmd.Parameters["@val„].Value = "Programming%„;

SqlDataReader reader = cmd.ExecuteReader();

DataReader Class

• Base interface

– IDataReader

• Primary task

– Read data from result-set

– Forward-only, read-only performance

SqlDataReader rdr As SqlDataReader = cmd.ExecuteReader();

While(rdr.Read()){

Console.WriteLine(rdr["OrderID“]);

Console.WriteLine(rdr[1]);

Console.WriteLine(rdr.GetString[2]);

}

rdr.Close();

Simple data access

THE OFFLINE MODEL

DataTables and DataSets

DataTable Class

• In-memory snapshot– Single table

– Scrollable, updateable

– Data source independant

• Schema information– Columns, column-types

– Rule constraints

• User data– Snapshot of database data

– DataRow class

DataSet Class

• Data container, too

– Multiple tables

– Relations between tables

• Schema information

– List of tables

– Relations between tables

• DataRelation

• Verified offline

• Enables navigation

Function of the DataAdapter

DataSet

Connection

DataAdapter

SelectCommand

InsertCommand

UpdateCommand

DeleteCommand

• Datencontainer

• verwendet intern XML

Mapping:

DataReader DataSet

DataAdapter Class

• Base interface, class

– IDataAdapter

– DataAdapter

• Primary tasks

– Execute SQL (read & update)

– Result-set DataTable / DataSet

SqlConnection cn = new SqlConnection("server=localhost;...")SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM titles", cn)

DataSet ds = new DataSet();da.Fill(ds, "Titles")

Processing Steps (1/2)

• Define Command

– Eventually create command-object

• Create DataAdapter

– Requires command & connection

• Create & fill DataTable / DataSet

– Instantiate DataSet

– Call DataAdapter.Fill()

– Optional – DataAdapter.FillSchema()

Processing Steps (2/2)

• Change data offline– Add rows (DataTable.NewRow())

– Delete rows (DataRow.Delete())

– Change rows

Row["Fieldname"] = value

• Update in database– Call DataAdapter.Update()

– All changes in DataTable / DataSet

– Changed records, only

DataAdapter und DataSets

Read via Fill() & FillSchema()

Change existing rows

SqlConnection cn = new SqlConnection("server=localhost;...");SqlAdapter da = new SqlDataAdapter("SELECT * FROM titles", cn);

DataSet ds = new DataSet();da.Fill(ds, "Titles");

DataRow row;

ds.Tables["Titles„].Rows(0)["name„] = "Neuer Name„;row = ds.Tables["Titles„].Rows(2)row.BeginEdit()row["name„] = "Advanced ADO.NET"row["Verlag„] = "Microsoft Press"row.EndEdit() 'or row.CancelEdit()

DataAdapter und DataSets

Add new rows

Delete existing rows

DataRow newRow;newRow = ds.Tables["titles„].NewRow();

newRow["name„] = "Applied ADO.NET Programming;newRow["Verlag„] = "Microsoft Press„;

ds.Tables.Rows.Add(newRow)

string filter = "PubDate <= '1/1/1995'„;

DataRow[] delRow();delRow = ds.Tables["titles„].Select(filter);

foreach( DataRow dr in delRow){dr.Delete()

]

DataAdapter and DataSets

• Creating necessary commands

– Via Designer (empfohlen)

– Dynamically: SqlCommandBuilder

• Via Get????Command() method

• Primary key in DataTable (FillSchema() !!)

• Execute the update

SqlDataAdapter da = new SqlDataAdapter("SELECT * FROM titles", cn);

SqlCommandBuilder cmdBuilder;cmdBuilder = new SqlCommandBuilder(da);

da.Update(ds)

DataView Class

• Like database view

– But offline

– On DataTable contents

• Primary tasks

– Filtering, sorting

– Intended for binding to controls!!

'...DataSet ds = new DataSet();da.Fill(ds, "Titles");

DataView dv = new DataView(ds.Tables["Titles"]);DataView dv = ds.Tables["Titles"].DefaultView;

Now you know…

• …what ADO.NET is and it works.

• …what are the differences between connected and

disconnected data access.

• …what DataReaders and DataSets are and how the

can be used?

Bibliographie

CodePlex. (21.02.2008). Microsoft SQL Server Community & Samples. Retrieved

March 09, 2008, from http://codeplex.com/SqlServerSamples

DevASP.Bet. Retrieved March 09, 2008, from

http://www.devasp.net/net/search/display/category74707.html

Microsoft Corporation. .NET Framework Developer's Guide: ADO.NET.

Retrieved March 09, 2008, from http://msdn2.microsoft.com/en-

us/library/e80y5yhx.aspx

Microsoft Corporation. Gewusst wie: Binden eines Windows Forms-

Steuerelements an ein Factoryobjekt. Retrieved March 09, 2008, from

http://msdn2.microsoft.com/de-de/library/at23yw2h(vs.80).aspx

Mössenböck, H., Beer, W., Prähofer, H., & Wöß, A. (09.02.2007). Application

Development with C# and .NET. Retrieved March 06, 2008, from

http://dotnet.jku.at/courses/dotnet/