net data access

.NET Data Access

台南市教育局網路中心在職教師校務行政系統程式開發進階班行政網路組asp@mail.tn.edu.tw

Design Goals for ADO.NET

• Leverage Current ADO Knowledge • Support the N-Tier Programming Model • Integrate XML Support

Why ADO.NET?ADO vs. ADO.NET

• ADO– Connected access– Physical data model– RecordSet based data– RecordSet is ‘one’ table

• > 1 table requires a database JOIN

• Data is “flattened”: lose relationships

– COM/COM+ data types– Data via COM marshalling– Blocked by firewalls

(DCOM, binary)

• ADO.NET– Disconnected access– Logical data model– The DataSet based data– DataSet is multi-table

• > 1 table or source does not require a JOIN

• Relationships remain: navigation is relational

– XML schema Data types – No data type conversions required

– XML is plaintext: ‘Firewall friendly’

DataSetDataSet

ADO.NET Architecture()

System.DataSystem.Data

System.Data.OleDbSystem.Data.OleDb System.Data.SQLTypesSystem.Data.SQLTypesSystem.Data.SqlClientSystem.Data.SqlClient

.NET Data Providers.NET Data Providers

ADO.NET Architecture(2)• XML and ADO.NET• ADO.NET Components

.NET Data Provider

• Retrieve data from a data source and reconcile changes made to it with the data source

• The link between data source and application

• Two Providers out of the box:– .NET SQL Data Provider: SqlClient– .NET OLE DB Data Provider: OleDb

ADO.NET Data ProviderCore Classes

ConnectionConnection

CommandCommand

Data ReaderData Reader

Data AdapterData Adapter

System.Data.<Provider>System.Data.<Provider>Connect to data sourceConnect to data source

Execute Command Execute Command against data sourceagainst data source

Reads a forward-only read-Reads a forward-only read-only stream of data from a only stream of data from a

data sourcedata source

Populates a DataSet and Populates a DataSet and resolves updates with data resolves updates with data

sourcesource

Connection Class• Represent a unique session with a data source• Create, open, close a connection to a data source• Functionality and methods to perform transactions• Connection example:

String conStr = "Provider=Microsoft.Jet.OLEDB.4.0;" +String conStr = "Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=NWIND_RW.MDB"; "Data Source=NWIND_RW.MDB";OleDbConnection aConn = new OleDbConnection(conStr);OleDbConnection aConn = new OleDbConnection(conStr);aConn.Open();aConn.Open();

// Execute Queries using OleDbCommand Class

aConn.Close();aConn.Close();

Connection

• OleDbConnection Provider=MSDAORA; Data Source=ORACLE8i7; User ID=OLEDB; Password=OLEDB

Provider=Microsoft.Jet.OLEDB.4.0; Data Source=c:\bin\LocalAccess40.mdb;

Provider=SQLOLEDB;Data Source=MySQLServer;Integrated Security=SSPI; • SqlConnection user id=sa;password=aU98rrx2;initial catalog=northwind;data source=mySQLServer;Connect Timeout=30

Command Class• Represents a query to execute on the data

source• Methods of interest:

– ExecuteNonQuery: Executes a SQL statement that doesn’t return any rows

– ExecuteReader: Returns a DataReader– ExecuteScalar: Executes the query and returns

the first column of the first row

String SqlStr = “INSERT INTO Customers (CustId,FName,Lname) ;” +String SqlStr = “INSERT INTO Customers (CustId,FName,Lname) ;” +““Values (‘Matt’,’Stephen’)”;Values (‘Matt’,’Stephen’)”;

SqlCommand myCommand = new SqlCommand(SqlStrSqlStr , myConnection);myCommand.Connection.Open(); myCommand.ExecuteNonQuery(); myConnection.Close();

DataAdapter Class • Bridge between the DataSet and the data store• Means to modify the DataSet and data source• Properties of Interest: DeleteCommand, InsertCommand,

SelectCommand, UpdateCommand• TableMappings: Maps source and DataTable• Inherits methods from DbDataAdapter class

– public virtual int Fill(DataSet,”Tablename”); – public virtual int update(DataSet,”Tablename”);

Data Store DataSetDataAdapter

DataReader• Forward-only data access• “Lightweight” programming model

– Less overhead than using Command• Instantiated by the Command class Execute method• Ties up the Command until it is finished reading• Methods to retrieve data:

– By index and optionally column type: GetString, GetInt32, and so on

– Read: Advances reader to next record

DataReader Sample

// Code for creating the Connection “Conn” not shownString myQuery = “SELECT * FROM Customers”;String myQuery = “SELECT * FROM Customers”;Conn.Open();Conn.Open();OleDbCommand myCmd = new OleDbCommand( myQuery, Conn );OleDbCommand myCmd = new OleDbCommand( myQuery, Conn );// Declare the DataReader...OleDbDataReader myDataReader;OleDbDataReader myDataReader;

// Instantiate the DataReader with ExecuteReader(...) ...myDataReadermyDataReader = = myCmd.ExecuteReader();myCmd.ExecuteReader();

// Always call Read before accessing data. while(myDataReader.Read()) while(myDataReader.Read()) {{

Console.WriteLine(myDataReader.GetString(0));Console.WriteLine(myDataReader.GetString(0));}}// Always Close the reader and the connection when donemyDataReader.Close();myDataReader.Close();Conn.Close();Conn.Close();

System.Data Principal Classes

DataSetDataSet

DataTableDataTable

DataRowDataRow

DataColumnDataColumn

DataRelationDataRelation

DataViewDataView

Contains the ‘main’ classes of Contains the ‘main’ classes of ADO.NETADO.NET

In-memory cache of databaseIn-memory cache of database

In-memory cache of database tableIn-memory cache of database table

Used to manipulate a row in a Used to manipulate a row in a DataTableDataTable

Used to define the columns in a Used to define the columns in a DataTableDataTable

Used to relate two Used to relate two DataTablesDataTables to each to each otherother

Used to create a view on a Used to create a view on a DataSetDataSet

System.DataSystem.Data

DataSet Tables

DataTable

System.Data: DataSet Overview

Relations

DataRelation

DataRelation

DataRow(s)

DataColumn

Constraint(s)

DataTable

DataTable

DataView

DataView

System.Data: DataSet• An in-memory cache of data from a data source via

DataAdapter• XML used to read and write data and schema• Common way to represent and manipulate data

– Universal data container– Not just for use with databases

• Logical or physical representation of data, depending on: – The query/result set– Whether DataTables and Relations exist

• Designed to be disconnected from the data source– Connect, execute query, disconnect

System.Data: DataTable• May be mapped to a physical table in the data

source• Can be related to one another through

DataRelations• Optimistic concurrency / locking• Properties of Interest:

– Columns: Returns DataColumnCollection of DataColumns

– Rows: Returns DataRow objects as a DataRowCollection

– Constraints: Returns the table’s ConstraintCollection

System.Data: DataSet & DataTable• Create a DataTable and add it to a DataSet

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

// Create DataTable object: “Customers”.DataTable dt = new DataTable( “Customers” );DataTable dt = new DataTable( “Customers” );

// Create and add columns to the table// 1. Explicitly create and Add a DataColumnDataColumn dc = new DataColumn( “CustID”, typeof(Int16) );DataColumn dc = new DataColumn( “CustID”, typeof(Int16) );dt.Columns.Add( dc );dt.Columns.Add( dc );

// 2. Implicitly Create and Add columns (DataColumn).dt.Columns.Add( “First_Name”, typeof(String) );dt.Columns.Add( “First_Name”, typeof(String) );dt.Columns.Add( “Last_Name”, typeof(String) );dt.Columns.Add( “Last_Name”, typeof(String) );

// Add the DataTable object to the DataSetds.Tables.Add( dt );ds.Tables.Add( dt );

如何存取資料庫• ADO .NET 資料存取模型

– 資料庫連線 (Connection)• SqlConnection 與 OleDbConnection

– 執行 SQL 語法 (Commands)• SqlCommand 與 OleDbCommand

– ExecuteNonQuery ( 不傳回資料列 )– ExecuteScalar ( 傳回單一列資料 )– ExecuteReader ( 傳回多列資料 )

– 取得資料• DataReader• DataAdapter 與 DataSet

• 使用資料庫連線的步驟– OleDbConnection conn = new OleDbConnection() ;

– conn.ConnectionString =

"Provider=Microsoft.Jet.OLEDB.4.0; User ID=Admin; Password=123;

Data Source=C:\Northwind.mdb" ;

– conn.Open() ;

– conn.Close() ;

如何使用資料庫連線– 建立資料庫連線物件– 設定連線字串

– 開啟資料庫連線– :

– 關閉資料庫連線

• SqlConnection– conn.ConnectionString =

"User ID=sa; Password=; Server=localhost;Database=Northwind"

;

• OleDbConnection– conn.ConnectionString =

"Provider=SQLOLEDB; User ID=sa; Password=;

Data Source=localhost; Initial Catalog=Northwind" ;

Connection

– 只能夠連接 Microsoft SQL Server– 效能最佳化– 需引用 System.Data.SqlClient

– 可以透過 OLE DB 連接不同的資料庫– 應用範圍最廣– 需引用 System.Data.OleDb– 一樣可以連接 Microsoft SQL Server

Command • SqlCommand 與 OleDbCommand

• 支援多種 SQL 命令– DCL : GRANT, REVOKE, DENY

– DDL : CREATE, ALTER, DROP

– DML : SELECT, INSERT, DELETE, UPDATE

– 其它 : Stored Procedure, CURSOR, …

• 允許加入參數 (Parameters)

• 執行非查詢式 SQL 語法– SqlCommand cmd = new

SqlCommand("update… where OrderID=@ID", conn) ;

– SqlParameter param = new SqlParameter("@ID", typeof(int)) ;

– param.Value = 12 ;

– cmd.Parameters.Add(param) ;

– int rowEffects = cmd.ExecuteNonQuery() ;

執行 SQL 語法– 建立一個 Command 物件

– 建立參數物件– 設定參數值– 將參數加入 Command 物件– 執行 SQL 語法

• 執行查詢式 ( 單筆記錄 ) SQL 語法– string sql = "select cid from… where OrderID=@ID" ;

– SqlCommand cmd = new SqlCommand(sql, conn) ;

– SqlParameter param = new SqlParameter("@ID", typeof(int)) ;

– param.Value = 12 ;

– cmd.Parameters.Add(param) ;

– int myCID = (int) cmd.ExecuteScalar() ;

如何執行 SQL 語法– 建立一個 Command 物件– 建立參數物件– 設定參數值– 將參數加入 Command 物件– 執行 Command 並取得結果

• 執行查詢式 ( 多筆記錄 ) SQL 語法– string sql = "select PName, Qty from MyOrders" ;

– SqlCommand cmd = new SqlCommand(sql, conn) ;

– SqlDataReader dr = cmd.ExecuteReader() ;

– while ( dr.Read() ){

string pname = dr.GetString(0) ;int qty = dr.GetInt32(1) ;Console.WriteLine("{0}, {1}", pname, qty) ;

}

如何處理多筆記錄– 建立一個 Command 物件– 執行 Command 並取得 DataReader

– 讀取下一筆記錄 ( 如果 true 表示有資料 ){

取得第一個欄位取得第二個欄位

}

• 執行 Stored Procedure– SqlCommand cmd = new SqlCommand() ;

– cmd.Connection = conn ;

– cmd.ComandText = "DeleteOrder" ;

– cmd.CommandType = CommandType.StoredProcedure ;

– cmd.Parameters.Add("@ID", orderID) ;

– int rowEffects = cmd.ExecuteNonQuery() ;

如何執行 Stored Procedure

– 建立一個 Command 物件– 設定使用連線– 設定命令名稱– 設定 CommandType

– 建立參數– 執行 Stored Procedure

Data Access Layer Calling stored procedures

Dim sqlconn As SqlConnection = New SqlConnection(connectionstring)aDim sqlcomm As SqlCommand = New SqlCommand()sqlcomm.CommandType = CommandType.StoredProceduresqlcomm.CommandText = "DemoProc“

‘Open Connectionsqlconn.Open()sqlcomm.Connection = sqlconn

'Create parameterssqlcomm.Parameters.Add(New SqlParameter("@input1", SqlDbType.Int))sqlcomm.Parameters.Add(New SqlParameter("@input2", SqlDbType.Int))sqlcomm.Parameters.Add(New SqlParameter("@output1",

SqlDbType.Int)).Direction = ParameterDirection.Output

‘Set Parameter Valuessqlcomm.Parameters.Item("@input1").Value = 123sqlcomm.Parameters.Item("@input2").Value = 456sqlcomm.ExecuteNonQuery()

‘Access OutputResponse.write (sqlComm.Parameters.Item(“@output1”).Value.ToString())

WebForms 控制項資料繫結<%@ Import Namespace="System.Data.SqlClient" %><html><head><script language="C#" runat=server>

public void Page_Load(Object sender, EventArgs args) {

// 建立資料庫連線，並取得 DataReaderSqlConnection cnn = new SqlConnection("server=localhost;uid=sa;");conn.Open();SqlCommand cmd = new SqlCommand("select * from customers", conn);SqlDataReader dr = cmd.ExecuteReader();

// 將資料來源繫結到控制項dgCustomers.DataSource = dr;dgCustomers.DataBind(); }

</script></head><body><asp:DataGrid id="dgCustomers" runat="server"/>

</body></html>

自訂 Data Provider• ADO .NET 共有那些 Data Provider

– SQL Data Provider– OLE DB Data Provider– ODBC Data Provider ( 外掛 )– Oracle Data Provider ( 未來 )

SelectCommandSelectCommand

InsertCommandInsertCommand

UpdateCommandUpdateCommand

DeleteCommandDeleteCommand

DataAdapter 與 DataSet• DataSet 與資料庫之間透過 DataAdapter 進行存取動作

DataAdapterDataAdapter

DataSetDataSet資資料料庫庫 Update Update

Fill Fill

• 透過 DataAdapter 取得 DataSet 資料– SqlCommand cmd = new SqlCommand() ;

cmd.Connection = conn ;cmd.ComandText = "select * from Customers" ;

– SqlDataAdapter da = new SqlDataAdapter() ;

– da.SelectCommand = cmd;

– DataSet ds = new DataSet("Customers") ;

– da.Fill(ds) ;

如何取得 DataSet

– 建立一個 Command用來執行 SELECT 語法

– 建立 DataAdapter 物件– 設定 SelectCommand

– 建立一個 DataSet 物件– 使用 DataAdapter 物件的 Fill 方法

填滿 DataSet

– SqlDataAdapter da = new SqlDataAdapter("select * from Customers",

conn) ;

DataSet 的結構• DataSet 可以包含多個表格 (Table) ，組成 Tables 集合

DataSetDataSet

TablesTables

Tables[0]Tables[0]Tables[1]Tables[1]Tables[2]Tables[2]Tables[3]Tables[3]

::::::::::

DataTableDataTable

RowsRows

Rows[0]Rows[0]Rows[1]Rows[1]Rows[2]Rows[2]

::::::::

DataRowDataRow

• 使用 Tables[ 表格號碼 ] 或 Tables[" 表格名稱 "] 來引用 Tables 中的任何一個表格。(Tables.Count 可以取得表格數目 )

• 每一個 DataSet 中的表格都是一個 DataTable 物件• DataTable 可以包含多筆資料列 (Row) ，組成 Rows 集合• 使用 Rows[ 列號碼 ] 來引用 Tables 中的任何一個表格。(Rows.Count 可以取得資料總筆數 )

• Rows 集合中的每一筆資料記錄都是一個 DataRow 物件

AB(04)2222-2222男王小明血型電話性別姓名

3210

DataRowDataRow rowrow = = dsds..TablesTables[0].[0].RowsRows[[33];];stringstring name = name = rowrow[[00];];stringstring phone = phone = rowrow[["" 電話電話 ""];];

• 透過欄位號碼或欄位名稱來存取 DataRow 的資料• 每一個 DataRow ( 每一筆記錄 ) 中包含了多個欄位

• 使用 foreach 迴圈瀏覽 DataSet 資料foreach(DataRow cust in ds.Tables[0].Rows){

Console.WriteLine("\n 客戶 : {0}", cust["Name"]);foreach(DataRow ord in cust.GetChildRows("odr")){

Console.Write(" 訂單編號 : {0}", ord["id"]);Console.Write("\t 數量 :{1}\n", ord["qty"]);

}}

• 使用 for 迴圈瀏覽 DataSet 資料for(int c=0;c < ds.Tables[0].Columns.Count; c++) { DataColumn dc = ds.Tables[0].Columns[c] ;

Console.Write("{0}\t", dc.ColumnName) ;}for(int r = 0;r < ds.Tables[0].Rows.Count;r++) {

string cName = ds.Tables[0].Rows[r][" 客戶名稱 "] ;string cAddress = ds.Tables[0].Rows[r][" 地址 "] ;Console.WriteLine("\n{0}\t{1}", cName, cAddress) ;

}

如何瀏覽 DataSet 中的資料

Data, XML, And .NETXML Recap

• XML declaration• Document element• Elements• Attributes• Text content• Namespaces

<?xml version="1.0"?><?xml version="1.0"?><employees xmlns="urn:…"><employees xmlns="urn:…">

<employee id="123"><employee id="123"> <name>Philips</name><name>Philips</name> <salary>145000</salary><salary>145000</salary> </employee></employee> … …</employees></employees>

.NET XML Classes Namespaces and Classes

XmlReaderXmlReader

System.Xml namespaceSystem.Xml namespace

XmlWriterXmlWriter

XmlNavigatorXmlNavigator

XmlDocumentXmlDocument

XmlElementXmlElement

XmlAttributeXmlAttribute

etc.etc.

System.Xml.XPathSystem.Xml.XPath• Plus…

System.Xml.XslSystem.Xml.Xsl

XPath engineXPath engine

XSLT transformsXSLT transforms

.NET XML Classes Reading XML Data

• Use XmlReader class– Fast, forwards-only, read-only cursor– “Pull” model (not the “push” model of SAX)

• XmlReader is an abstract class– Several concrete

subclasses

XmlReaderXmlReader{ Abstract class }{ Abstract class }

XmlTextReaderXmlTextReaderRead a text-based Read a text-based

streamstream

XmlNodeReaderXmlNodeReaderRead an in-memory Read an in-memory

DOM treeDOM tree

.NET XML Classes Using XmlReader

• Example

• Capabilities– Pull nodes you want, skip those you don't– Get detailed node information– Get typed data

XmlReader reader;XmlReader reader;reader = new XmlTextReader("MyFile.xml");reader = new XmlTextReader("MyFile.xml");while(reader.Read())while(reader.Read()){ { …process nodes… } }

.NET XML Classes Writing XML Data

• Use XmlWriter

• Alternatively…– Create content using XmlDocument– Serialise data using XmlWriter

XmlWriterXmlWriter

XmlTextWriterXmlTextWriter XmlNodeWriterXmlNodeWriter

XmlWriter writer = new XmlTextWriter(…);XmlWriter writer = new XmlTextWriter(…);writer.WriteStartDocument();writer.WriteStartDocument();writer.WriteStartElement("name", "Mike");writer.WriteStartElement("name", "Mike");

.NET XML Classes Using XPath

• XPath maps an XML document to a tree of nodes

• Use XPath expressions to identify, select, and manipulate nodes in an XML hierarchy– Use location paths

to select nodes– XPath operators and functions

.NET XML Classes XML .NET Support for XPath

• XmlNavigator class provides XPath support

• Evaluate XPath expressions

• Select nodes using XPath

XmlNavigator nav;XmlNavigator nav;nav = new DocumentNavigator(document);nav = new DocumentNavigator(document);

nav.Evaluate("count(//employee)");nav.Evaluate("count(//employee)");

nav.Select("//employee[salary > 75000]");nav.Select("//employee[salary > 75000]");

.NET XML Classes Using XSLT

XML XML documentdocument

XSLT XSLT style sheetstyle sheet

++ XSLT XSLT processorprocessor

HTML document HTML document (XML-conformant)(XML-conformant)

XML XML documentdocument

XSLT XSLT style sheetstyle sheet

++ XSLT XSLT processorprocessor

XML document XML document (different grammar)(different grammar)

.NET XML Classes XML .NET Support for XSLT

• XslTransform class represents an XSLT style sheet

// Load style sheetXslTransform xsl = new XslTransform();XslTransform xsl = new XslTransform();xsl.Load("MyStylesheet.xsl");xsl.Load("MyStylesheet.xsl");

// Perform transformationxsl.Transform(aNavigator, xsl.Transform(aNavigator, null, null, anXmlWriter); anXmlWriter);

SyncSync

XML and ADO.NET Unified Architecture

DataReaderDataReader

SqlData-SqlData-ReaderReader

OleDbData-OleDbData-ReaderReader

Controls,Controls,Designers,Designers,

Code-gen, etc.Code-gen, etc.

DataSetDataSet

XmlReaderXmlReader

XmlText-XmlText-ReaderReader

XmlNode-XmlNode-ReaderReader

XSL/T, X-Path,XSL/T, X-Path,Validation, etc.Validation, etc.

XmlData-XmlData-DocumentDocument

DataAdapterDataAdapter

SqlData-SqlData-AdapterAdapter

OleDbData-OleDbData-AdapterAdapter