ADO .NET – part II
August 2004[ Marmagna Desai]
CONTENTS ADO vs ADO .NET ADO .NET – Managed providers Connecting to Database
SqlConnection Selecting Database
SqlCommand SqlDataReader
Inserting Data SqlCommand
Datasets Selecting Data Updating Data
Conclusion
ADO vs ADO .net
Ultimate goal of ADO and ADO.net is same: Providing data access API.
Though there are many differences. ADO relies on COM ADO.net relies on “managed-providers”
defined by CLR
ADO vs ADO .net ……[cont]
Main Differences:
ADO ADO.NET
Connection Model Connection Oriented Model is used mostly.
Disconnected Model is used: Messeage-like Model.
Disconnected Access Provided by RecordSet Provided by DataAdapter and Dataset
Data Representation One Recordset for one Table
One Dataset for many interrelated tables with relationships
Data Exchange Binary Mode – Firewall Problem
Use XML and XSD schema types are fully supported
XML Support Limited Robust Support
ADO vs ADO .net ……[cont]Connection Model: ADO:
Client application needs to be connected always to data-server while working on the data.
These results in open connections for long time and thus data can not be accessed in parallel.
ADO .NET Client disconnects connection immediately the data is processed.
This will cache data at client side to achieve better performance.
Hence ADO .net creates “disconnected version of RecordSet object
ADO vs ADO .net ……[cont]
Data Representation:
Recordsets are generated one per table. This does not support hierarchical structure of data access. It will be programmer’s responsibility to define relationships among different recordsets.
Rercordsets can not support data accessing from multiple sources.
Above limitations are resolved by implementation of Dataset objects in ADO.net mode
ADO vs ADO .net ……[cont]
Data Passing:
ADO objects communicate in binary mode hence it will be really difficult to pass data across firewalls.
ADO .net use XML for passing data
ADO .net Managed Providers
ADO .net provides following three classes DBConnection DBCommand DBDataReader
These classes are never used directly. The inherited set of classes called “managed providers” are used for different functionalities of data access
ADO .net Managed Providers
These are the different providers Provider optimized for SQL 7 OLE – DB provider A generic ODBC provider Provider for Oracle
These providers gathers information on various data sources and how to interact with them E.g.
SQL data provider uses private protocol (tabular data stream) to provide information and access methods on SQL server.
Connecting to Database
Following methods are very similar to ADO. They are connection oriented and hence leave open connection while retrieving the data from source. SQL managed provider contains the class called SqlConnection. This class is used to connect to the sql database.
Code:
[ Please see next slide]
Code…..
Dim connStr as String = “server=localhost;uid=uid;pwd=pwd;database=northwind;"Dim conn as New SqlConnection (connStr)Conn.Open()“Access Data RecordsConn.Close()
This is very similar to ADO program. Only the SqlConnection will be replaced with ADODB.Connection.
Selecting Data
SqlCommand class is defined in ADO .net to provide different functionalities like insert,update,delete etc. on selected database.
It is similar to ADODB.Command class in ADO.
SqlCommand retrieves and place data on objects called SqlDataReader
SqlCommand does this using ExecuteReader() method.
[Please see next slide for Code]
CodeDim conn As SqlConnection = Nothing
Tryconn = New SqlConnection(connStr)
Dim cmd As New SqlCommand("Select StateCode, " & "StateName From States", conn)
conn.Open()Dim reader As SqlDataReader = _
cmd.ExecuteReader(CommandBehavior.CloseConnection)Me.ddRegion.DataSource = readerMe.ddRegion.DataBind() Me.ddRegion.Items.Insert(0, New ListItem("Select One:", ""))Catch exp As ExceptionlblOutput.Text = "Error occurred: " + exp.MessageFinallyIf (conn.State <> ConnectionState.Closed) Then conn.Close() End Try
Explanation
A connection is made using SqlConnection
SqlCommand is used to construct a query
ExecuteReader is used to generate SqlDataReader object
Bind data to DropDownList Server name ddRegion
Inserting Data
SqlCommand can be used to perform insert,delete,update etc. operations on data. ExecuteNonQuery method is used for this purpose.This method does not allow results to return to the database.
[Please see code in next slide]
CodeDim conn As New SqlConnection(connStr)Dim cmd As New SqlCommand("CustInsert", conn)
cmd.CommandType = CommandType.StoredProcedurecmd.Parameters.Add("@CustomerID",
Me.txtCustomerID.Text)cmd.Parameters.Add("@Name", Me.txtName.Text)cmd.Parameters.Add("@Company", Me.txtCompany.Text)cmd.Parameters.Add("@Title", Me.txtTitle.Text)cmd.Parameters.Add("@Address", Me.txtAddress.Text)cmd.Parameters.Add("@City", Me.txtCity.Text)cmd.Parameters.Add("@Region",
Me.ddRegion.SelectedValue)cmd.Parameters.Add("@Zip", Me.txtZip.Text)
Code ….[cont]
Tryconn.Open()cmd.ExecuteNonQuery() lblOutput.Text = "Your information was successfully
saved!"Catch exp As ExceptionlblOutput.Text = "An error occurred:" + exp.MessageFinally 'Ensure connection is closedIf (conn.State <> ConnectionState.Closed) Then
conn.Close()End Try
Datasets
Datasets are new to ADO .net.
It access data in Disconnected in maner
It stores data in-memory and process it.
Datasets….[cont]
Following are main features Datasets does not interact with data source directly. Data adapter is used to fill this gap. : SqlDataAdapter class SqlDataAdapter class provides functionalies such as insert, delete
and update. SqlDataAdapter also provides method called Fill() which is used
to fill up the Dataset. Once dataset is filled with data, it can define relationships among
gathered data from different source. Dataset uses XML to transmit data among different components. Different views of data stored in dataset can be created using
dataview calss.
Code
Following code shows how to query database using SqlDataAdapter and fill the Dataset. Dim conn As SqlConnection = NothingTryconn = New SqlConnection(connStr)‘Create DataAdapterDim da As New SqlDataAdapter("Select StateCode, " & _"StateName From States", conn)‘Create DataSetDim ds As New DataSet‘Fill DataSetda.Fill(ds, "States")
Code …cont
‘Access a DataTable in the DataSet and create a bindable viewDim view As DataView = ds.Tables(0).DefaultViewMe.ddRegion.DataSource = viewMe.ddRegion.DataBind()Me.ddRegion.Items.Insert(0, New ListItem("Select One:", ""))Catch exp As ExceptionlblOutput.Text = "Error occurred: " + exp.MessageFinallyIf (conn.State <> ConnectionState.Closed) Then conn.Close()End Try
Conclusion
Basically ADO .net adds following extended capabilities to ADO. Disconnected modeling Relational Database query and in-memory storage Hierarchical structure of data XML based transmission of data among components
These additional features makes ADO .net considerable advancement in Microsoft Technology
Q?THANKS!!