Direct Data Access, Data Binding. Content Direct Data Access Data Binding Muzaffer DOĞAN - Anadolu...

Web Server ProgrammingDirect Data Access, Data Binding

ContentDirect Data AccessData Binding

Muzaffer DOĞAN - Anadolu University 2

Direct Data Access


Important Note!!!Last week, you learned how to connect to

databases using built-in controls.Use them in your applications whenever

possible.If you sure that you need to connect to

database manually, follow the instructions explained in this class.


Direct Data Access – Querying1. Create Connection, Command, and

DataReader objects2. Use the DataReader to retrieve information

from the database, and display it in a control

3. Close your connection4. Send the page to the user


Updating, Inserting, Deleting1. Create new Connection and Command

objects2. Execute the Command with the appropriate

SQL statement


Direct Data Access with ADO.NET


ADO.NET Data Provider ClassesSQL Server OleDB (Access)

Connection SqlConnection OleDbConnection

Command SqlCommand OleDbCommand

DataReader SqlDataReader OleDbDataReader

DataAdapter

SqlDataAdapter

OleDbDataAdapter


Use OracleConnection, OracleCommand, etc. for Oracle data providers

Use OdbcConnection, OdbcCommand, etc. for ODBC data providers

Namespace ImportsImport following namespaces for SQL Server:

using System.Data;using System.Data.SqlClient;

Import following namespaces for Access:using System.Data;using System.OleDb;


Connecting Access DatabaseOleDbConnection conn = new OleDbConnection();

conn.ConnectionString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Survey.mdb";

conn.Open();

// Database operations will be here...

conn.Close();


Connecting SQL Server ExpressSqlConnection conn = new SqlConnection();

conn.ConnectionString = @"Data Source=.\SQLEXPRESS; AttachDbFilename=|DataDirectory|\Survey.mdf; Integrated Security=True;User Instance=True";

conn.Open();

// Database operations will be here...

conn.Close();


How to Obtain Connection StringsUse SqlDataSource or AccessDataSource

objects to connect to the database and copy the connection strings into your code

http://www.connectionstrings.com shows many connection string options


Storing the Connection StringWrite the connection string into

connectionString section of web.config file:<configuration> <connectionStrings> <add name="Pubs" connectionString="Data

Source=localhost;Initial Catalog=Pubs;Integrated Security=SSPI"/>

</connectionStrings> ...</configuration>


Retrieving the Connection Stringstring connectionString =

WebConfigurationManager.ConnectionStrings["Pubs"].ConnectionString;


Execute CommandCommand object has several methods

starting with the "Execute" string:ExecuteNonQuery(): Used for queries that

don't return any records (e.g. Update, Insert, Delete queries)

ExecuteReader(): Used for queries that return one or more records (e.g. Select query)

ExecuteScalar(): Used for queries that return one or more records but this method returns only the first column of the first row (suitable for obtaining number of records, maximum value of a column)


The DataReaderAllows you to quickly retrieve all your resultsUses a live connection and should be used

quickly and then closedCan retrieve only one record at a timeSupports fast-forward-only and read-only

access to the results (previous record cannot be reached)

Provides better performance than the DataSet


The DataReaderCreate a DataReader by ExecuteReader

method of the Command objectRetrieve the record by the Read() method of

the DataReader objectTo retrieve the next record, use Read()

method againIf next record is successfully read, the Read()

method returns trueSo, continue reading until the Read() method

returns false


The DataReaderOleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Survey.mdb");

OleDbCommand cmd = new OleDbCommand("SELECT * FROM UserInfo", conn);

conn.Open();OleDbDataReader reader = cmd.ExecuteReader();while (reader.Read()){ Label1.Text += reader["FirstName"] + "<br />";}reader.Close();conn.Close();


ExecuteScalar ExampleOleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Survey.mdb");

OleDbCommand cmd = new OleDbCommand("SELECT MAX(FavoriteNumber) FROM UserInfo", conn);

conn.Open();

int maxfav = (int)cmd.ExecuteScalar();

conn.Close();


ExecuteNonQuery ExampleOleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=|DataDirectory|\Survey.mdb");

OleDbCommand cmd = new OleDbCommand("DELETE * FROM UserInfo WHERE UserID=5", conn);

conn.Open();

int affectedRowNumber = cmd.ExecuteNonQuery();

conn.Close();


Data Binding


Data BindingYou can use the DataSet or the DataReader to retrieve

rows of information, format them individually, and add them to an HTML table on a web page

Conceptually, this isn’t too difficult. However, it still requires a lot of repetitive code to move through the data, format columns, and display it in the correct order

Repetitive code may be easy, but it’s also error-prone, difficult to enhance, and unpleasant to read

Fortunately, ASP.NET adds a feature that allows you to skip this process and pop data directly into HTML elements and fully formatted controls. It’s called data binding


Data BindingThe basic principle of data binding is this: you tell

a control where to find your data and how you want it displayed, and the control handles the rest of the details.

ASP.NET data binding works in one direction only. Information moves from a data object into a control. Then the data objects are thrown away, and the page is sent to the client. If the user modifies the data in a data-bound control, your program can update the corresponding record in the database, but nothing happens automatically.


Types of ASP.NET Data BindingSingle-Value, or "Simple", Data Binding

Single-value data binding allows you to take a variable, a property, or an expression and insert it dynamically into a page

Single-value binding also helps you create templates for the rich data controls

Repeated-Value, or "List", BindingAllows you to display an entire table (or just a

single field from a table)


Using Data BindingTo use single-value binding, you must insert a

data binding expression into the markup in the .aspx file (not the code-behind file).

To use repeated-value binding, you must set one or more properties of a data control.

Once you specify data binding, you need to activate it. You accomplish this task by calling the DataBind() method of the control.

Alternatively, you can bind the whole page at once by calling the DataBind() method of the current Page object.


A Simple List Binding ExampleArrayList fruit = new ArrayList();fruit.Add("Kiwi");fruit.Add("Mango");fruit.Add("Blueberry");fruit.Add("Apricot");fruit.Add("Banana");lstItems.DataSource = fruit;lstItems.DataBind(); // orthis.DataBind();


ReferencesBeginning ASP.NET 3.5 in C# 2008: From

Novice to ProfessionalVisual Studio and MSDN Help


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