Direct Data Access, Data Binding

Content Direct Data Access Data Binding Muzaffer DOĞAN - Anadolu University2

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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. Muzaffer DOĞAN - Anadolu University4

Direct Data Access – Querying 1. Create Connection, Command, and DataReader objects 2. Use the DataReader to retrieve information from the database, and display it in a control 3. Close your connection 4. Send the page to the user Muzaffer DOĞAN - Anadolu University5

Updating, Inserting, Deleting 1. Create new Connection and Command objects 2. Execute the Command with the appropriate SQL statement Muzaffer DOĞAN - Anadolu University6

Direct Data Access with ADO.NET Muzaffer DOĞAN - Anadolu University7

ADO.NET Data Provider Classes SQL ServerOleDB (Access) ConnectionSqlConnectionOleDbConnection CommandSqlCommandOleDbCommand DataReaderSqlDataReaderOleDbDataReader DataAdapterSqlDataAdapterOleDbDataAdapter Muzaffer DOĞAN - Anadolu University8 Use OracleConnection, OracleCommand, etc. for Oracle data providers Use OdbcConnection, OdbcCommand, etc. for ODBC data providers

Namespace Imports Import following namespaces for SQL Server: using System.Data; using System.Data.SqlClient; Import following namespaces for Access: using System.Data; using System.OleDb; Muzaffer DOĞAN - Anadolu University9

Connecting Access Database OleDbConnection conn = new OleDbConnection(); conn.ConnectionString Data Source=|DataDirectory|\Survey.mdb"; conn.Open(); // Database operations will be here... conn.Close(); Muzaffer DOĞAN - Anadolu University10

Connecting SQL Server Express SqlConnection conn = new SqlConnection(); conn.ConnectionString Source=.\SQLEXPRESS; AttachDbFilename=|DataDirectory|\Survey.mdf; Integrated Security=True;User Instance=True"; conn.Open(); // Database operations will be here... conn.Close(); Muzaffer DOĞAN - Anadolu University11

How to Obtain Connection Strings Use SqlDataSource or AccessDataSource objects to connect to the database and copy the connection strings into your code shows many connection string options Muzaffer DOĞAN - Anadolu University12

Storing the Connection String Write the connection string into connectionString section of web.config file:... Muzaffer DOĞAN - Anadolu University13

Retrieving the Connection String string connectionString = WebConfigurationManager. ConnectionStrings["Pubs"].ConnectionString; Muzaffer DOĞAN - Anadolu University14

Execute Command Command 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) Muzaffer DOĞAN - Anadolu University15

The DataReader Allows you to quickly retrieve all your results Uses a live connection and should be used quickly and then closed Can retrieve only one record at a time Supports fast-forward-only and read-only access to the results (previous record cannot be reached) Provides better performance than the DataSet Muzaffer DOĞAN - Anadolu University16

The DataReader Create a DataReader by ExecuteReader method of the Command object Retrieve the record by the Read() method of the DataReader object To retrieve the next record, use Read() method again If next record is successfully read, the Read() method returns true So, continue reading until the Read() method returns false Muzaffer DOĞAN - Anadolu University17

The DataReader OleDbConnection conn = new 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"] + " "; } reader.Close(); conn.Close(); Muzaffer DOĞAN - Anadolu University18

ExecuteScalar Example OleDbConnection conn = new Source= |DataDirectory|\Survey.mdb"); OleDbCommand cmd = new OleDbCommand("SELECT MAX(FavoriteNumber) FROM UserInfo", conn); conn.Open(); int maxfav = (int)cmd.ExecuteScalar(); conn.Close(); Muzaffer DOĞAN - Anadolu University19

ExecuteNonQuery Example OleDbConnection conn = new Source= |DataDirectory|\Survey.mdb"); OleDbCommand cmd = new OleDbCommand("DELETE * FROM UserInfo WHERE UserID=5", conn); conn.Open(); int affectedRowNumber = cmd.ExecuteNonQuery(); conn.Close(); Muzaffer DOĞAN - Anadolu University20

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Data Binding You 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 Muzaffer DOĞAN - Anadolu University22

Data Binding The 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. Muzaffer DOĞAN - Anadolu University23

Types of ASP.NET Data Binding Single-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", Binding Allows you to display an entire table (or just a single field from a table) Muzaffer DOĞAN - Anadolu University24

Using Data Binding To 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. Muzaffer DOĞAN - Anadolu University25

A Simple List Binding Example ArrayList fruit = new ArrayList(); fruit.Add("Kiwi"); fruit.Add("Mango"); fruit.Add("Blueberry"); fruit.Add("Apricot"); fruit.Add("Banana"); lstItems.DataSource = fruit; lstItems.DataBind(); // or this.DataBind(); Muzaffer DOĞAN - Anadolu University26

References Beginning ASP.NET 3.5 in C# 2008: From Novice to Professional Visual Studio and MSDN Help Muzaffer DOĞAN - Anadolu University27