ADO.Net and Stored Procedures By Radhika Malladi

Introduction ADO.Net : database API, used for managed applications It consists of a set of classes Integrates with XML It provides components for creating distributed, data-sharing applications It is used to connect to data source for retrieving, updating and manipulating data.

Introduction cont. Data providers are used to connect to the database, to execute commands and retrieving results ADO.Net provides two data providers SQL Server .Net provider – Interfaces MicrosoftSQLServer with Managed applications(System.data.SqlClient) OLE DB .Net provider – Interfaces databases with UnManaged OLE DB providers(System.data.OleDb)

Design Goals ADO.Net is designed to meet the following goals: Leverage current ADO knowledge Support N-tier programming model ("Any number of levels arranged above another, each serving distinct and separate tasks.“) Done by using Data Set because Data Set works well with all providers Integrating XML

ADO.Net Components Two main components: Data Set – disconnected architecture of ADO.Net .Net data provider components – for data manipulation and read-only access to data Connection – to make connections to database Command – access to database commands Data Reader – provides stream of data from data source Data Adapter – bridge between Data Set object and data source

Architecture

.Net provider Components Connection : SqlConnection conn = new SqlConnection     ("server=localhost;database=a1;uid=sa;pwd="); SqlConnection conn = new SqlConnection     ("server=xyz\malladi;database=a1;uid=sa;pwd="); SqlConnection conn = new SqlConnection     ("server=xyz\malladi;database=a1;uid=sa;pwd=;min pool size=10;max pool size=50;connect timeout=10;Integrated Security = false;Pooling = true;"); OleDbConnection conn = new OleDbConnection      ("provider=sqloledb;data source=localhost;OLE DB Services=-2" +     "initial catalog=a1;user id=sa;password=");

.Net Components cont. Command: SqlCommand cmd = new SqlCommand ("select * from users", conn); Properties: CommadTimeout , CommandText Methods: ExecuteNonQuery() – This returns number of rows affected Ex: Insert, Delete, Update (no return values) ExecuteScalar() – single row, single column values Ex: count, min, max, sum, avg etc and to retrive BLOBs ExecuteReader()

.Net Components cont. Data Reader: SqlDataReader reader = cmd.ExecuteReader (); ExecuteReader() – obtains query results quickly for read-only. Ex: Select reader.close(); Methods: GetName – retrieve field names GetValue – retrieve field values(returns obj) GetOrdinal – converts field name into numeric index

.Net Components cont. Data Adapter: SqlDataAdapter adapter = new SqlDataAdapter ("select * from users",     "server=localhost;database=a1;uid=sa;pwd=");

Example (ExecuteReader) SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Inetpub\\wwwroot\\Assign2\\App_Data\\a2.mdf;Integrated Security=True;User Instance=True"); try { con.Open(); SqlCommand cmd = new SqlCommand("select role from users where username = '" + TextBox1.Text.Trim() + "' and password = '" + TextBox2.Text.Trim() + "'", con); SqlDataReader dr = cmd.ExecuteReader(); while (dr.Read()) role = dr.GetString(dr.GetOrdinal("role")); break; } catch (SqlException ex) Response.Write(ex.Message); finally con.Close();

Example (ExecuteScalar) SqlConnection connection = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=c:\\inetpub\\wwwroot\\Assign2\\App_Data\\a2.mdf;Integrated Security=True;User Instance=True"); try{ connection.Open(); StringBuilder builder = new StringBuilder(); builder.Append("select count (*) from users where username = \'"); builder.Append(username); builder.Append("\' and cast (rtrim (password) as varbinary) = cast (\'"); builder.Append(password); builder.Append("\' as varbinary)"); SqlCommand command = new SqlCommand(builder.ToString(),connection); int count = (int)command.ExecuteScalar(); return (count > 0); } catch (SqlException) { return false; } finally { connection.Close(); }

Example (ExecuteNonQuery) SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Inetpub\\wwwroot\\Assign2\\App_Data\\a2.mdf;Integrated Security=True;User Instance=True"); try { con.Open(); SqlCommand cmd = new SqlCommand("insert into users (username,password,role)values('" + TextBox6.Text.Trim() + "','" + TextBox7.Text.Trim() + "','" + DropDownList1.SelectedValue + "')", con); int noofrows = cmd.ExecuteNonQuery(); if (noofrows != 0) Response.Write("user created successfully"); } catch (SqlException ex) { Response.Write(ex.Message); } finally { con.Close(); }

Data Set and Data Adapters Set based access – captures query into memory and supports traversal through result set This has 2 classes Data Set : in-memory database Data Adapter : bridge between Data Set and data source Perform database queries create DataTables containing query results Capable of writing changes made to data tables back to database

Data Adapter Two versions: SqlDataAdapter and OleDbDataAdapter Main Methods of Data Adapter are Fill and Update Namespace – system.data.common.DbDataAdapter

Data Adapter cont. Fill: SqlDataAdapter adapter = new SqlDataAdapter ("select * from users",     "server=localhost;database=a1;uid=sa;pwd="); DataSet ds = new DataSet (); adapter.Fill (ds, “users"); Update : adapter.Update (table); Builder for Insert, Update, Delete: SqlCommandBuilder builder = new SqlCommandBuilder (adapter);

Data Set DataSet object – supports disconnected, distributed data with ADO.Net Can be used with multiple and differing data sources It represents complete set of data like related tables, constraints and relationships among tables

Data Set cont.

Data Set cont. DataTable Collection : contains collection of tables DataRelationCollection: contains relationships of tables ExtendingProperties: Property Collection where customized information can be placed Ex: Date/Time when data is generated

Example to insert records SqlDataAdapter adapter = new SqlDataAdapter ("select * from titles", "server=localhost;database=pubs;uid=sa;pwd="); DataSet ds = new DataSet (); adapter.Fill (ds, "Titles"); // Create a new DataRow DataTable table = ds.Tables["Titles"]; DataRow row = table.NewRow (); // Initialize the DataRow row["title_id"] = "JP1001"; row["title"] = "Programming Microsoft .NET"; row["price"] = "59.99"; row["ytd_sales"] = "1000000"; row["type"] = "business"; row["pubdate"] = "May 2002"; // Add the DataRow to the DataTable table.Rows.Add (row);

Examples to select records DataRow[] rows = table.Select ("title_id = 'JP1001'"); DataRow[] rows = table.Select ("price < 10.00"); DataRow[] rows = table.Select ("pubdate >= '#1/1/2000#'"); DataRow[] rows = table.Select ("state in ('ca', 'tn', 'wa')"); DataRow[] rows = table.Select ("state like 'ca*'"); DataRow[] rows = table.Select ("isnull (state, 0) = 0"); DataRow[] rows = table.Select ("state = 'tn' and zip like '37*'");

Example to update records SqlDataAdapter adapter = new SqlDataAdapter ("select * from titles", "server=localhost;database=pubs;uid=sa;pwd="); DataSet ds = new DataSet (); adapter.Fill (ds, "Titles"); DataRow[] rows = table.Select ("ytd_sales > 10000"); foreach (DataRow row in rows) row["price"] = (decimal) row["price"] + 10.00m;

Example to delete records SqlDataAdapter adapter = new SqlDataAdapter ("select * from titles", "server=localhost;database=pubs;uid=sa;pwd="); DataSet ds = new DataSet (); adapter.Fill (ds, "Titles"); DataRow[] rows = table.Select ("ytd_sales < 10000 OR isnull (ytd_sales, 0) = 0"); foreach (DataRow row in rows) row.Delete ();

Example for Updating the database SqlDataAdapter adapter = new SqlDataAdapter ("select * from titles", "server=localhost;database=pubs;uid=sa;pwd="); SqlCommandBuilder builder = new SqlCommandBuilder (adapter); DataSet ds = new DataSet (); adapter.Fill (ds, "Titles"); // Insert a record DataTable table = ds.Tables["Titles"]; DataRow row = table.NewRow (); row["title_id"] = "JP1001"; row["title"] = "Programming Microsoft .NET"; row["price"] = 59.99m; row["ytd_sales"] = 1000000; row["type"] = "business"; row["pubdate"] = new DateTime (2002, 5, 1); table.Rows.Add (row); // Update the database adapter.Update (table);

Stored Procedures User defined command added to a database Executes faster as they are already complied Improves performance ADO.Net supports stored procedures An Example of stored procedure is..

CREATE PROCEDURE proc_TransferFunds @Amount money, @From char (10), @To char (10) AS BEGIN TRANSACTION UPDATE Accounts SET Balance = Balance @Amount WHERE Account_ID = @From IF @@ROWCOUNT = 0 BEGIN ROLLBACK TRANSACTION RETURN END UPDATE Accounts SET Balance = Balance + @Amount WHERE Account_ID = @To IF @@ROWCOUNT = 0 BEGIN RETURN END COMMIT TRANSACTION GO

catch (SqlException ex) { // TODO: Handle the exception } SqlConnection conn = new SqlConnection     ("server=localhost;database=mybank;uid=sa;pwd="); try {      conn.Open ();      SqlCommand cmd = new SqlCommand ("proc_TransferFunds", conn);     cmd.CommandType = CommandType.StoredProcedure;      cmd.Parameters.Add ("@amount", 1000);     cmd.Parameters.Add ("@from", 1111);      cmd.Parameters.Add ("@to", 2222);     cmd.ExecuteNonQuery (); } catch (SqlException ex) {     // TODO: Handle the exception } finally {     conn.Close (); }

Transacted Commands Example SqlConnection conn = new SqlConnection ("server=localhost;database=mybank;uid=sa;pwd="); try { conn.Open (); // Debit $1,000 from account 1111 SqlCommand cmd = new SqlCommand ("update accounts set balance = balance -1000 where account_id = '1111'", conn); cmd.ExecuteNonQuery (); // Credit $1,000 to account 2222 cmd.CommandText = "update accounts set balance = " + "balance + 1000 where account_id = '2222'"; cmd.ExecuteNonQuery (); } catch (SqlException ex) { // TODO: Handle the exception } finally { conn.Close (); }

Transacted Commands Example SqlTransaction trans = null; SqlConnection conn = new SqlConnection     ("server=localhost;database=mybank;uid=sa;pwd="); try {     conn.Open ();     // Start a local transaction     trans = conn.BeginTransaction (IsolationLevel.Serializable);      // Create and initialize a SqlCommand object     SqlCommand cmd = new SqlCommand ();     cmd.Connection = conn;     cmd.Transaction = trans;      // Debit $1,000 from account 1111      cmd.CommandText = "update accounts set balance = balance - 1000 where account_id = '1111'";      cmd.ExecuteNonQuery ();     // Credit $1,000 to account 2222      cmd.CommandText = "update accounts set balance = " +         "balance + 1000 where account_id = '2222'";      cmd.ExecuteNonQuery ();      // Commit the transaction (commit changes)      trans.Commit (); } catch (SqlException) {     // Abort the transaction (roll back changes)  if (trans != null) trans.Rollback (); } finally {     conn.Close (); }

Parameterized Commands Example SqlConnection conn = new SqlConnection ("server=localhost;database=mybank;uid=sa;pwd="); try { conn.Open (); // Create and initialize a SqlCommand object SqlCommand cmd = new SqlCommand("update accounts set balance = balance + @amount " + "where account_id = @id", conn); cmd.Parameters.Add ("@amount", SqlDbType.Money); cmd.Parameters.Add ("@id", SqlDbType.Char); // Debit $1,000 from account 1111 cmd.Parameters["@amount"].Value = -1000; cmd.Parameters["@id"].Value = "1111"; cmd.ExecuteNonQuery (); // Credit $1,000 to account 2222 cmd.Parameters["@amount"].Value = 1000; cmd.Parameters["@id"].Value = "2222"; cmd.ExecuteNonQuery (); } catch (SqlException ex) { // TODO: Handle the exception } finally { conn.Close (); }

Programming Microsoft .Net by Jeff Prosise References ADO.Net by Alex Homer Programming Microsoft .Net by Jeff Prosise http://msdn2.microsoft.com/en-us/library/e80y5yhx(VS.71).aspx http://www.ondotnet.com/pub/a/dotnet/excerpt/progvisbasic_ch08/index.html

Thank you