Deccansoft Software Services - MS.NET 4.5 Database Programming using ADO.NET Agenda

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1 Agenda 1. Prerequisite Knowledge of SQL Queries 2. Introduction and Evolution of ADO.NET 3. Understanding the Role of Managed Provider and ADO.NET Objects 4. Installing Required Software - Sql Server and Management Studio 5. Connecting to database and Connection Pooling 6. Performing Insert, Update and Delete Operations 7. Fetching Data from database Executing Select Statements 8. How to implement Login facility with database 9. Use of Multiple Active Result Sets 10. Parameterized Prepared Statements 11. Inserting Image into Database table. 12. Executing Stored Procedure 13. Using Transaction 14. Asynchronous Execution of Queries 15. Writing Provider Independent Code 16. Writing Common Code for Execution of Stored Procedures 17. Quick Overview of all ADO.NET objects 1

2 Evolution of ADO.NET Structured Query Language = DDL + DML + DCL + DTL Data Definition Language = Create, Alter, Drop Data Manipulation Language = Insert, Delete, Update, Select Data Control Language = Grant, Revoke Data Transaction Language = Commit, Rollback, SavePoint Note: Knowledge of writing SQL Statements is expected prerequisite for this chapter. Native Drivers 1. Available in the form of Win32 Library 2. Specific to a given database 3. Different API for every new database ODBC Drivers 1. Available in the form of Win32 Libraries 2. Database independent API 3. Same API implemented differently for every database DAO / RDO Object Models 1. Object based approach for operating with Database 2. DAO Data Access Objects were used for MS.Access 3. RDO Remote Data Access Objects were used for remote databases like Oracle and SQL server. 4. Used only for datbase backends 5. Cannot be used with Excel, CSV, etc.. backends ADO (ActiveX Data Objects) 1. Common Object Model for all databases 2. Uses Ole-Db Providers instead of ODBC 3. It s a compact and efficient Object Model 4. Can be used for all types of backends including databases, excel files, csv files, s etc 2

3 ADO.NET Architecture and Role of Managed Provider ADO.NET Architecture Role of Managed Provider: It is a.net component implementing certain standard set of interfaces provided by Microsoft, for a specific type of backend. Following are the four managed providers which are built in along with MS.NET Framework. Provider Namespace API Data Source Description Name prefix ODBC System.Data.Odbc Odbc Data Sources with an ODBC interface. Normally older data bases. OleDb System.Data.Oledb OleDb Data Sources that expose an OleDb interface, i.e. Access or Excel. Oracle System.Data.OracleClient Oracle For Oracle Databases. SQL Server System.Data.SqlClient Sql For interacting with Microsoft SQL Server. More Managed Providers Oracle.ManagedDataAccess.Client is the Namespace for Managed provider provided by Oracle. MySql.Data.MySqlClient by MySql and downloaded from Important Objects in Managed Provider (ADO.NET Objects): 1. Connection: Connection object encapsulates the functionally of establishing a communication path over the sockets. 2. Command: Command Object can be used for execution of any type of Sql Statement including Stored Procedures. 3. Data Reader: Used to fetch data returned from result of execution of Select statement. 4. Data Adapter: Used to create DataSet which is disconnected model of operating with database. 3

4 Software Requirements / Installations If using Express Edition of Visual Studio: 1. Go to 2. Select and download SQL Server Express with Tools (with LocalDB, Includes the database engine and SQL Server Management Studio Express) 3. You can down load either 32 or 64-bit based on your OS (Right click on Computer Properties to find if your OS is 32-bit or 64 bit). If using VS.NET Professional or Ultimate, you will already have SQL Server Express installed on your machine. If required only SQL Server Management Studio Express can be installed and even that is not needed as most of the things can be done from VS.NET itself. Establish Connection with Database and Connection Pooling Steps to create Database and Tables In VS.NET : Creating a new Database Goto ServerExplorer Right Click on Data Connections Create New Sql Server Database Server Name as.\sqlexpress New Database name as MSNETDemoDB Creating table in Server Explorer: Emp (EmpId, EmpName, EmpSalary) table in backend. EmpId Int, PrimaryKey and also set Identity = True in Property of EmpId field EmpName Varchar(50) - AllowNull = False (Uncheck) EmpSalary Money AllowNull = True (Check) Step 1. Add to the project a file by name App.config (Application Configuration File) Edit App.config <configuration> <connectionstrings> <add name="csmsnetdb" connectionstring="server=.\sqlexpress;database=msnetdb;integrated Security=True"/> </connectionstrings> </configuration> Code: C# Step 2. Add Reference to System.Configuration (Project Reference.NET Tab Select System. Configuration OK) Step 3. Add to the project a class by name Helper (Helper.cs) Helper class: class Helper public static string ConnectionString 4

5 get return System.Configuration.ConfigurationManager.ConnectionStrings["csMSNETDB"].ConnectionString; Code: C# Step 4: To Establish Connection To test a connection Add a button on the form with name: Test Connection and ID: btntestconnection. Double click on btntestconnection and add the following code: private void btntestconnection_click(object sender, EventArgs e) SqlConnection con = new SqlConnection(); con.connectionstring = Helper.ConnectionString; try //executing commands... MessageBox.Show("Connection now open", "Status"); finally if (con.state == ConnectionState.Open) con.close(); Connection string formats for SQL Server 1. "Data Source=.\sqlexpress;Initial Catalog=MSNETDemoDb;Integrated Security=True" 2. Data Source=.\sqlexpress;Database= MSNETDemoDb; User Id=sa; Password=dss" 3. "Server=.\sqlexpress;Database= MSNETDemoDb;uid=sa;pwd=dss" Important: Data Source or Server are same Initial Catalog or Database are same User Id or uid are same Password or pwd are same We should either give Intergrated Security or uid / pwd 5

6 The ConnectionString format depends on the managed provider used for connecting to database. : to get connectionstring for all database. What is Connection Pooling? In.Net, Connections are Pooled. We can have by default up to 100 simultaneous connections without closing but obviously we have to close every connection Opened only then it can be reused from Pool i.e. keeps the connection with the database open for the short period of time. The Connection Pooling can be customized by setting appropriate parameters in ConnectionString of Connection Object and this cannot be done for Oledb and ODBC managed providers. For two or more connection objects to share a common connection in the pool their connection strings must match. <connectionstrings> <add name="msdemocs" connectionstring="server=.\sqlexpress;database=msnetdemodb;integrated Security=true; max pool size=200;pooling=false"/> </connectionstrings> Performing Insert, Update and Delete Operations Steps to execute any SQL Statement 1. Create a Connection 2. Create a Command 3. Bind the Command to Connection 4. Initialize Command with SQL Statement to execute 5. Open the Connection 6. Execute the Command 7. Close the Connection SQLCommand Methods for execution of Commands: 1. int ExecuteNonQuery(): Used for execution of those statements which do not return any data from backend to frontend. return 2. Object ExecuteScalar() - Used for execution of statements which return only one value.- return Object 3. SqlDataReader ExecuteReader() - Used for execution of statements which return multiple rows and columns i.e. a set of records. 6

7 To insert a record in the table (btninsert_click) Insert button click event: Private Sub btninsert_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btninsert.click Dim con As SqlConnection = New SqlConnection(Helper.ConnectionString) Dim cmd As SqlCommand = New SqlCommand '3. Bind the Command to Connection cmd.connection = con Dim name As String = txtname.text.replace("'", "''") Dim salary As Decimal = Decimal.Parse(txtSalary.Text) cmd.commandtext = ("Insert into Emp(EmpName, EmpSalary) Values('" _ + (name + ("'," _ + (salary + ")")))) MessageBox.Show(cmd.CommandText) cmd.commandtype = CommandType.Text '5. Open the Connection con.open() '6. Execute the Command cmd.executenonquery() MessageBox.Show ("Inserted...") '7. To Fetch the last inserted EmpId cmd.commandtext = txtid.text = cmd.executescalar.tostring '8. Close the Connection con.close() End Sub Code: VB Insert button click event: 7

8 private void btninsert_click(object sender, EventArgs e) //1. Create a Connection SqlConnection con = new SqlConnection(Helper.ConnectionString); //2. Create a Command SqlCommand cmd = new SqlCommand(); //3. Bind the Command to Connection cmd.connection = con; //4. Initialize Command with SQL Statement to execute string name = txtname.text.replace("'", "''"); decimal salary = decimal.parse(txtsalary.text); cmd.commandtext = "Insert into Emp(EmpName, EmpSalary) Values('" + name + "'," + salary + ")"; MessageBox.Show(cmd.CommandText); cmd.commandtype = CommandType.Text; //5. Open the Connection //6. Execute the Command cmd.executenonquery(); MessageBox.Show("Inserted..."); //7. To Fetch the last inserted EmpId cmd.commandtext = //** txtid.text = cmd.executescalar().tostring(); //8. Close the Connection con.close(); Code: C# Note: Over a given connection if an insert statement is executed on a table with Identity Column, the backend sql-server for that connection initializes a parameter by with the value of Identity column for the last inserted record. Update button click event: Private Sub btnupdate_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btnupdate.click Dim con As SqlConnection = New SqlConnection(Helper.ConnectionString) Dim cmd As SqlCommand = New SqlCommand '3. Bind the Command to Connection cmd.connection = con Dim name As String = txtname.text.replace("'", "''") Dim salary As Decimal = Decimal.Parse(txtSalary.Text) 8

9 cmd.commandtext = ("Update Emp set EmpName='" _ + (txtname.text + ("', EmpSalary=" _ + (txtsalary.text + (" where EmpId=" + txtid.text))))) MessageBox.Show(cmd.CommandText) cmd.commandtype = CommandType.Text '5. Open the Connection con.open() '6. Execute the Command cmd.executenonquery() MessageBox.Show("Updated...") '8. Close the Connection con.close() End Sub Code: VB Update button click event private void btnupdate_click(object sender, EventArgs e) //1. Create a Connection SqlConnection con = new SqlConnection(Helper.ConnectionString); //2. Create a Command SqlCommand cmd = new SqlCommand(); //3. Bind the Command to Connection cmd.connection = con; //4. Initialize Command with SQL Statement to execute string name = txtname.text.replace("'", "''"); decimal salary = decimal.parse(txtsalary.text); cmd.commandtext = "Update Emp set EmpName='" + txtname.text + "', EmpSalary=" + txtsalary.text + " where EmpId=" + txtid.text; MessageBox.Show(cmd.CommandText); cmd.commandtype = CommandType.Text; //5. Open the Connection //6. Execute the Command cmd.executenonquery(); MessageBox.Show("Updated..."); //8. Close the Connection con.close(); Code: C# 9

10 Delete button click event Private Sub btndelete_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btndelete.click Dim con As SqlConnection = New SqlConnection(Helper.ConnectionString) Dim cmd As SqlCommand = New SqlCommand cmd.connection = con Dim name As String = txtname.text.replace("'", "''") Dim salary As Decimal = Decimal.Parse(txtSalary.Text) cmd.commandtext = "Update Emp set EmpName='" + txtname.text + "', EmpSalary=" + txtsalary.text + " where EmpId=" + txtid.text MessageBox.Show(cmd.CommandText) cmd.commandtype = CommandType.Text con.open() cmd.executenonquery() MessageBox.Show("Updated...") con.close() End Sub Code: VB Delete button click event private void btndelete_click(object sender, EventArgs e) SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand(); cmd.connection = con; string name = txtname.text.replace("'", "''"); decimal salary = decimal.parse(txtsalary.text); cmd.commandtext = "Update Emp set EmpName='" + txtname.text + "', EmpSalary=" + txtsalary.text + " where EmpId=" + txtid.text; MessageBox.Show(cmd.CommandText); cmd.commandtype = CommandType.Text; cmd.executenonquery(); MessageBox.Show("Updated..."); con.close(); Code: C# 10

11 Fetching Data from Database Select Statement SqlDataReader When Select or similar type of sql statement is executed a new cursor (memory area in backend) is created on the back end. This Cursor contains primary key or indexed key of the table on which the statement is executed for the records which have qualified the condition in the where clause of the select statement. It also has a pointer, which is by default positioned at BOF. The cursor and pointers functionality is encapsulated by the DataReader object created in the front end. Using this object, we can move the pointer in the forward direction getting one record from backend into the frontend at the time. The cursor managed by Data Reader is read-only and forward-only To Get all the records of the Employee table: Private Sub btngetallemps_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btngetallemps.click Dim con As New SqlConnection con.connectionstring = Helper.ConnectionString Dim cmd As New SqlCommand() cmd.connection = con cmd.commandtype = CommandType.Text cmd.commandtext = "Select * from Emp" Dim dr As SqlDataReader con.open() dr = cmd.executereader() Dim str As String = "" While (dr.read()) str &= dr(0).tostring() & vbtab Dim indname As Integer indname = dr.getordinal("empname") str &= dr.getstring(indname) & vbtab Dim indsalary As Integer indsalary = dr.getordinal("empsalary") If (dr.isdbnull(indsalary)) Then str &= vbcrlf Else str &= dr.getdecimal(indsalary) & vbcrlf End If End While dr.close() : con.close() MsgBox(str) End Sub 11

12 Code: VB To Get all the records of the Employee table: private void btngetallemps_click(object sender, EventArgs e) SqlConnection con = new SqlConnection(); con.connectionstring = Helper.ConnectionString; SqlCommand cmd = new SqlCommand("Select * from Emp", con); cmd.commandtype = CommandType.Text; SqlDataReader dr = cmd.executereader(); string str = ""; while (dr.read()) //Read return false when the pointer on the cursor has reached EOF str += dr[0].tostring() + "\t"; int indname = dr.getordinal("empname"); str += dr.getstring(indname) +"\t"; int indsalary = dr.getordinal("empsalary"); if (dr.isdbnull(indsalary)) str += "----\n"; else str += dr.getdecimal(indsalary) + "\n"; dr.close(); con.close(); MessageBox.Show(str); Code: C# Note: It is recommended to use the GetX (X is datatype for example GetInt32()) methods for fetching data from the datareader because here we don t have to cast unlike in case of using indexed property which returns Object and has to be casted Example: To Verify Username and Password Validity Create a table: UserProfile(PKUserId, UserName, Password) Login click event private void btnlogin_click(object sender, EventArgs e) 12

13 SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand(); cmd.connection = con; cmd.commandtext = "Select PKUserId, Password From UserProfile where Username='" + txtusername.text + "'"; SqlDataReader dr = cmd.executereader(); if (!dr.read() dr["password"].tostring()!= txtpassword.text) MessageBox.Show("Invalid u/p"); else MessageBox.Show("Valid - UserId=" + dr["pkuserid"]); con.close(); Code: C# Login click event Private Sub btnlogin_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btnlogin.click Dim con As New SqlConnection(Helper.ConnectionString) Dim cmd As New SqlCommand() cmd.connection = con cmd.commandtext = "Select PKUserId, Password From UserProfile where Username='" + txtusername.text + "'" con.open() Dim dr As SqlDataReader = cmd.executereader() If ((dr.read()) OrElse (dr("password").tostring() <> txtpassword.text)) Then MessageBox.Show("Invalid u/p"); Else MessageBox.Show("Valid - UserId=" & dr("pkuserid")) End If con.close() End Sub Code: VB 13

14 MARS (Important for Interviews) By Default we can have only one data reader opened at a time on one connection object. If MultipleActiveResultSets=True is added to the connection string then more than one data reader can be opened at the same time on the single connection object. It s a feature in Ado.net 2.0 Department (DeptId, DeptName) Employee (EmpId, EmpName, EmpSalary, DeptId) Getting employees from a department Private Sub btngetdeptemp_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btngetdeptemp.click Dim con As New SqlConnection con.connectionstring = "Data Source=.\sqlexpress;Initial Catalog=MSNETDemoDb;Integrated Security=TRUE; MultipleActiveResultSets=True" Dim cmddept As New SqlCommand cmddept.commandtext = "Select * from Department" cmddept.commandtype = CommandType.Text cmddept.connection = con Dim drdept As SqlDataReader con.open() drdept = cmddept.executereader() Dim str As String = "" While (drdept.read()) Dim cmdemp As New SqlCommand cmdemp.commandtext = "Select * from Employee where Deptid=" & drdept("deptid") cmdemp.commandtype = CommandType.Text cmdemp.connection = con Dim dremp As SqlDataReader dremp = cmdemp.executereader()'this line fails if MARS is not mentioned in connection string. While (dremp.read()) str &= drdept("deptname") & vbtab str &= dremp("empid") & vbtab str &= dremp(1) & vbtab str &= dremp.getdecimal(2) & vbcrlf End While dremp.close() End While drdept.close() MsgBox(str) con.close() 14

15 End Sub Code: VB Getting employees from a department private void btngetallemps_click(object sender, EventArgs e) SqlConnection con = new SqlConnection(); con.connectionstring = "Data Source=.\\sqlexpress;Initial Catalog=MSNETDemoDb;Integrated Security=TRUE; MultipleActiveResultSets = true"; SqlCommand cmddept = new SqlCommand(); cmddept.commandtext = "Select * from Department"; cmddept.commandtype = CommandType.Text; cmddept.connection = con; SqlDataReader drdept; drdept = cmddept.executereader(); string str = ""; while (drdept.read()) SqlCommand cmdemp = new SqlCommand(); cmdemp.commandtext = ("Select * from Employee where Deptid=" + drdept["deptid"]); cmdemp.commandtype = CommandType.Text; cmdemp.connection = con; SqlDataReader dremp; //This line fails if MARS is not mentioned in connection string dremp = cmdemp.executereader(); while(dremp.read()) str += drdept["deptname"].tostring() + '\t'; str += dremp["empid"].tostring() + '\t'; str += dremp[1].tostring() + '\t'; str += dremp.getdecimal(2) + "\r\n"; dremp.close(); drdept.close(); MessageBox.Show(str); con.close(); Code: C# 15

16 Parameterized Prepared Statement Sql Statement on its first execution is compiled, optimized and an execution plan is created for it. If the statement is marked as prepared then for further usage this execution plan is cached by the backend, so that the same plan can be reused for the subsequent request for the same statement but different data. Note: The prepared statement must be framed using the parameters. But every parameterized statement need not be prepared. Program to display command line argument values Class Emp Public Name As String Public Salary As Decimal Public Sub New(ByVal name As String, ByVal salary As Decimal) Me.Name = name Me.Salary = salary End Sub End Class Code: VB Program to display command line argument values class Emp public string Name; public Decimal Salary; public Emp(string name, Decimal salary) this.name = name; this.salary = salary; Code: C# Procedure to execute a Prepared statement 1. Create a Connection object and set its ConnectionString Property 2. Create a Command object and set its Connection, CommandType and CommandText Properties. 3. The CommandText must include place holders for the parameters 4. For every placeholder in the statement, create a Parameter Object. 5. Add all the parameters to the Parameters collection of command object. 6. Open the Connection 7. Prepare the execution plan using Prepare() method of command object. 8. Set the values for parameters and Execute the Command 16

17 9. Repeat step 8 for different values of parameters 10. Close the connection. Program to Execute Insert Statement as Prepared statement Dim con As New SqlConnection(Helper.ConnectionString) Dim cmd As New SqlCommand cmd.connection = con cmd.commandtype = CommandType.Text cmd.commandtext = "Insert into Emp(EmpName, EmpSalary Values Dim parempname As SqlParameter parempname = New SqlParameter("@EmpName", SqlDbType.VarChar, 50) Dim parempsalary As SqlParameter parempsalary = cmd.createparameter() parempsalary.parametername = "@EmpSalary" parempsalary.sqldbtype = SqlDbType.Money cmd.parameters.add(parempname) cmd.parameters.add(parempsalary) Dim lstemps As New List(Of Emp) lstemps.add(new Emp("DE1", 10000)) lstemps.add(new Emp("DE2", 20000)) lstemps.add(new Emp("DE3", 30000)) lstemps.add(new Emp("DE4", 20000)) con.open() cmd.prepare() 'Prepares the execution plan For Each emp As Emp In lstemps parempname.value = emp.name parempsalary.value = emp.salary cmd.executenonquery() 'The prepared execution plan is used here Next con.close() Code: VB Program to Execute Insert Statement as Prepared statement SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand(); cmd.connection = con; cmd.commandtype = CommandType.Text; cmd.commandtext = "Insert into Emp(EmpName, EmpSalary Values SqlParameter parempname; parempname = new SqlParameter("@EmpName", SqlDbType.VarChar, 50); 17

18 SqlParameter parempsalary; parempsalary = cmd.createparameter(); parempsalary.parametername = "@EmpSalary"; parempsalary.sqldbtype = SqlDbType.Money; cmd.parameters.add(parempname); cmd.parameters.add(parempsalary); List lstemps = new List(Of, Emp); lstemps.add(new Emp("DE1", 10000)); lstemps.add(new Emp("DE2", 20000)); lstemps.add(new Emp("DE3", 30000)); lstemps.add(new Emp("DE4", 20000)); cmd.prepare(); // Prepares the execution plan foreach (Emp emp in lstemps) parempname.value = emp.name; parempsalary.value = emp.salary; cmd.executenonquery(); // The prepared execution plan is used here& con.close(); Code: C# 1. In Sql Server the parameters must begin In Oracle just the name is sufficient but for OleDb and Odbc Providers we need to use? as place holder for all the parameters and while adding the parameters a proper order must be maintained. 2. If the SQL Statement has to be executed only once, don t mark as Prepared because the backend takes extra time for preparation of execution plan and this would become overhead the plan is not reused. 3. If the parameter is of type varchar or string and if the value of it has single quote, don t replace that single quote with two single quotes (unlike in a simple statement with data directly embed into it). Inserting and reading Images: Create table TestBlob ( imphoto image not null ) Inserting Image into database: FileStream fs = new FileStream (textbox1.text, FileMode.Open, FileAccess.Read); byte[] rawbyte = new byte[fs.length]; 18

19 fs.read (rawbyte, 0, fs.rawbyte.length); con.open (); cmd = new SqlCommand ("Insert into TestBlob values(@photo)", con); SqlParameter par = cmd.parameters.addwithvalue ("@photo", SqlDbType.Image); par.value = rawbyte; cmd.executenonquery (); con.close (); Working with Stored Procedures A Stored Procedure is a set of SQL Statement together with some logic Pre-Compiled in native format and saved in the backend. Advantages: 1. They are faster in execution because they are precompiled and stored in backend in native form of that backend. 2. Reduces network traffic because they are executed in backend the data used by them is also in backend. 3. It s easy to update logic/code in them because it s stored only at one place i.e. in database. Sequence of Steps for Executing the Stored Procedure in front end application 1. Create a Connection object and set its ConnectionString Property 2. Create a Command object and set its Connection, CommandType and CommandText Properties. 3. For every parameter in the prepared statement / stored procedure, create a Parameter Object and set its ParameterName, Data Type, Size and Direction properties. 4. Add the Parameters to the Parameters collection of Command Object. 5. Set the value for all Input Parameters. 6. Open the Connection 7. Execute the Command using the appropriate Execute Method. 8. Close the Connection 9. Retrieve the value from output parameters. CREATE PROCEDURE GetSalary(@Id int,@sal money output ) AS Begin from Emp where EmpId=@Id End Note: In SQL Server every OUTPUT parameter is also treated as IN parameter. Example 1: Code to Execute a SP GetSalary Dim con As SqlConnection = New SqlConnection(Helper.ConnectionString) Dim cmd As SqlCommand = New SqlCommand("GetSalary", con) 'GetSalary is name of SP cmd.commandtype = CommandType.StoredProcedure 19

20 Dim parid As SqlParameter = cmd.parameters.add("@id", SqlDbType.Int) Dim parsalary As SqlParameter = cmd.parameters.add("@sal", SqlDbType.Money) parsalary.direction = ParameterDirection.Output parid.value = txtid.text con.open cmd.executenonquery con.close If (parsalary.value = DBNull.Value) Then txtsalary.text = "" Else txtsalary.text = parsalary.value.tostring End If Code: VB Example 1: Code to Execute a SP GetSalary SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand("GetSalary", con); //GetSalary is name of SP cmd.commandtype = CommandType.StoredProcedure; SqlParameter parid = cmd.parameters.add("@id", SqlDbType.Int); //Name and Type of Parameter must be same as in SP SqlParameter parsalary = cmd.parameters.add("@sal", SqlDbType.Money); parsalary.direction = ParameterDirection.Output; parid.value = txtid.text; cmd.executenonquery(); con.close(); if (parsalary.value == DBNull.Value) txtsalary.text = ""; else txtsalary.text = parsalary.value.tostring(); Code: C# CREATE PROCEDURE InsertEmp(@Id int money) AS Begin Insert into Emp(EmpName, EmpSalary) values (@Name,@Salary) End 2nd Example: To execute the Stored Procedure - InsertEmp 20

21 Dim con As SqlConnection = New SqlConnection(Helper.ConnectionString) Dim cmd As SqlCommand = New SqlCommand("InsertEmp", con) cmd.commandtype = CommandType.StoredProcedure Dim parsalary As SqlParameter parid = cmd.parameters.add("@id", SqlDbType.Int) parid.direction = ParameterDirection.Output parname = cmd.parameters.add("@name", SqlDbType.VarChar, 50) parsalary = cmd.parameters.add("@salary", SqlDbType.Money) parname.value = txtname.text parsalary.value = txtsalary.text con.open() cmd.executenonquery() con.close() txtid.text = parid.value.tostring Code: VB 2nd Example: To execute the Stored Procedure - InsertEmp SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand("InsertEmp", con); cmd.commandtype = CommandType.StoredProcedure; SqlParameter parid, parname, parsalary; parid = cmd.parameters.add("@id", SqlDbType.Int); parid.direction = ParameterDirection.Output; parname = cmd.parameters.add("@name", SqlDbType.VarChar, 50); parsalary = cmd.parameters.add("@salary", SqlDbType.Money); parname.value = txtname.text; parsalary.value = txtsalary.text; cmd.executenonquery(); con.close(); txtid.text = parid.value.tostring(); Code: C# Create Procedure GetEmployees AS Begin Select Count(*) from Emp Select EmpId, EmpName, EmpSalary from Emp End 3rd Example: Code to Execute the SP - GetEmployees 21

22 Dim con As New SqlConnection("Data Source=.\sqlexpress;Initial Catalog=MSDemoDb;Integrated Security=TRUE") Dim cmd As New SqlCommand cmd.commandtext = "GetEmployees" cmd.commandtype = CommandType.StoredProcedure cmd.connection = con con.open() Dim dr As SqlDataReader = cmd.executereader() dr.read() 'Moves to the only record in the first cursor created by execution of the stored procedure. MsgBox(dr(0)) 'Shows the total number of records in the Emp table.- i.e result of Select Count(*) from Emp dr.nextresult() 'Moves the Pointer to the second cursor. i.e Select EmpId, EmpName, EmpSalary from Emp Dim str As String = "" While (dr.read()) str &= dr("empid") & vbtab str &= dr(1) & vbtab Dim ind As Integer ind = dr.getordinal("empsalary") 'Return the Index of the column EmpSalary If (dr.isdbnull(ind)) Then str &= "--" & vbcrlf Else str &= dr.getdecimal(ind) & vbcrlf End If End While MsgBox(str) dr.close() con.close() Code: VB 3rd Example: Code to Execute the SP - GetEmployees SqlConnection con = new SqlConnection("Data Source=.\\sqlexpress;Initial Catalog=MSDemoDb;Integrated Security=TRUE"); SqlCommand cmd = new SqlCommand(); cmd.commandtext = "GetEmployees"; cmd.commandtype = CommandType.StoredProcedure; cmd.connection = con; SqlDataReader dr = cmd.executereader(); dr.read(); // Moves to the only record in the first cursor created by execution of the stored procedure. MessageBox.Show(dr[0].ToString()); 22

23 // Shows the total number of records in the Emp table.- i.e result of _Select Count(*) from Emp_ dr.nextresult(); string str = ""; while (dr.read()) str += dr["empid"].tostring() + '\t'; str += dr[1].tostring() + '\t'; int ind; ind = dr.getordinal("empsalary"); // Return the Index of the column EmpSalary if (dr.isdbnull(ind)) str += "--" + "\r\n"; else str += dr.getdecimal(ind) + "\r\n"; MessageBox.Show(str); dr.close(); con.close(); Code: C# Note: If required cmd.commandtext can have more than one sql statement separated by ;. This feature may not be supported by all databases. Working with Transactions Definition: It s a group of Sql Statements to be executed as one unit to modify the state of database. Backend is responsible for managing the transactions. To bind all the Command objects to a single Transaction do the following 1. On the Connection object begin the transaction (con.begintransaction), this returns the reference to the Transaction object (trans) encapsulating transaction created in the backend. 2. All the Command objects, Transaction Property must be set to the above Transaction object. 3. In Try block execute all the Commands 4. If the exception is not thrown the last statement of the try must Commit (trans.commit())the transaction, but if the exception is thrown the Catch must execute Rollback (trans.rollback()) on the transaction object. Step1: Create Account(AccountID, Balance) table in backend. Step2: Add constraint Balance >=

24 Step3: Write the following code in button click Transaction Example SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmdsource = new SqlCommand(); cmdsource.commandtext = "Update Account Set Balance = Balance - " + txtamount.text + " where AccountId=1"; cmdsource.connection = con; SqlCommand cmdtarget = new SqlCommand(); cmdtarget.commandtext = "Update Account Set Balance = Balance + " + txtamount.text + " where AccountId=2"; cmdtarget.connection = con; SqlTransaction trans = con.begintransaction(); cmdtarget.transaction = trans; cmdsource.transaction = trans; try cmdtarget.executenonquery(); cmdsource.executenonquery(); trans.commit(); catch (SqlException ex) trans.rollback(); MessageBox.Show(ex.Message); con.close(); Code: C# Note: Once a transaction has begun over a connection, a command without its transaction property set, cannot be executed on that connection unless either the transaction is committed or rolledback. Managing Transaction using TransactionScope 1. Add reference to System.Transactions 2. On top of file mention using System.Transactions (CS) or Imports System.Transactions (VB). 3. Enclose the block of code for execution of all commands in using block of TransactionScope object as below Transactions in ADO.net 2.0 using System.Transactions; SqlConnection con1 = new SqlConnection(Helper.ConnectionString); SqlConnection con2 = con1;// new SqlConnection(Helper.ConnectionString); SqlCommand cmdsource = new SqlCommand(); cmdsource.commandtext = "Update Account Set Balance = Balance - " + txtamount.text + " where AccountId=1"; cmdsource.connection = con1; SqlCommand cmdtarget = new SqlCommand(); 24

25 cmdtarget.commandtext = "Update Account Set Balance = Balance + " + txtamount.text + " where AccountId=2"; cmdtarget.connection = con2; using (TransactionScope ts = new TransactionScope()) con1.open(); // con2.open(); cmdtarget.executenonquery(); cmdsource.executenonquery(); con1.close(); //con2.close(); ts.complete(); Code: C# Advantage of using this over con.begintransaction: TransactionScope can encapsulate Distributed Transactions (while using more than one database) i.e. within TransactionScope all the commands executed fall under one transaction irrespective of their Connection (which can be same or different) Asynchronous Execution of SQL Commands BeginX / EndX Methods (Until Framework 4.0) OR XAsync Methods (from Framework 4.5) Step1: Create the Following Stored Procedure Create Procedure GetAllEmployees as Begin WAITFOR DELAY '00:00:10' --delay for 10secs Select * from Emp End Step2: Use any one of the following techniques: Async Execution using BeginX and EndX methods SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand("GetAllEmployees", con); cmd.commandtype = CommandType.StoredProcedure; IAsyncResult ar = cmd.beginexecutereader(); MessageBox.Show("Continue..."); while (!ar.iscompleted) Application.DoEvents(); SqlDataReader dr = cmd.endexecutereader(ar); 25

26 string str = ""; while (dr.read()) str += dr[0] + "\n"; dr.close(); con.close(); MessageBox.Show(str); Code: C# Async Execution using Async Methods and wait keyword private async void btnasyncusingasyncandwaitkeywords_click(object sender, EventArgs e) SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand("GetAllEmployees", con); cmd.commandtype = CommandType.StoredProcedure; SqlDataReader dr = await cmd.executereaderasync(); string str = ""; while (dr.read()) str += dr[0] + "\n"; con.close(); MessageBox.Show(str); Using Factory class for writing Provider Independent code How can we write code which is not directly using any provider specific classes and most of the things are done using interface? Namespace: System.Data.Common has the required Factory classes for doing the same. Program to display command line argument values Private Sub btnselectemployees_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btnselectemployees.click Dim fac As System.Data.Common.DbProviderFactory fac = System.Data.Common.DbProviderFactories.GetFactory("System.Data.SqlClient") Dim con As IDbConnection = fac.createconnection con.connectionstring = Helper.ConnectionString Dim cmd As IDbCommand = fac.createcommand cmd.commandtext = "Select * from Emp" cmd.connection = con con.open() Dim dr As IDataReader = cmd.executereader Dim str As String = "" 26

27 While dr.read Dim indempid As Integer = dr.getordinal("empid") str = (str _ + (dr.getint32(indempid) + "" & vbtab)) Dim indempname As Integer = dr.getordinal("empname") str = (str _ + (dr.getstring(indempname) + "" & vbtab)) Dim indempsalary As Integer = dr.getordinal("empsalary") If dr.isdbnull(indempsalary) Then str = (str + "" & vblf) Else str = (str _ + (dr.getdecimal(indempsalary) + "" & vblf)) End If End While dr.close() con.close() MessageBox.Show(str) End Sub Code: VB Program to display command line argument values private void btnselectemployees_click(object sender, EventArgs e) System.Data.Common.DbProviderFactory fac; fac = System.Data.Common.DbProviderFactories.GetFactory("System.Data.SqlClient"); IDbConnection con = fac.createconnection(); con.connectionstring = Helper.ConnectionString; IDbCommand cmd = fac.createcommand(); cmd.commandtext = "Select * from Emp"; cmd.connection = con; IDataReader dr = cmd.executereader(); string str = ""; while (dr.read()) int indempid = dr.getordinal("empid"); str += dr.getint32(indempid) + "\t"; int indempname = dr.getordinal("empname"); str += dr.getstring(indempname) + "\t"; 27

28 int indempsalary = dr.getordinal("empsalary"); if (dr.isdbnull(indempsalary)) str += "\n"; else str += dr.getdecimal(indempsalary) + "\n"; dr.close(); con.close(); MessageBox.Show(str); Code: C# How Generic code can be written Example for execution of Stored Procedure Program to show usage of Stored Procedure Class DBUtil Public Shared Function ExecuteSPNonQuery(ByVal spname As String, ByVal ParamArray params() As SqlParameter) As Integer Dim con As New SqlConnection(Helper.ConnectionString) Dim cmd As New SqlCommand(spName, con) cmd.commandtype = CommandType.StoredProcedure cmd.parameters.addrange(params) Try con.open() Return cmd.executenonquery() Finally con.close() End Try End Function Public Shared Function ExecuteSPDataReader(ByVal spname As String, ByVal ParamArray params() As SqlParameter) As SqlDataReader Dim con As New SqlConnection(Helper.ConnectionString) Dim cmd As New SqlCommand(spName, con) cmd.commandtype = CommandType.StoredProcedure For Each p As SqlParameter In params cmd.parameters.add(p) Next con.open() Return cmd.executereader(commandbehavior.closeconnection) Because CommandBehavior.CloseConnection is used as parameter for ExecureReader the 28

29 Connection will be automatically closed when the DataReader returned to the calling method is closed. End Function End Class Private Sub btnexecutesp_click(byval sender As System.Object, ByVal e As System.EventArgs) Handles btnexecutesp.click Dim cs As String = "server=.\sqlexpress;database=msnet;integrated security=true" Dim spname As String = "GetSalary" Dim pid As SqlParameter = New SqlParameter("@Id", SqlDbType.Int) pid.direction = ParameterDirection.Input Dim psalary As SqlParameter = New SqlParameter("@sal", SqlDbType.Money) psalary.direction = ParameterDirection.Output pid.value = CInt(txtId.Text) DBUtil.ExecuteSPNonQuery(cs, spname, pid, psalary) If (Not IsDBNull(pSalary.Value)) Then txtsalary.text = psalary.value End If End Sub Code: VB Program to show usage of Stored Procedure class DBUtil public static int ExecuteSPNonQuery(string spname, params SqlParameter[] params1) SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand(spName, con); cmd.commandtype = CommandType.StoredProcedure; cmd.parameters.addrange(params1); try return cmd.executenonquery(); finally con.close(); public static SqlDataReader ExecuteSPDataReader(string spname, params SqlParameter[] params1) 29

30 SqlConnection con = new SqlConnection(Helper.ConnectionString); SqlCommand cmd = new SqlCommand(spName, con); cmd.commandtype = CommandType.StoredProcedure; foreach (SqlParameter p in params1) cmd.parameters.add(p); return cmd.executereader(commandbehavior.closeconnection); private void btnexecutesp_click(object sender, System.EventArgs e) IDataReader reader; string cs = "server=.\\sqlexpress;database=msnet;integrated security=true"; string spname = "GetSalary"; SqlParameter pid = new SqlParameter("@Id", SqlDbType.Int); pid.direction = ParameterDirection.Input; SqlParameter psalary = new SqlParameter("@sal", SqlDbType.Money); psalary.direction = ParameterDirection.Output; pid.value = int.parse(txtid.text); DBUtil.ExecuteSPNonQuery(spName, pid, psalary); if (psalary.value!=null) txtsalary.text = psalary.value; Code: C# 30

31 Quick Overview of API Covered in this Chapter Important Members of SqlConnection: Properties: ConnectionString Methods: Open, Close, BeginTransaction Important Members of SqlCommand: Properties: Connection, CommandType, CommandText, Parameters Methods: ExecuteNonQuery, ExecuteScalar, ExecuteReader, CreateParameter, Prepare ExecuteNonQueryAsync, ExecuteScalarAsync, ExecuteReaderAsync BeginExecuteNonQuery, BegingExecuteReader EndExecuteNonQuery, EndExecuteReader Important Members of SqlDataReader: Properties: IndexProperty - [ ] Methods: Read, GetOrdinal, GetInt32, GetString..GetX (X is datatype), IsDbNull,Close, HasRows Important Members of SqlParameter: Properties: Value, ParameterName, SqlDbType, Size, Direction Methods: Important Members of SqlTransaction: Properties: Methods: Commit, Rollback TransactionScope: Complete() Summary: In this section we have studied ADO.NET managed providers, writing a sample application to test connection, different ways of SQL Command Execution methods, Multiple Active Record Sets, using prepared statement, Stored Procedures, Transaction and Factory class. 31