OLEDB Connection string

The C# OleDbConnection instance takes Connection String as argument and pass the value to the Constructor statement. An instance of the C# OleDbConnection class is supported the OLEDB Data Provider .

 connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;
  Data Source=yourdatabasename.mdb;";
      

        cnn = new OleDbConnection(connetionString);

When the connection is established between C# application and the specified Data Source, SQL Commands will execute with the help of the Connection Object and retrieve or manipulate data in the database. Once the Database activities is over Connection should be closed and release from the data source resources .

 

  cnn.Close();

The Close() method in the OleDbConnection class is used to close the Database Connection. The Close method Rolls Back any pending transactions and releases the Connection from the Database connected by the OLEDB Data Provider.

 

 

using System;
using System.Windows.Forms;
using System.Data.OleDb; 

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            OleDbConnection cnn ;
            connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=yourdatabasename.mdb;";
            cnn = new OleDbConnection(connetionString);
            try
            {
                cnn.Open();
                MessageBox.Show ("Connection Open ! ");
                cnn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Can not open connection ! ");
            }
        }
    }
}

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C# ADO.NET SqlCommand - ExecuteScalar

The ExecuteScalar() in C# SqlCommand Object is using for retrieve a single value from Database after the execution of the SQL Statement. The ExecuteScalar() executes SQL statements as well as Stored Procedure and returned a scalar value on first column of first row in the returned Result Set.

 Command.ExecuteScalar();

The ExecuteNonQuery() performs Data Definition tasks as well as Data Manipulation tasks also. The Data Definition tasks like creating Stored Procedures ,Views etc. perform by the ExecuteNonQuery() . Also Data Manipulation tasks like Insert , Update , Delete etc. also perform by the ExecuteNonQuery() of SqlCommand Object.

If the Result Set contains more than one columns or rows , it will take only the value of first column of the first row, and all other values will ignore. If the Result Set is empty it will return a NULL reference.

It is very useful to use with aggregate functions like Count(*) or Sum() etc. When compare to ExecuteReader() , ExecuteScalar() uses fewer System resources.

The following C# example shows how to use the method ExecuteScalar() through SqlCommand Object.

using System;
using System.Windows.Forms;
using System.Data.SqlClient; 

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            SqlConnection cnn ;
            SqlCommand cmd ;
            string sql = null;

            connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
            sql = "Your SQL Statement Here like Select Count(*) from product";

            cnn = new SqlConnection(connetionString);
            try
            {
                cnn.Open();
                cmd = new SqlCommand(sql, cnn);
                Int32 count = Convert.ToInt32(cmd.ExecuteScalar());
                cmd.Dispose();
                cnn.Close();
                MessageBox.Show (" No. of Rows " + count);
            }
            catch (Exception ex)
            {
                MessageBox.Show("Can not open connection ! ");
            }
        }
    }
}

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C# ADO.NET SqlCommand - ExecuteNonQuery

The ExecuteNonQuery() is one of the most frequently used method in SqlCommand Object, and is used for executing statements that do not return result sets (ie. statements like insert data , update data etc.) .

 Command.ExecuteNonQuery();

The ExecuteNonQuery() performs Data Definition tasks as well as Data Manipulation tasks also. The Data Definition tasks like creating Stored Procedures ,Views etc. perform by the ExecuteNonQuery() . Also Data Manipulation tasks like Insert , Update , Delete etc. also perform by the ExecuteNonQuery() of SqlCommand Object.

The following C# example shows how to use the method ExecuteNonQuery() through SqlCommand Object.

using System;
using System.Windows.Forms;
using System.Data.SqlClient; 

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            SqlConnection cnn ;
            SqlCommand cmd ;
            string sql = null;

            connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
            sql = "Your SQL Statemnt Here";

            cnn = new SqlConnection(connetionString);
            try
            {
                cnn.Open();
                cmd = new SqlCommand(sql, cnn);
                cmd.ExecuteNonQuery();
                cmd.Dispose();
                cnn.Close();
                MessageBox.Show (" ExecuteNonQuery in SqlCommand executed !!");
            }
            catch (Exception ex)
            {
                MessageBox.Show("Can not open connection ! ");
            }
        }
    }
}

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C# ADO.NET SqlDataReader

SqlDataReader Object provides a connection oriented data access to the SQL Server data Sources from C# applications. ExecuteReader() in the SqlCommand Object sends the SQL statements to the SqlConnection Object and populate a SqlDataReader Object based on the SQL statement or Stored Procedures.

 
SqlDataReader sqlReader = sqlCmd.ExecuteReader();
  

When the ExecuteReader method in the SqlCommand Object execute , it will instantiate a SqlClient.SqlDataReader Object. When we started to read from a DataReader it should always be open and positioned prior to the first record. The Read() method in the DataReader is used to read the rows from DataReader and it always moves forward to a new valid row, if any row exist .

 
SqlDataReader.Read();
  

using System;
using System.Windows.Forms;
using System.Data.SqlClient; 

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            SqlConnection sqlCnn ;
            SqlCommand sqlCmd ;
            string sql = null;

            connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
            sql = "Your SQL Statement Here , like Select * from product";

            sqlCnn = new SqlConnection(connetionString);
            try
            {
                sqlCnn.Open();
                sqlCmd = new SqlCommand(sql, sqlCnn);
                SqlDataReader sqlReader = sqlCmd.ExecuteReader();
                while (sqlReader.Read())
                {
                    MessageBox.Show(sqlReader.GetValue(0) + " - " + sqlReader.GetValue(1) + " - " + sqlReader.GetValue(2));
                }
                sqlReader.Close();
                sqlCmd.Dispose();
                sqlCnn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Can not open connection ! ");
            }
        }
    }
}

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C# ADO.NET SqlDataAdapter

SqlDataAdapter Class is a part of the C# ADO.NET Data Provider and it resides in the System.Data.SqlClient namespace. SqlDataAdapter provides the communication between the Dataset and the SQL database. We can use SqlDataAdapter Object in combination with Dataset Object. DataAdapter provides this combination by mapping Fill method, which changes the data in the DataSet to match the data in the data source, and Update, which changes the data in the data source to match the data in the DataSet.

 
 SqlDataAdapter adapter = new SqlDataAdapter();

  adapter.Fill(ds);
  

The SqlDataAdapter Object and DataSet objects are combine to perform both data access and data manipulation operations in the SQL Server Database. When the user perform the SQL operations like Select , Insert etc. in the data containing in the Dataset Object , it won't directly affect the Database, until the user invoke the Update method in the SqlDataAdapter.

using System;
using System.Windows.Forms;
using System.Data;
using System.Data.SqlClient; 

namespace WindowsApplication1
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string connetionString = null;
            SqlConnection sqlCnn ;
            SqlCommand sqlCmd ;
            SqlDataAdapter adapter = new SqlDataAdapter();
            DataSet ds = new DataSet();
            int i = 0;
            string sql = null;

            connetionString = "Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password";
            sql = "Select * from product";

            sqlCnn = new SqlConnection(connetionString);
            try
            {
                sqlCnn.Open();
                sqlCmd = new SqlCommand(sql, sqlCnn);
                adapter.SelectCommand = sqlCmd;
                adapter.Fill(ds);
                for (i = 0; i <= ds.Tables[0].Rows.Count - 1; i++)
                {
                    MessageBox.Show(ds.Tables[0].Rows[i].ItemArray[0] + " -- " + ds.Tables[0].Rows[i].ItemArray[1]);
                }
                adapter.Dispose();
                sqlCmd.Dispose();
                sqlCnn.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show("Can not open connection ! ");
            }
        }
    }
}

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get the sql server version

 We can get the sql server version by using this query :

DECLARE @ver nvarchar(128);
SET @ver = CAST(serverproperty('ProductVersion') AS nvarchar);
SET @ver = SUBSTRING(@ver, 1, CHARINDEX('.', @ver) - 1)

IF ( @ver = '7' )
   SELECT 'SQL Server 7'
ELSE IF ( @ver = '8' )
   SELECT 'SQL Server 2000'
ELSE IF ( @ver = '9' )
   SELECT 'SQL Server 2005'
ELSE IF ( @ver = '10' )
   SELECT 'SQL Server 2008/2008 R2'
ELSE IF ( @ver = '11' )
   SELECT 'SQL Server 2012'
ELSE
SELECT 'Unsupported SQL Server Version'
  

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