Introduction
When your application connects to a database or
a data file you let ADO or ADO.Net utilize a provider to do the job for you. The
connection string contains the information that the provider need to know to be
able to establish a connection to the database or the data file. Because there
are different providers and each providers have multiple ways to make a
connection there are many different ways to write a connection string. The
connection string is really just a string inside your application. A connection
string contains initialization information that is passed as a parameter from a
data provider to a data source. The syntax depends on the data provider and the
connection string is parsed during the attempt to open a connection. Syntax
errors generate a run-time exception but other errors occur only after the data
source receives connection information. Connection strings are used when the
SQLDriverConnect and SQLBrowseConnect ODBC API functions are called. They may
specify as little as a data source name or as much as an entire data source
configuration. The SQLDriverConnect function will interactively complete a
connection string, if necessary and if the calling program indicates that it
wants this behavior by prompting the user for the missing information.
In ADO.NET you create and manage connections
using connection objects
- SqlConnection : An object that
manages a connection to a SQL Server version 7.0 or later. It is optimized
for use with SQL Server 7.0 or later by bypassing the OLE DB layer.
- OleDbConnection : An object
that manages a connection to any data store accessible via OLE DB.
- OdbcConnection : An object that
manages a connection to a data source created by using a connection string
or ODBC data source name (DSN).
- OracleConnection : An object that
manages a connection to Oracle databases.
Example : Simple example of a connection
string in ADO.NET.
Code
using System;
using
System.Data;
using
System.Data.SqlClient;
class
Program
{
static void
Main()
{
string connectionString =
"Data Source=(local);Initial Catalog=manish;"
+ "Integrated Security=true";
string queryString =
"SELECT ProductID, UnitPrice,
ProductName from dbo.products "
+ "WHERE UnitPrice > @pricePoint
"
+ "ORDER BY UnitPrice DESC;";
int paramValue = 5;
using (SqlConnection connection =
new SqlConnection(connectionString))
{
SqlCommand command = new
SqlCommand(queryString, connection);
command.Parameters.AddWithValue("@pricePoint",
paramValue);
try
{
connection.Open();
SqlDataReader reader = command.ExecuteReader();
while (reader.Read())
{
Console.WriteLine("\t{0}\t{1}\t{2}",
reader[0], reader[1], reader[2]);
}
reader.Close();
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
Console.ReadLine();
}
}
}