It is also a special type of configuration which is use in window service, window application, console application and WPF application. This configuration set all setting of this type of application in .net programming. It parse at compile time means that if you edit the configuration file at running time then you need to restart the application for reload the settings.

In this configuration store many types of setting.

• Database setting

• Connection string

• Error handling

• Managing the log files

• Security

• External file configuration

Example

<?xml version='1.0' encoding='utf-8' ?>

<configuration>

    <startup>

        <supportedRuntime version='v4.0' sku='.NETFramework,Version=v4.5' />

    </startup>

</configuration>

Or

<?xml version='1.0'?>

<configuration>

 <connectionStrings>

  <add name='MyKey'

 connectionString='Data Source=localhost;Initial Catalog=ABC;'

 providerName='System.Data.SqlClient'/>

     </connectionStrings>

</configuration>

 It is a special type of configuration file this file is create in operating system. This store the machine configuration. Like device name, version, and only one machine file build in the system and store high level of system configuration.

 The connection string use in .net programming for connecting to .net application with database. This connection string passes in web.config and app.config file using the connectionstring tag in config file. This connection string tag take ADD tag for adding the attribute in connection string. We can add more than on connection string, the application use this string at runtime for fetching database value for database.

In ADD tag have attributes for adding the connection details

• Name

• Connection string

• Provider name

In the connection string attribute we can give

• Server

• Database name

• Initial catalog

• Connection User id

• Connection Password

• Connection Time out

• Integrated security

• Connection pool size

• Encryption

<?xml version='1.0' encoding='utf-8'?>

<configuration>

  <connectionStrings>

     <add name='myConnection' connectionString='server=localhost;database=mydatabase;' />

  </connectionStrings>

</configuration>

Fetching the connection string is done using the ConfigurationManager in class program.

string conn = ConfigurationManager.ConnectionStrings['myConnection'].ConnectionString;

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 ;

   connetionString = 'Data Source=ServerName;Initial Catalog=DatabaseName;User ID=UserName;Password=Password'

            cnn = new SqlConnection(connetionString);

            try

            {

                cnn.Open();

                MessageBox.Show ('Connection Open ! ');

                cnn.Close();

            }

            catch (Exception ex)

            {

                MessageBox.Show('Can not open connection ! ');

            }

        }

    }

}

<connectionStrings>

  <add

    name='sqlServer'

    providerName='System.Data.SqlClient'

    connectionString='Data Source=localhost;Initial Catalog=MyDatabase;Integrated Security=True;' />

</connectionStrings>

<connectionStrings>

  <add

    name='sqlServer'

    providerName='System.Data.SqlClient'

    connectionString='Data Source=localhost;Initial Catalog=MyDatabase;Integrated Security=True;Connection Timeout=60' />

</connectionStrings>

<connectionStrings>

  <add

    name='sqlServer'

    providerName='System.Data.SqlClient'

    connectionString='Data Source=localhost;Initial Catalog=MyDatabase;User Id=user;Password=pwd;' />

</connectionStrings>

<connectionStrings>

  <add

    name='mySql'

    providerName='MySql.Data.MySqlClient'

    connectionString='Server=localhost;Database=MyDatabase;Uid=user;Pwd=pwd;' />

</connectionStrings>

<connectionStrings>

  <add

    name='mySql'

    providerName='MySql.Data.MySqlClient'

    connectionString='Server=localhost;Database=MyDatabase;IntegratedSecurity=yes;Uid=auth_windows;' />

</connectionStrings>

<connectionStrings>

  <add

    name='mySql'

    providerName='MySql.Data.MySqlClient'

    connectionString='...;MinimumPoolSize=10;maximumpoolsize=50;' />

</connectionStrings>