Read or Write connection strings in web.config file using asp.net

open web.config file in application and add sample db connection in connectionStrings section like this 

<connectionStrings> <add name="yourconnectinstringName" connectionString="Data Source= DatabaseServerName; Integrated Security=true;Initial Catalog= YourDatabaseName; uid=YourUserName; Password=yourpassword; " providerName="System.Data.SqlClient"/> </connectionStrings >

Example of declaring connectionStrings in web.config file like this

<connectionStrings> <add name="dbconnection" connectionString="Data Source=SureshDasari;Integrated Security=true;Initial Catalog=MySampleDB" providerName="System.Data.SqlClient"/> </connectionStrings >

After add dbconnection in connectionString we need to write the some code in our codebehind file to get connection string from web.config file for that add following namespace in codebehind file and write the following code

using System.Configuration;

 This namespace is used to get configuration section details from web.config file.

After add namespaces write the following code in code behind

C# code

using System; using System.Data.SqlClient; using System.Configuration; public partial class _Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) {    //Get connection string from web.config file string strcon = ConfigurationManager.ConnectionStrings["dbconnection"].ConnectionString; //create new sqlconnection and connection to database by using connection string from web.config file SqlConnection con = new SqlConnection(strcon); con.Open(); } }

VB.NET

Imports System.Data.SqlClient Imports System.Configuration Partial Public Class _Default Inherits System.Web.UI.Page Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) 'Get connection string from web.config file Dim strcon As String = ConfigurationManager.ConnectionStrings("dbconnection").ConnectionString 'create new sqlconnection and connection to database by using connection string from web.config file Dim con As New SqlConnection(strcon) con.Open() End Sub End Class