ASP.NET Read Database Connection Strings from the Web.config File

This example reads a connection string from a Web.config file.

Add Below Code lines in Web.Config File under <configuration> tag

<appSettings>

    <add key="conn" value="Data Source=WIN-OOYB15IDNT4\MSSQLSERVER1;Initial Catalog=infodb; user id=sa;password=password@789"/>

</appSettings>

Code Behind to Access Connection string C#:

Add two namespace in Code behind:

using System.Data.SqlClient;

using System.Configuration;

Code in Page Load event: 

protected void Page_Load(object sender, EventArgs e)

{

   try

   {

       SqlConnection conn = new SqlConnection(ConfigurationManager.AppSettings["conn"]);

       conn.Open();

       //your ADO.NET code goes here

       Response.Write("Connection Opened Successfully...!!!");

       conn.Close();

    }

    catch (Exception ex)

    {

            Response.Write(ex.ToString());

    }

 } 

Reference: http://msdn.microsoft.com/en-us/library/ms178411%28v=vs.100%29.aspx