Set Your Connection String As...
<connectionStrings>
<add name="ConnectionString" connectionString="Data Source=OmPatel\SQLEXPRESS;Initial Catalog=GOLDLOAN;Integrated Security=True"
providerName="System.Data.SqlClient" />
</connectionStrings>
<system.web>
And Retrive In Code Behind As
..
string strConnString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
SqlConnection con = new SqlConnection(strConnString);
con.Open();