c# - ASP.Net form throwing SQL exception -

when trying save , store data in local sql database, sql exception thrown,

"a network-related or instance-specific error occurred while establishing connection sql server. server not found or not accessible. verify instance name correct , sql server configured allow remote connections. (provider: named pipes provider, error: 40 - not open connection sql server)"

initially thought wrong way had made new data connection. after making new table 3 times, problem persisted. tried re-install sql modules of visual studio, did not yield +ve result.

no data can read from/stored table. please help.

public partial class signup : system.web.ui.page {     sqlconnection conn = new sqlconnection("data source=(localdb)\v11.0;initial catalog=kidzquiz;integrated security=true");     sqlcommand cmd;     sqldataadapter da;     dataset ds;   protected void signupclick(object s, eventargs e) {     //if (checkduplicate() != 0)         //signup_error.text = "user exists";     //else if (checkempty() != 1)        // signup_error.text = "one or more fields missing";     //else     //{         string sqlcmd = "insert user (name, email, school, city, standard, section) values (@n, @em, @sc, @city, @st, @sec)";         cmd = new sqlcommand(sqlcmd, conn);         cmd.parameters.addwithvalue("@n", name.text);         cmd.parameters.addwithvalue("@em", email_signup.text);         cmd.parameters.addwithvalue("@sc", school.text);         cmd.parameters.addwithvalue("@city", city.text);         cmd.parameters.addwithvalue("@st", standard.selecteditem.tostring());         cmd.parameters.addwithvalue("@sec", section.selecteditem.tostring());         conn.open();         cmd.executenonquery();         conn.close();     //} } 

}

in localdb local databases have give path database file also.

data source=(localdb)\v11.0;attachdbfilename=|datadirectory|\db.mdf;integrated security=true 

|datadirectory| represents app_data folder of application