i have connection string stored in web.config file but it is giving me the error.
<connectionStrings>
<add name="ConnectionString" connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\DbProduct.mdf;Integrated Security=True;User Instance=True"
providerName="System.Data.SqlClient" />
where is the bug in the connection string. i have stored my db DbProduct.mdf in app_data folder. i have never use SQLEXPRESS. so i need guide line. thanks