I get error when I use myConnection insted of DefaultConnection

<div class="userinput"> I can't understand this if I use name = DefaultConnection as in this example here it works
 <connectionStrings>       <add name="DefaultConnection" connectionString="Data Source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\WebFormsIdentity.mdf;Initial Catalog=WebFormsIdentity;Integrated Security=True"             providerName="System.Data.SqlClient" />   </connectionStrings>
but if I instead change name from DefaultConnection to MyConnection as in this example
 <connectionStrings>       <add name="MyConnection" connectionString="Data Source=(LocalDb)\v11.0;AttachDbFilename=|DataDirectory|\WebFormsIdentity. ...