<add name="LH_RPMDB"
     connectionString="data source=localhostdb;Database=dbsim;user id=sim;password=sim;Application Name=SIM-LH;"
     providerName="System.Data.SqlClient" />
<add name="DEV_RPMDB"
     connectionString="data source=devdb;Database=dbsim;user id=sim;password=sim;Application Name=SIM-dev;"
     providerName="System.Data.SqlClient" />
<add name="QA_RPMDB"
     connectionString="data source=qadb;Database=dbsim;user id=sim;password=sim;Application Name=SIM-qa;"
     providerName="System.Data.SqlClient" />

public class RPMContext : DbContext

ws.Url = ConfigurationSettings.AppSettings(ConfigurationSettings.AppSettings("Environment") + "_SNTRAX")

<connectionStrings>
    <add name="DefaultConnection"
         connectionString ...

public TrackerContext() : base("Name=DefaultConnection") {}

public partial class HOLDbEntities
{
    public HOLDbEntities(string connectionString)
        : base(connectionString)