How to split a connection string between multiple data objects

Assume first that DbContext and model / database.

• Leave the generated EF connection strings in the app.config file intact. As Arthur said, they contain paths to EF metadata (csdl / ssdl / msl). They are also used during development by a fashion designer.
• , , "SharedConnection". , .
• , DbContext .
• EF- . , :

public class BaseContext : DbContext
{
    public BaseContext(string nameOrConnectionString)
        : base(CreateConnection(nameOrConnectionString), true)
    {
    }

    private static EntityConnection CreateConnection(string connectionString)
    {
        // Create a (plain old database) connection using the shared connection string.
        DbConnection dbConn = Database.DefaultConnectionFactory.CreateConnection(
            ConfigurationManager.ConnectionStrings["SharedConnection"].ConnectionString);

        // Create a helper EntityConnection object to build a MetadataWorkspace out of the
        // csdl/ssdl/msl parts of the generated EF connection string for this DbContext.
        EntityConnection wsBuilder = new EntityConnection(connectionString);

        // Merge the specific MetadataWorkspace and the shared DbConnection into a new EntityConnection.
        return new EntityConnection(wsBuilder.GetMetadataWorkspace(), dbConn);
    }
}

, , BaseContext. CreateConnection. .

private static EntityConnection CreateConnection(string connectionString)
{
    // Find the name of the shared connection string.
    const string appSettingKey = "SharedConnectionStringName";

    string sharedConnectionStringName = ConfigurationManager.AppSettings[appSettingKey];
    if (string.IsNullOrEmpty(sharedConnectionStringName))
    {
        throw new Exception(string.Format(
            "Shared connection not configured. " +
            "Please add a setting called \"{0}\" to the \"appSettings\" " +
            "section of the configuration file.", appSettingKey));
    }

    // Create a (plain old database) connection using the shared connection string.
    ConnectionStringSettings backendSettings =
        ConfigurationManager.ConnectionStrings[sharedConnectionStringName];
    if (backendSettings == null)
    {
        throw new Exception(string.Format(
            "Invalid connection string name \"{0}\" in appSetting \"{1}\"",
            sharedConnectionStringName, appSettingKey));
    }

    System.Data.Common.DbConnection dbConn =
        Database.DefaultConnectionFactory.CreateConnection(
        backendSettings.ConnectionString);

    // Create a helper EntityConnection object to build a MetadataWorkspace out of the
    // csdl/ssdl/msl parts of the generated EF connection string for this DbContext.
    EntityConnection wsBuilder = new EntityConnection(connectionString);

    // Merge the specific MetadataWorkspace and the shared DbConnection into a new EntityConnection.
    return new EntityConnection(wsBuilder.GetMetadataWorkspace(), dbConn);
}