EF6 Database First (DbContext) - Change Schema at runtime

Problem:
There are two SQL databases (dev and live) with on Azure
which has identical table structures but different table schema name. We
need a way to change the schema name at runtime thus we can maintain
one code base for the two database

Solution:

public class DBHelper
{
public static MyDBEntities Connect()
{
if (ConfigurationManager.ConnectionStrings["DBConnection"] == null)
{
throw new ApplicationException("connectionStrings in .config file is missing a connection named 'connectionStrings'");
}
string connectionString = ConfigurationManager.ConnectionStrings["DBConnection"].ConnectionString;

//parse schema name from database name
SqlConnection conn = new SqlConnection(connectionString);
string schema = conn.Database.Replace("_db", "");
return Connect<MyDBEntities>(connectionString, schema);
}
private static T Connect<T>(string connectionString, string schema) where T : DbContext
{
var assembly = typeof(T).Assembly;

var type = typeof(T);
var resourceNames = assembly.GetManifestResourceNames();
string contextName = null;

// code used to avoid of getting the wrong csdl, used when you have more than one
// DbContext on your project
foreach (var csdl in resourceNames.Where(r => r.EndsWith(".csdl")))
{
var csdlDocument = XDocument.Load(assembly.GetManifestResourceStream(csdl));
XNamespace csdlNamespace = "http://schemas.microsoft.com/ado/2009/11/edm";
var name = csdlDocument.Root.Elements(csdlNamespace + "EntityContainer").First().Attribute("Name").Value;

if (type.Name.Equals(name))
{
contextName = csdl.Replace(".csdl", "");
break;
}
}

string csdlName = resourceNames.Single(r => r.Equals(contextName + ".csdl"));
string ssdlName = resourceNames.Single(r => r.Equals(contextName + ".ssdl"));
string mslName = resourceNames.Single(r => r.Equals(contextName + ".msl"));

var ssdlDocument = XDocument.Load(assembly.GetManifestResourceStream(ssdlName));
XNamespace ssdlNamespace = "http://schemas.microsoft.com/ado/2009/11/edm/ssdl";
var functions = ssdlDocument.Root.Elements(ssdlNamespace + "Function").ToList();

foreach (var f in functions)
f.SetAttributeValue("Schema", schema);

var entitySets = ssdlDocument.Root.Elements(ssdlNamespace + "EntityContainer").ToList().Elements(ssdlNamespace + "EntitySet").ToList();

foreach (var es in entitySets)
if (es.Attribute("Schema") != null) es.SetAttributeValue("Schema", schema);

Func<string, XmlReader[]> getFromResource = (name) =>
{
using (var s = assembly.GetManifestResourceStream(name))
{
return new XmlReader[] { XDocument.Load(s).CreateReader() };
}
};

var storeItems = new StoreItemCollection(new XmlReader[] { ssdlDocument.CreateReader() });
var edmItems = new EdmItemCollection(getFromResource(csdlName));
var mappingItems = new StorageMappingItemCollection(edmItems, storeItems, getFromResource(mslName));

var workspace = new MetadataWorkspace();
workspace.RegisterItemCollection(storeItems);
workspace.RegisterItemCollection(edmItems);
workspace.RegisterItemCollection(mappingItems);
workspace.RegisterItemCollection(new ObjectItemCollection());
workspace.LoadFromAssembly(assembly);

var storeConn = new SqlConnection(connectionString);

ConstructorInfo contextConstructor = typeof(T).GetConstructor(new Type[] { typeof(DbConnection)}); //require a partial class of the EF model to accept one parameter of type DbConnection
var entityConn = new EntityConnection(workspace, storeConn);
return (T)contextConstructor.Invoke(new Object[] { entityConn });
}
}

public partial class MyDBEntities
{
public MyDBEntities(DbConnection existingConnection):base(existingConnection,true)
{
}
}

then can use the entity like below with the DBHelper

using (var db = DBHelper.Connect())
{
//you code here to use db
}

Note: if you use different EF version, you may need to change the csdl or ssdl namespace in above code
Reference:
http://blogs.msdn.com/b/dbrowne/archive/2013/08/30/entity-framework-schema-redirection.aspx http://pastebin.com/UpqUzezq