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