Onion Architecture Unit Of Work Transaction Not getting Connection String - asp.net

Question

I am using Onion Architecture with Autofac. In my Dependency Injection Code, I am using:
[assembly: WebActivatorEx.PostApplicationStartMethod(typeof(IocConfig), "RegisterDependencies")]
namespace AppMVC.Infrastructure.Bootstrapper
{
public class IocConfig
{
public static void RegisterDependencies()
{
var builder = new ContainerBuilder();
builder.RegisterType(typeof(UnitOfWork)).As(typeof(IUnitOfWork)).InstancePerHttpRequest();
builder.Register<IEntitiesContext>(b =>
{
var context = new MyContext("My Connection String");
return context;
}).InstancePerHttpRequest();
}
}
}
Unit Of Work Code:
public class UnitOfWork : IUnitOfWork
{
private readonly IEntitiesContext _context;
private bool _disposed;
private Hashtable _repositories;
public UnitOfWork(IEntitiesContext context)
{
_context = context;
}
public int SaveChanges()
{
return _context.SaveChanges();
}
public IRepository<TEntity> Repository<TEntity>() where TEntity : BaseEntity
{
if (_repositories == null)
{
_repositories = new Hashtable();
}
var type = typeof(TEntity).Name;
if (_repositories.ContainsKey(type))
{
return (IRepository<TEntity>)_repositories[type];
}
var repositoryType = typeof(EntityRepository<>);
_repositories.Add(type, Activator.CreateInstance(repositoryType.MakeGenericType(typeof(TEntity)), _context));
return (IRepository<TEntity>)_repositories[type];
}
public void BeginTransaction()
{
_context.BeginTransaction();
}
public int Commit()
{
return _context.Commit();
}
public void Rollback()
{
_context.Rollback();
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
public virtual void Dispose(bool disposing)
{
if (!_disposed && disposing)
{
_context.Dispose();
foreach (IDisposable repository in _repositories.Values)
{
repository.Dispose();// dispose all repositries
}
}
_disposed = true;
}
}
MyContext Code:
public class MyContext : DbContext, IEntitiesContext
{
private ObjectContext _objectContext;
private DbTransaction _transaction;
public MyContext(string nameOrConnectionString)
: base(nameOrConnectionString)
{
}
public void BeginTransaction()
{
_objectContext = ((IObjectContextAdapter)this).ObjectContext;
if (_objectContext.Connection.State == ConnectionState.Open)
{
if (_transaction == null)
{
_transaction = _objectContext.Connection.BeginTransaction();
}
return;
}
_objectContext.Connection.Open(); // At this Line, I am getting Exception
if (_transaction == null)
{
_transaction = _objectContext.Connection.BeginTransaction();
}
}
public int Commit()
{
var saveChanges = SaveChanges();
_transaction.Commit();
return saveChanges;
}
public void Rollback()
{
_transaction.Rollback();
}
}
My problem is, On _objectContext.Connection.Open();, I am getting Connection String missing error.
Below is the screenshot of the Exception: