Global variables can use in dbcontext scope

Solution 1: Dependency Injection

This solution is pretty extensible, but you would have to modify the code in your repositories and controllers to use the injected dependencies instead of creating new instances with new.

1. Install Ninject. In Visual Studio, find the Package Manager Console and run Install-Package Ninject.MVC4 -dependencyVersion Highest in there.

2. Add constructor injection. Modify your controller, so that it gets an instance of your repository in its constructor. Modify your repository, so that it gets an instance of your entity context in its constructor. Cache your dependencies in private fields. Example code:

   // In your controller:
   public MyController(MyRepository repo)
   {
       this.repo = repo;
   }
   
   // In your repository:
   public MyRepository(Entities context)
   {
       this.context = context;
   }
   
   // In your entities:
   public Entities(UserInfo userInfo)
   {
       this.userInfo = userInfo;
   }
   

3. Add a UserInfo provider. We need to tell Ninject where to get the UserInfo from. We can use the provider interface here:

   public class UserInfoProvider : Provider<UserInfo>
   {
       protected override UserInfo CreateInstance(IContext context)
       {
           UserInfo UserInfo = new UserInfo();
   
           // Do some complex initialization here.
   
           return userInfo;
       }
   }
   

4. Add bindings. We need to tell Ninject to use the provider. We also want the lifetime of a UserInfo instance and of our entity context to be bound to the request cycle of MVC. Update your App_Start\NinjectWebCommon.cs:

   private static void RegisterServices(IKernel kernel)
   { 
       kernel.Bind<Entities>()
             .ToSelf()
             .InRequestScope();
   
       kernel.Bind<UserInfo>()
             .ToProvider<UserInfoProvider>()
             .InRequestScope();
   }
   

5. Run your app. Ninject should use your constructors and provide the requested dependencies.

For further information, visit the Ninject Wiki.

Solution 2: Thread local context

This requires no modification to your repositories, but it makes the code less testable and resembles an anti pattern somehow. This won't work if your controller calls multithreaded code.

1. Add context class.

   public class UserInfoContext : IDisposable
   {
       private static readonly ThreadLocal<UserInfo> UserInfos = new ThreadLocal<UserInfo>();
   
       public static UserInfo Current
       {
           get 
           {
               if (UserInfos == null)
               {
                   throw new InvalidOperationException("UserInfoContext has not been set.");
               }
   
               return UserInfos.Value;
           }
       }
   
       public static UserInfoContext Create(UserInfo userInfo)
       {
           if (userInfo == null)
           {
               throw new ArgumentNullException("userInfo");
           }
   
           if (UserInfos.Value != null)
           {
               throw new InvalidOperationException("UserInfoContext should not be nested.");
           }
   
           UserInfos.Value = userInfo;
   
           return new UserInfoContext();
       }
   
       private UserInfoContext() { }
   
       public void Dispose()
       {
           UserInfos.Value = null;
       }
   }
   

2. Wrap your controller code. Example:

   public ActionResult Index()
   {
       using (UserInfoContext.Create(myUserInfo))
       {
           // do stuff that calls your repositories
   
           return View();
       }
   }
   

3. Update your Entities class.

   public partial class Entities : DbContext
   {
       public override int SaveChanges()
       {
           var UserInfo = UserInfoContext.Current;
   
           // Call the original SaveChanges(), which will save both the changes made and the audit records
           return base.SaveChanges();
       }
   }