ASP.NET MVC 5页面挂起db调用

Question

I'm trying to get up and running with an MVC 5 project using ASP.NET Identity 2.0. My starting point is the example app in this tutorial . My initial page is Home/Index. When I try to do a search (expecting a null return value) the app simply hangs and I can't figure out why. Instantiation of the db context is causing the Seed() method to be called, which seems normal, but then it hangs on the roleManager.FindByName(roleName) call (I've commented it in the code below). Pausing the debugger showed where it was stuck but I don't know where to go from there. Relevant classes are as follows.

Controller:

public class HomeController : ApplicationController
{         
    public ActionResult Index()
    {
        var user = db.Users.Find("dummyVal");

        return View();
    }

    [Authorize]
    public ActionResult About()
    {
        ViewBag.Message = "Your app description page.";

        return View();
    }

    public ActionResult Contact()
    {
        ViewBag.Message = "Your contact page.";

        return View();
    }
}

Base Controller:

public abstract class ApplicationController : Controller
{
    protected ApplicationDbContext db;

    public ApplicationController()
    {
        db = new ApplicationDbContext();
    }
}

DB Initializer:

public class ApplicationDbInitializer : DropCreateDatabaseAlways<ApplicationDbContext> 
{
    protected override void Seed(ApplicationDbContext context) {
        InitializeIdentityForEF(context);
        base.Seed(context);
    }

    //Create User=Admin@Admin.com with password=Admin@123456 in the Admin role        
    public static void InitializeIdentityForEF(ApplicationDbContext db) {
        var userManager = HttpContext.Current.GetOwinContext().GetUserManager<ApplicationUserManager>();
        var roleManager = HttpContext.Current.GetOwinContext().Get<ApplicationRoleManager>();
        const string name = "admin@example.com";
        const string password = "Admin@123456";
        const string roleName = "Admin";

        //Create Role Admin if it does not exist
        // EXECUTION HANGS ON THIS CALL...
        var role = roleManager.FindByName(roleName);
        if (role == null) {
            role = new IdentityRole(roleName);
            var roleresult = roleManager.Create(role);
        }

        var user = userManager.FindByName(name);
        if (user == null) {
            user = new ApplicationUser { UserName = name, Email = name };
            var result = userManager.Create(user, password);
            result = userManager.SetLockoutEnabled(user.Id, false);
        }

        // Add user admin to Role Admin if not already added
        var rolesForUser = userManager.GetRoles(user.Id);
        if (!rolesForUser.Contains(role.Name)) {
            var result = userManager.AddToRole(user.Id, role.Name);
        }

        // Create dummy user
        const string dummyUserName = "PeterVenkman";
        const string dummyUserPwd = "gf%^^ftf83X";

        var dummyUser = userManager.FindByName(dummyUserName);
        if (dummyUser == null) { 
            dummyUser = new ApplicationUser { UserName = dummyUserName, Email = dummyUserName };
            var result = userManager.Create(dummyUser, dummyUserPwd);
            result = userManager.SetLockoutEnabled(dummyUser.Id, false);
        }
    }
}

Answer 1

The error is because you are instantiating the dbContext object in the controller and not getting it from the owin context. The presence of two different context objects one in the controller and one in the startup working on the same db is causing this deadlock. Simplest way to resolve this is replace the code

            db = new ApplicationDbContext();

with

db = System.Web.HttpContext.Current.GetOwinContext().Get<ApplicationDbContext>();

fixes the issue

Answer 2

I had the same problem and this is how I fixed it.

1. Delete your current database (I was using .mdf)
2. Create a new database
3. Clean and rebuild
4. Update database - if needed -

Unfortunately, I do not know the source of the problem. Please edit the answer/post a comment if you know :)

For other people with the same issue, make sure the username/password in ApplicationDbInitializer are valid. It will hang if you set the admin password to 123 for example.

Edit: This post provides an explanation + answer http://forums.asp.net/post/5802779.aspx

Answer 3

Suhas Joshi has the correct answer. The ApplicationDbContext object should be in essence a singleton that is managed by the "Microsoft ASPNET Identity Owin" package (installed using NuGet). When you manually create a new instance of it in your ApplicationController there is contention for the same resource causing this deadlock.

Note that the "Get()" extension used comes from the following library which you must have a reference to in your ApplicationContext class.

using Microsoft.AspNet.Identity.Owin; 

Thanks Suhas Joshi for pointing this out as it saved me greatly. I would have just up-voted your answer, but unfortunately I don't have a strong enough reputation yet :).