MVC5帐户控制空引用异常 [英] MVC5 Account Controller null reference exception

问题描述

我想实现用户角色到我的MVC Web应用程序。不过我上线得到一个空的异常返回_userManager？ 。HttpContext.GetOwinContext（）GetUserManager＆LT; ApplicationUserManager＆GT;（）; 在我的帐户控制器。

I am trying to implement user roles into my MVC web application. However I am getting a null exception on the line return _userManager ?? HttpContext.GetOwinContext().GetUserManager<ApplicationUserManager>(); in my account controller.

帐户控制器

[Authorize]
public class AccountController : Controller
{
    private ApplicationSignInManager _signInManager;
    private ApplicationUserManager _userManager;
    private ApplicationRoleManager _roleManager; 

    public AccountController(){}

    public AccountController(ApplicationUserManager userManager, ApplicationSignInManager signInManager, ApplicationRoleManager roleManager)
    {   UserManager = userManager;
        SignInManager = signInManager;
        RoleManager = roleManager; }
    public ApplicationRoleManager RoleManager
    {
        get { return _roleManager ?? HttpContext.GetOwinContext().Get<ApplicationRoleManager>(); }
        private set { _roleManager = value; }
    }

    public ApplicationSignInManager SignInManager
    {
        get { return _signInManager ?? HttpContext.GetOwinContext().Get<ApplicationSignInManager>(); }
        private set  { _signInManager = value; }
    }

    public ApplicationUserManager UserManager
    {
        get { return _userManager ?? HttpContext.GetOwinContext().GetUserManager<ApplicationUserManager>(); }
        private set {_userManager = value; }
    }

的ActionResult将触发用户到角色的添加。

ActionResult that will trigger the adding of the user to the role.

    [System.Web.Mvc.HttpPost]
    [ValidateAntiForgeryToken]
    public ActionResult RoleAddToUser(string UserName, string RoleName)
    {
        ApplicationUser user = context.Users.FirstOrDefault(u => u.UserName.Equals(UserName, StringComparison.CurrentCultureIgnoreCase));
        var account = new AccountController();
        if (user != null) account.UserManager.AddToRole(user.Id, RoleName);
        var list = context.Roles.OrderBy(r => r.Name).ToList().Select(rr => new SelectListItem { Value = rr.Name.ToString(), Text = rr.Name }).ToList();
        ViewBag.Roles = list;
        return View("ManageUserRoles");
    }

Startup.Auth确实包含

Startup.Auth does contain

        app.CreatePerOwinContext(ApplicationDbContext.Create);
        app.CreatePerOwinContext<ApplicationRoleManager>(ApplicationRoleManager.Create);
        app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
        app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);

身份配置

    // Configure the application sign-in manager which is used in this application.
public class ApplicationSignInManager : SignInManager<ApplicationUser, string>
{
    public ApplicationSignInManager(ApplicationUserManager userManager, IAuthenticationManager authenticationManager)
        : base(userManager, authenticationManager)
    {
    }

    public override Task<ClaimsIdentity> CreateUserIdentityAsync(ApplicationUser user)
    { return user.GenerateUserIdentityAsync((ApplicationUserManager)UserManager); }

    public static ApplicationSignInManager Create(IdentityFactoryOptions<ApplicationSignInManager> options, IOwinContext context)
    { return new ApplicationSignInManager(context.GetUserManager<ApplicationUserManager>(), context.Authentication); }
}
public class ApplicationRoleManager : RoleManager<IdentityRole>
{
    public ApplicationRoleManager(IRoleStore<IdentityRole, string> roleStore)
        : base(roleStore) { }

    public static ApplicationRoleManager Create(IdentityFactoryOptions<ApplicationRoleManager> options, IOwinContext context)
    {
        return new ApplicationRoleManager(new RoleStore<IdentityRole>(context.Get<ApplicationDbContext>()));
    }
}

在哪里空引用来自何处？在code我双重检查该用户存在。

Where is the null reference coming from? In the code I am double checking that the user exists.

感谢

推荐答案

这无疑是有问题的行...

These are undoubtedly the offending lines...

var account = new AccountController();
if (user != null) account.UserManager.AddToRole(user.Id, RoleName);

控制器并不意味着以这种方式被实例化，因为它们严重依赖于当前的HTTP请求（因此 HttpContext的）。

在 HttpContext.GetOwinContext（）GetUserManager＆LT; ApplicationUserManager＆GT;（）; 被击中，的HttpContext 为null，因为没有上下文。

When HttpContext.GetOwinContext().GetUserManager<ApplicationUserManager>(); gets hit, HttpContext is null because there is no context.

您可以简单地把你的控制器相同的属性，您试图访问的UserManager。这工作，因为OwinContext是在整个应用程序共享。

You can simply put the same property in your controller where you are trying to access the UserManager. This works because the OwinContext is shared across your entire application.

public class HomeController : Controller
{
    public ApplicationUserManager UserManager
    {
        get { return _userManager ?? HttpContext.GetOwinContext().GetUserManager<ApplicationUserManager>(); }
        private set {_userManager = value; }
    }

    public ActionResult RoleAddToUser(string UserName, string RoleName)
    {
        ApplicationUser user = context.Users.FirstOrDefault(u => u.UserName.Equals(UserName, StringComparison.CurrentCultureIgnoreCase));
        if (user != null) UserManager.AddToRole(user.Id, RoleName);

        //Other code...

        return View("ManageUserRoles");
    }
}

如果你想获得真正看中的，声明 BaseController 从控制器继承，把的UserManager 属性里面，有你的所有其他控制器从你的基地继承。

And if you want to get really fancy, declare a BaseController that inherits from Controller, put the UserManager property inside, and have all your other controllers inherit from your base.

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