OWIN - 未将对象引用设置为对象的实例

Question

我正在使用asp.net mvc 5开发一个Web应用程序。但是我在玩用户帐户时遇到了一些错误。我创建了一个用户帐户，我想删除它，但在使用ajax-jquery时遇到以下问题。我试图使用ajax请求删除用户帐户，但它为空对象引用提供错误，因为由于ajax调用而未启动Owin Context。

 public class AdmissionsController : Controller
 {
    private ApplicationSignInManager _signInManager;
    private ApplicationUserManager _userManager;

    public AdmissionsController()
    {

    }

    public AdmissionsController(ApplicationUserManager userManager, ApplicationSignInManager signInManager)
    {
        UserManager = userManager;
        SignInManager = signInManager;
    }

    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;
        }
    }




    //function to delete user account
    public async Task<object> DeleteUser(string id)
    {
        ApplicationDbContext context = new ApplicationDbContext();

        if (id == null)
        {
            return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
        }

        var user = await _userManager.FindByIdAsync(id);
        var logins = user.Logins;
        var rolesForUser = await _userManager.GetRolesAsync(id);

        using (var transaction = context.Database.BeginTransaction())
        {
            foreach (var login in logins.ToList())
            {
                await _userManager.RemoveLoginAsync(login.UserId, new UserLoginInfo(login.LoginProvider, login.ProviderKey));
            }

            if (rolesForUser.Count() > 0)
            {
                foreach (var item in rolesForUser.ToList())
                {
                    // item should be the name of the role
                    var result = await _userManager.RemoveFromRoleAsync(user.Id, item);
                }
            }

            await _userManager.DeleteAsync(user);
            transaction.Commit();
        }

        return new{success=true};

    }



}

我的ajax电话如下：

        var userid = $(this).attr("data-StudentId");
        var success = false;




        $.ajax({
            method: "Get",
            url: "/Area/Admissions/DeleteUser",
            data: { "id": userid },
            success: function (response) {
                if (response.Success == true) {
                    success = true;

                }
                else if (response.Success == false) {
                       //window.location.reload();
                }
            },
            error: function (response) {
                notificationMSG("fa fa-thumbs-up", "error", "Error", response.message);
            }

        });

我该如何解决这个问题？我在以下行收到错误：

  var user = await _userManager.FindByIdAsync(id);

Answer 1

这只是一个疯狂的猜测，但在我看来，你没有实例化_userManager。您有一个相应的属性来进行此创建。但是，在有错误的行中，您使用私有字段。尝试使用该属性：

var user = await UserManager.FindByIdAsync(id);

这将调用getter，从owin上下文中获取此管理器。