Collections ASP.NET MVC 4代码首先多对多添加到集合中

我使用ASP.NETMVC4代码优先模式作为数据库层。我在UserProfile和Task之间有一种多对多的关系。当我尝试将任务添加到用户的任务集合时，它会被添加，但如果我尝试查询它并查看它是否在那里，它不会显示

我的模型：

public class UserProfile
{
    [Key]
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int UserId { get; set; }
    public string UserName { get; set; }
    public string FirstName { get; set; }
    public string SirName { get; set; }
    public string Position { get; set; }
    public string Email { get; set; }
    public ICollection<TaskModels> Tasks {get; set; }
    public bool? isActive { get; set; }

    public UserProfile()
    {
        Tasks = new HashSet<TaskModels>();
    }
}

public class TaskModels
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }
    public DateTime? StartDate { get; set; }
    public DateTime? EndDate { get; set; }
    public ICollection<UserProfile> Employees { get; set; }
    public int TimeNeeded { get; set; }
    public int TimeWorked { get; set; }
    public string Status { get; set; }
    public bool isActive { get; set; }

    public TaskModels()
    {
        Employees = new HashSet<UserProfile>();
    }
}

public class WorkLogModels
{
    public int Id { get; set; }
    public UserProfile Author { get; set; }
    public DateTime TimeBeganWorking { get; set; }
    public int TimeWorkedOn { get; set; }
    public TaskModels Task { get; set; }
    public string Description { get; set; }
}

我已经为此奋斗了两天了

任何帮助都将不胜感激

编辑：

我不确定我是否讲清楚了。在WorkLog控制器的板条箱操作中，我试图将当前用户放入当前任务的集合中，反之亦然。它第一次工作正常，但如果我再次这样做，它将无法跳过if语句并再次尝试添加它，并引发异常：System.Data.SqlClient.SqlException。它试图将相同的记录添加到中间表中

    }

    public DbSet<UserProfile> UserProfiles { get; set; }
    public DbSet<TaskModels> Tasks { get; set; }
    public DbSet<WorkLogModels> WorkLogs { get; set; }
}

    [HttpPost]
    public ActionResult Create(WorkLogModels worklogmodels)
    {
        var tasks = db.Tasks.Where(x => x.Name == worklogmodels.Task.Name).SingleOrDefault();
        if (tasks == null)
        {
            return View(worklogmodels);
        }
        if (ModelState.IsValid)
        {
            var user = db.UserProfiles.Where(x => x.UserId == WebSecurity.CurrentUserId).FirstOrDefault();
            var task = db.Tasks.Where(x => x.Name == worklogmodels.Task.Name).FirstOrDefault();
            WorkLogModels log = new WorkLogModels();
            log.Description = worklogmodels.Description;
            log.TimeBeganWorking = worklogmodels.TimeBeganWorking;
            log.TimeWorkedOn = worklogmodels.TimeWorkedOn;
            log.Author = user;
            log.Task = task;
            db.WorkLogs.Add(log);

            if (!db.UserProfiles.Where(x => x.UserId == WebSecurity.CurrentUserId).First().Tasks.Any(x=> x.Name == worklogmodels.Task.Name))
            {
                db.UserProfiles.Where(x => x.UserId == WebSecurity.CurrentUserId).FirstOrDefault().Tasks.Add(task);
                db.Tasks.Where(x => x.Name == worklogmodels.Task.Name).FirstOrDefault().Employees.Add(user);
            }
            db.SaveChanges();
            return RedirectToAction("Index");
        }

        return View(worklogmodels);
    }