在mvc项目中插入错误：{“对象引用未设置为对象的实例。”}

Question

i am working in mvc i want do save the details.. here i have a error.. controller

public ActionResult Edit(FormCollection frm)
    {
        StaffDetails sdtl=new StaffDetails();
        int UnvId = int.Parse(TempData["UnvID1"].ToString());
        sdtl.UnvId = UnvId;
        //sdtl.UnvId = int.Parse(TempData["UnvID"].ToString());
        string SportsName = frm["SportsAffliation"];
        var SpotsID = Db.SportsCodes.Where(s => s.SportsName == SportsName).FirstOrDefault();
        sdtl.SportsID = SpotsID.SportsCodeID;
        sdtl.Name = frm["name"];
        sdtl.Address.Street = frm["street"];
        sdtl.Address.City = frm["city"];
        sdtl.Address.State = frm["state"];
        sdtl.Address.PostalCode = frm["zip"];
        sdtl.Address.Country = frm["country"];
        sdtl.Email = frm["Email"];
        sdtl.Phone = frm["Phone"];
        sdtl.SportsAffliation = frm["SportsAffliation"];
        Db.Entry(sdtl).State = System.Data.Entity.EntityState.Modified;
        Db.SaveChanges();
        //return RedirectToAction("Edit", new { id = cohid, tab = 0 });
        return View();
    }

Domain

 public class StaffDetails
    {
        [Key]
        public int StaffId { get; set; }
        public int UnvId { get; set; }
        public University University { get; set; }
        public int SportsID { get; set; }
        public SportsCode SportsCode { get; set; }
        public int SportsGroupId { get; set; }
        public SportsGroup SportsGroup { get; set; }
        public int CoachingStaffId { get; set; }
        public CoachingStaff CoachingStaff { get; set; }
        public string Name { get; set; }
        public string SportsAffliation { get; set; }
        public string Email { get; set; }
        public string Phone { get; set; }
        public string OrganizationalLeader { get; set; }
        public Address Address { get; set; }
    }

error in below line from controller.. error only from sdtl.address...

sdtl.Address.Street = frm["street"];
    sdtl.Address.City = frm["city"];
    sdtl.Address.State = frm["state"];
    sdtl.Address.PostalCode = frm["zip"];
    sdtl.Address.Country = frm["country"];

error is {"Object reference not set to an instance of an object."}

i thing this a logical problem but i can't find because of i am new in mvc..can you solve this problem

Answer 1

You can either new the address object up in the constructor:

public StaffDetails()
{
    Address = new Address();
}

Or new address up in the Edit action in the controller.

public ActionResult Edit(FormCollection frm)
{
    StaffDetails sdtl=new StaffDetails() { Address = new Address() };
    // Rest of code 
}

This way would mean that you have to new up the Address object each time you use StaffDetails.

Answer 2

Add a constructor to your class and initialize the Address proeperty:

public StaffDetails()
{
    Address = new Address();
}

Answer 3

i think you should make a constructor for StaffDetails. in constructor you should initialize objects like address. i mean when you use StaffDetails sdtl=new StaffDetails(); this line it creates an StaffDetails object but Address object inside sdtl is still null.

Answer 4

you should create new instance from Address in Constractor StaffDetails :

public class StaffDetails
{

    public StaffDetails()
    {
      this.Address = new Address();
    }

    [Key]
    public int StaffId { get; set; }
    public int UnvId { get; set; }
    public University University { get; set; }
    public int SportsID { get; set; }
    public SportsCode SportsCode { get; set; }
    public int SportsGroupId { get; set; }
    public SportsGroup SportsGroup { get; set; }
    public int CoachingStaffId { get; set; }
    public CoachingStaff CoachingStaff { get; set; }
    public string Name { get; set; }
    public string SportsAffliation { get; set; }
    public string Email { get; set; }
    public string Phone { get; set; }
    public string OrganizationalLeader { get; set; }
    public Address Address { get; set; }
}