ASP.NET Core NullReferenceException After form is posted

Question

I am getting NullReferenceException when I post the form back to the server. I am using ADO.NET with ASP.NET Core 3

Below is the Model for Campgrounds:

public class Campground
{
    public int ID { get; set; }

    [Required]
    [MaxLength(200)]
    [Display(Name = "Campground Name")]
    public string CampgroundName { get; set; }

    [Required]
    public int State { get; set; }
    public List<State> States { get; set; }

    [Required]
    public int Peak { get; set; }
    public List<Month> Months { get; set; }

    [Required]
    public string Overview { get; set; }

    [Required]
    [Display(Name = "Season Date From")]
    [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:MM/dd/YYYY}")]
    [DataType(DataType.Date)]
    public DateTime? SeasonDateFrom { get; set; }

    [Required]
    [Display(Name = "Season Date To")]
    [DisplayFormat(ApplyFormatInEditMode = true, DataFormatString = "{0:MM/dd/YYYY}")]
    [DataType(DataType.Date)]
    public DateTime SeasonDateTo { get; set; }


    [Display(Name = "Natural Features")]
    public string NaturalFeatures { get; set; }

    public string Recreation { get; set; }

    public string Facilities { get; set; }

    [Required]
    [Display(Name = "Campground Photo")]
    public string ImagePath { get; set; }
}

I also have created a ViewModel and I called it CampgroundDetails:

 public class CampgroundDetails : Campground
{
    [Required]
    [Display(Name = "Campground Image")]
    public IFormFile Photo { get; set; }
}

I have tried different approaches but I am not able to move on because of this error. Your help is much appreciated.

Here is the HttpGet of Create Method:

 [HttpGet]
    public IActionResult Create()
    {
        CampgroundDetails campgroundDetails = new CampgroundDetails();
        List<State> states = new List<State>();
        List<Month> months = new List<Month>();

        using (SqlConnection connection = new SqlConnection(ConnectionString.DBCS))
        {
            using (SqlCommand command = new SqlCommand("sp_GetStates_Months", connection))
            {
                command.CommandType = CommandType.StoredProcedure;
                if (connection.State == ConnectionState.Closed)
                    connection.Open();
                using (SqlDataAdapter ada = new SqlDataAdapter(command))
                {
                    DataSet ds = new DataSet();
                    ada.Fill(ds);

                    DataTable statesDataTable = ds.Tables[0];
                    foreach(DataRow row in statesDataTable.Rows)
                    {
                        states.Add(new State()
                        {
                            ID = Convert.ToInt32(row["ID"]),
                            StateName = row["StateName"].ToString()
                        });
                    }
                    campgroundDetails.States = states;

                    DataTable monthsDataTable = ds.Tables[1];
                    foreach(DataRow row in monthsDataTable.Rows)
                    {
                        months.Add(new Month()
                        {
                            ID = Convert.ToInt32(row["ID"]),
                            MonthName = row["Month"].ToString()
                        }); ;
                    }
                    campgroundDetails.Months = months;
                }
            }
        }
        return View(campgroundDetails);
    }

Here is the HttpPost of Create Method:

[HttpPost]
    public IActionResult Create(CampgroundDetails campgroundDetails)
    {
        if (ModelState.IsValid)
        {
            string filePath = UploadFile(campgroundDetails);

            using (SqlConnection connection = new SqlConnection(ConnectionString.DBCS))
            {
                using (SqlCommand command = new SqlCommand("sp_InsertNewCampground", connection))
                {
                    command.CommandType = CommandType.StoredProcedure;
                    command.Parameters.AddWithValue("@CampgroundName", campgroundDetails.CampgroundName);
                    command.Parameters.AddWithValue("@State", campgroundDetails.State);
                    command.Parameters.AddWithValue("@Peak", campgroundDetails.Peak);
                    command.Parameters.AddWithValue("@SeasonDateFrom", campgroundDetails.SeasonDateFrom);
                    command.Parameters.AddWithValue("@SeasonDateTo", campgroundDetails.SeasonDateTo);
                    command.Parameters.AddWithValue("@NaturalFeatures", campgroundDetails.NaturalFeatures ?? "");
                    command.Parameters.AddWithValue("@Recreation", campgroundDetails.Recreation ?? "");
                    command.Parameters.AddWithValue("@Facilities", campgroundDetails.Facilities ?? "");
                    command.Parameters.AddWithValue("@ImagePath", filePath);
                    command.Parameters.AddWithValue("@Overview", campgroundDetails.Overview);

                    if (connection.State == ConnectionState.Closed)
                        connection.Open();

                    command.ExecuteNonQuery();
                }
            }
            return RedirectToAction("index", "home");
        }

        return View();
    }

Here is the error I am getting:

Please post the actual exception. Without it all we are looking at is some class definitions. Also, please post the controller method that the form POST is being sent to. — gabriel.hayes, Jan 31 '20 at 18:01
it seems that your problem is SeasonDateFrom where you make it required and nullable. — divyang4481, Jan 31 '20 at 18:03
Your error shows that it tried to select a state on the states view model but there is nothing to select. Something is null. Are you sure when you did a get GET that your model was populated correctly? — LukePerrin, Jan 31 '20 at 18:20
When I traced my code, after postback my form is never valid — Ali Sultan, Jan 31 '20 at 18:30
Does this answer your question? [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — Ian Kemp, Jan 31 '20 at 20:44

score 0 · Answer 1 · answered Jan 31 '20 at 18:54

0

I have found a solution to my issue, it is because I made the file upload mandatory

answered Jan 31 '20 at 18:54

Ali Sultan

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ASP.NET Core NullReferenceException After form is posted

1 Answers1