Set ASP.Net Forms label to Model Property value?

Question

I'm working with an ASP.NET Forms application where (for simplicity) I added Model properties [TotalService] & [PurchasedorReinstatedService] where I am storing the value from another Model into this property for use in the first Model.

I am then trying to reference this Model property and set an ASP Label .Text property to it. Problem is, I keep getting NullReferenceExceptions, specifically:

An exception of type 'System.NullReferenceException' occurred in PROJECT.dll but was not handled in user code

Additional information: Object reference not set to an instance of an object.

This is my custom control where I'm getting the error:

using PROJECT.Models.Default;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using PROJECT.Classes;

namespace PROJECT.CustomControls.Default
{
    public partial class YearsOfService : System.Web.UI.UserControl
    {
        public List<Years_Of_Service> yos { get; set; }
        public Years_Of_Service_Data yosd { get; set; }


        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                ApplyData();
            }
        }

        private void ApplyData()
        {
            salaryGridView.DataSource = yos;
            salaryGridView.DataBind();

            decimal totalService = 0;
            foreach (GridViewRow row in salaryGridView.Rows)
            {
                totalService += Convert.ToDecimal(row.Cells[1].Text);
            }

            if (yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault().ToString() != null) // NULL REFERENCE HERE
            {
                creditSalLabel.Text = yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault().ToString();
            }
            else
            {
                creditSalLabel.Text = String.Empty;
            }
        }
    }
}

This is my Years_Of_Service model:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace PROJECT.Models.Default
{
    public class Years_Of_Service
    {
        public int Year { get; set; }
        public string FiscalYear
        {
            get
            {
                return Year + "-" + (Year + 1);
            }
        }
        public decimal ServiceCredited { get; set; }
        public decimal Salary { get; set; }
        public string CoveredEmployer { get; set; }

        // New properties added for Label Values
        public string TotalService { get; set; }
        public string PurchasedorReinstatedService { get; set; }
    }
}

Years_Of_Service_Data Model:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace PROJECT.Models.Default
{
    public class Years_Of_Service_Data
    {
        public List<Years_Of_Service> YearsOfService { get; set; }
    }
}

and this is the bit of code in my Helper where I am reading from my database results ( Oracle Data Reader ) into my Model entity (I have confirmed the values are getting correctly added to the TotalService & PurchasedorReinstatedService properties):

            while (odr.Read())
            {
                Years_Of_Service yosRecord = new Years_Of_Service();

                yosRecord.Year = gh.GetSafeInt(odr, 0);
                yosRecord.ServiceCredited = gh.ConvertNullDecimal(odr.GetValue(1));
                yosRecord.Salary = gh.ConvertNullDecimal(odr.GetValue(2));
                yosRecord.CoveredEmployer = gh.GetSafeString(odr, 3);

                // Use the Default Info Model Class - At_A_Glance Model properties to fill these properties for text labels.
                yosRecord.TotalService = defInfoOasis.At_A_Glance.CreditTotal.ToString("N5");
                yosRecord.PurchasedorReinstatedService = defInfoOasis.At_A_Glance.TotalPurchase.ToString("N5");
                yos.Add(yosRecord);
            }

Originally I tried the following, also getting the FirstOrDefault() entity, with the same results of NullReferenceException :

creditSalLabel.Text = yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault() != null ? yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault().ToString() : String.Empty;

purchaseCreditLabel.Text = yosd.YearsOfService.OrderByDescending(y => y.PurchasedorReinstatedService).FirstOrDefault() != null ? yosd.YearsOfService.OrderByDescending(y => y.PurchasedorReinstatedService).FirstOrDefault().ToString() : string.Empty;

Anyone have any ideas for how I can set my Label.Text property to my (any entity) Model properties [TotalService] & [PurchasedorReinstatedService] ? With the way I'm setting the property, each entity in the referenced model classes will have the same value for these 2 properties.

Answer 1

My guess is you are getting back the default which is null

yosd.YearsOfService.OrderByDescending(y => y.TotalService).FirstOrDefault()

Then you are doing the ToString() on the null.

If that is not it, I would look at yosd for null or yosd.YearsOfService for null.