Object reference not set to an instance of an object in view model

Question

I get this error:

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 
Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.
Source Error: 
Line 251:            ManageAccount.Instance.GetUserAccounts(username), "accountID", "name", accountFrom);
Line 252:
Line 253:            Currencies = new SelectList(
Line 254:            ManageCurrency.Instance.getCurrencies(), "id", "name",_Account.currency1.id);
Line 255:

It gives the error in this viewModel

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.ComponentModel.DataAnnotations;
using Common;
using Business;
using System.Web.Mvc;
using System.Web.Security;
using System.Runtime.Remoting.Contexts;

namespace internetBankingApplication.ViewModel
{

    public class NewFixedAccountViewModel
    {
        private account _Account { get; set; }

        private fixedAccount _FixedAccount { get; set; }



        public SelectList AccountTypes { get; set; }

        public SelectList Durations { get; set; }

        public SelectList AccountFromList { get; set; }

        public SelectList Currencies { get; set; }

        public int ID
        {
            get
            {
                return _Account.accountID;
            }
        }

        [Required]
        [Display(Name = "Account Name")]
        public string Name
        {
            get
            {
                return _Account.name;
            }
            set
            {
                _Account.name = value;
            }
        }

        [Required]
        [Display(Name = "Account From")]
        public int accountFrom { get;set;}



        public string AccountFromName
        {
            get
            {
                string result = string.Empty;
                try
                {
                    result = ManageAccount.Instance.GetAccountBYID(accountFrom).name;
                }
                catch { }
                return result;
            }
        }



        [Required]
        [Display(Name = "Duration")]
        public int duration
        {
            get
            {
                return _FixedAccount.duration;
            }
            set
            {
                _FixedAccount.duration = value;
            }
        }

        public string durationName
        {
            get
            {
                string result = string.Empty;
                try
                {
                    result = ManageDuration.Instance.GetDurationById(_FixedAccount.duration).duration1;
                }
                catch { }
                return result;
            }
        }

        [Required]
        [Display(Name = "Available Balance")]
        public decimal AvailableBalance
        {
            get
            {
                return _Account.availableBalance;
            }
            set
            {
                _Account.availableBalance = value;
            }
        }

        [Required]
        [Display(Name = "Currency")]
        public int currency
        {
            get
            {
                return _Account.currency;
            }
            set
            {
                _Account.currency = value;
            }
        }

        public string CurrencyName
        {
            get
            {
                string result = string.Empty;
                try
                {
                    result = ManageCurrency.Instance.getTypesByID(_Account.currency).name;
                }
                catch { }
                return result;
            }
        }


        [Required]
        [Display(Name = "Account Description")]
        public string Description
        {
            get
            {
                return _Account.description;
            }
            set
            {
                _Account.description = value;
            }
        }


        [Required]
        [Display(Name = "Account Renew")]
        public bool renew
        {
            get
            {
                if (_FixedAccount.renew == 0)
                {
                    return false;
                }
                return true;
            }
            set
            {
                if (value == false)
                {
                    _FixedAccount.renew = 0;
                }
                else
                {

                    _FixedAccount.renew = 1;
                }
            }
        }


        public NewFixedAccountViewModel()
        {
           // AccountTypes = new SelectList(
           //ManageAccountType.Instance.getTypes(), "id", "type", _Account.typeID);

            string username = HttpContext.Current.User.Identity.Name.ToString();
            AccountFromList = new SelectList(
            ManageAccount.Instance.GetUserAccounts(username), "accountID", "name", accountFrom);

            **Currencies = new SelectList(
            ManageCurrency.Instance.getCurrencies(), "id", "name",_Account.currency1.id);** //Giving the error

            Durations = new SelectList(
            ManageDuration.Instance.GetAllDurations(), "id", "duration", _FixedAccount.duration);



        }

        public NewFixedAccountViewModel(string username)
        {
            AccountTypes = new SelectList(
            ManageAccountType.Instance.getTypes(), "id", "type", _Account.typeID);


            AccountFromList = new SelectList(
            ManageAccount.Instance.GetUserAccounts(username), "accountID", "name", accountFrom);

            Currencies = new SelectList(
            ManageCurrency.Instance.getCurrencies(), "id", "name", _Account.currency);

            Durations = new SelectList(
            ManageDuration.Instance.GetAllDurations(), "id", "duration", _FixedAccount.duration);


        }

        public NewFixedAccountViewModel(int accountID, string username)
        {
            _Account = ManageAccount.Instance.GetAccountBYID(accountID);

            _FixedAccount = ManageFixedAccount.Instance.GetFixedAccountByID(accountID);

            AccountFromList = new SelectList(
            ManageAccount.Instance.GetUserAccounts(username), "accountID", "name", accountFrom);

            AccountTypes = new SelectList(
            ManageAccountType.Instance.getTypes(), "id", "type", _Account.accountType);

            Currencies = new SelectList(
            ManageCurrency.Instance.getCurrencies(), "id", "name", _Account.currency);

            Durations = new SelectList(
            ManageDuration.Instance.GetAllDurations(), "id", "duration", _FixedAccount.duration);


        }
    }
}

Answer 1

The error message you are getting means that you are trying to call a method or property on a null value - which you can't do.

From what I can see, either ManageCurrency is null or ManageCurrency.Instance is null.

If ManageCurrency is null the call to the Property Instance fails, as null objects have no methods or properties. Similarly, if ManageCurrency.Instance is null, the call to the Method getCurrencies fails for the same reason.

In any case - this is not too hard to debug. As skumar suggests, set a breakpoint on that line, run in debug mode, and see where the null value is, and then work backwards to discover why the value is null.

Answer 2

The username you are passing in the following code could be Empty or Invalid. That is why it returns NULL and above exception occurs.

AccountFromList = new SelectList(
            ManageAccount.Instance.GetUserAccounts(username), "accountID", "name", accountFrom);