c# - SqlException:Cannot insert the value NULL into column 'IstanbulCardId'

Question

I want to update just the balance column, but I get an error:

An unhandled exception occurred while processing the request. SqlException:Cannot insert the value NULL into column 'IstanbulCardId', table 'Transportation.dbo.TbIstanbulCard'; column does not allow nulls. INSERT fails. The statement has been terminated

Tb Istanbul:

public partial class TbIstanbulCard
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int IstanbulCardId { get; set; }
        public decimal? Balance { get; set; }
        public int CustomerId { get; set; }
        public virtual TbCustomer Customer { get; set; }
    }

VmIstanul:

public class VmIstanbul :TbIstanbulCard
    {
        public string CustomerType { get; set; }
        public string CustomerName { get; set; }
        public double TransportNumber { get; set; }
        public double NumberOfStops { get; set; }
        public string Vehicles { get; set; }
        public double AvailableBalance { get; set; }
        public double DeductedAmount { get; set; }
    }

Action Controller:

public async Task<IActionResult> CalcIstanbul(VmIstanbul card)
        { 
            if (card.Vehicles == "Bus")
            {
                customer.IstanbulBus(card);
                Convert.ToDecimal(ViewBag.balance = customer.IstanbulBalance());
                ViewBag.amount = customer.IstanbulAmountDeducted();
                var update = new TbIstanbulCard()
                {
                    IstanbulCardId = card.IstanbulCardId,
                    Balance = ViewBag.balance
                };
                using (var edit = ctx) {
                ctx.TbIstanbulCards.Attach(update);
                ctx.Entry(update).Property(x => x.Balance).IsModified = true;
                ctx.SaveChanges();
                }
            }
            else if (card.Vehicles == "MetroBus")
            {
                customer.IstanbulMetroBus(card);
                ViewBag.balance = customer.IstanbulBalance();
                ViewBag.amount = customer.IstanbulAmountDeducted();
            }
            return View();
        }

View Istanbul:

@model Transportation.Vm.VmIstanbul
    <div class="contact_section_2">
        <div class="container">
            <div class="row">
                <div class="col-md-12">
                    <div class="input_main">
                        <div class="container">
                            <form asp-controller="Customer" asp-action="CalcIstanbul">
                                <div class="form-group">
                                    <label for="departmentsDropdown"><b>Card</b></label>
                                    <select asp-for="IstanbulCardId" style=" background: #ececec; border: none; color: #000; width: 100%; height: 55px; font-size: 22px; padding: 0px; border-radius: 10px; margin-top: 6px;" onchange="getValue()" id="departmentsDropdown" name="departmentsDropdown"></select><br />
                                </div>
                                <div class="form-group">
                                    <label><b>Balance</b></label>
                                    <input asp-for="Balance" class="email-bt" type="text" value="" id="show" />
                                </div>
                                <div class="form-group">
                                    <label><b>Customer Type</b></label>
                                    <input asp-for="CustomerType" class="email-bt" type="text" value="" id="sshow" />
                                </div>

                                <div class="form-group">
                                    <select asp-for="Vehicles"   id="service" style=" background: #ececec; border: none; color: #000; width: 100%; height: 55px; font-size: 22px; padding: 0px; border-radius: 10px; margin-top: 6px;">
                                        <option>Select Vehicle Type</option>
                                        <option value="MetroBus" data-target="devices" id="screen">MetroBus</option>
                                        <option value="Bus" data-target="comp" id="comp">Bus</option>
                                    </select>
                                </div>
                                <div class="form-group">
                                    <div style="display:none" id="service-devices">
                                        <select asp-for="NumberOfStops"   id="devices" style=" background: #ececec; border: none; color: #000; width: 100%; height: 55px; font-size: 22px; padding: 0px; border-radius: 10px; margin-top: 6px;">
                                            <option>Please Select The Number of Stops</option>
                                            <option value="3">3</option>
                                            <option value="9">9</option>
                                            <option value="15">15</option>
                                            <option value="21">21</option>
                                            <option value="27">27</option>
                                            <option value="33">33</option>
                                        </select>
                                    </div>
                                </div>
                                <div class="form-group">
                                    <div style="display:none" id="service-comp">
                                        <select asp-for="TransportNumber"   id="compwork" style=" background: #ececec; border: none; color: #000; width: 100%; height: 55px; font-size: 22px; padding: 0px; border-radius: 10px; margin-top: 6px;">
                                            <option>Please Select Your Transport Number</option>
                                            <option value="0">0</option>
                                            <option value="1">1</option>
                                            <option value="2">2</option>
                                            <option value="3">3</option>
                                            <option value="4">4</option>
                                            <option value="5">5</option>
                                        </select>
                                    </div>
                                </div>

                                <div class="send_btn">
                                    <button type="submit" class="btn btn-success mr-1 mb-1" asp-controller="Customer" asp-action="CalcIstanbul">Calculate</button>
                                </div>
                                <div class="col-12">
                                    <div class="form-group row">
                                        <div class="col-md-2">
                                            <span>Deducted Amount</span>
                                        </div>
                                        <div class="col-md-8">
                                            <input  class="form-control" placeholder="@ViewBag.amount">
                                        </div>
                                    </div>
                                </div>
                                <div class="col-12">
                                    <div class="form-group row">
                                        <div class="col-md-2">
                                            <span>Available Balance</span>
                                        </div>
                                        <div class="col-md-8">
                                            <input  type="number"  class="form-control" placeholder="@ViewBag.balance">
                                        </div>
                                    </div>
                                </div>

                            </form>

                        </div>
                    </div>
                </div>

            </div>
        </div>
    </div>



    @section Scripts{
        <script src="https://code.jquery.com/jquery-1.10.2.min.js"></script>
        <script type="text/javascript">
            $(document).ready(function () {
                $.ajax({
                    type: "GET",
                    url: "/Customer/SelectIstanbul",
                    success: function (data) {
                        console.log(data);
                        var s = '<option  value="-1">Please Select a Card id</option>';
                        for (var i = 0; i < data.length; i++) {

                            s += '<option  value="' + data[i].customerType + "," + data[i].balance + '">' + data[i].istanbulCardId + '</option>';

                        }
                        $("#departmentsDropdown").html(s);
                    }
                })
            })

            function getValue() {
                var myVal = $("#departmentsDropdown").val();
                $("#show").val(myVal.split(",")[1]);
                $("#sshow").val(myVal.split(",")[0]);

            }

            $(document).ready(function () {
                $('select').on('change', function () {
                    var target = $(this).find(":selected").attr("data-target");
                    var id = $(this).attr("id");
                    $("div[id^='" + id + "']").hide();
                    $("#" + id + "-" + target).show();
                });
            });
        </script>
    }

question from:https://stackoverflow.com/questions/65920429/sqlexceptioncannot-insert-the-value-null-into-column-istanbulcardid

Answer 1

Looks like the foreign key is not nullable. Try

public partial class TbIstanbulCard
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int IstanbulCardId { get; set; }
    public decimal? Balance { get; set; }
    public int? CustomerId { get; set; }
    public virtual TbCustomer Customer { get; set; }
}