Unable to update status column in ASP.NET MVC view

Question

I am working on creating a web application for Hospital Management where admin need to approve the Patient/Doctor registration. I have created registration table and set status for each record to 0 until admin approves it. I want to change the column to 1 when admin approves the registration. I have written the approve view and once admin click it 0 should change to 1. But I am getting the validation error.

Attaching my code

using AgileProject_DMC.Models;
using System;
using System.Collections.Generic;
using System.Data.Entity;
using System.Linq;
using System.Web;
using System.Web.DynamicData;
using System.Web.Mvc;

namespace AgileProject_DMC.Controllers
{
    public class AdminApproveController : Controller
    {
    // GET: AdminApproving
    public ActionResult PatientDetails()
    {
        using(RegistrationEntities6 dbModel =new RegistrationEntities6() )
        {
            return View(dbModel.PatientRegistrationTables.Where(x => x.IsStatus==0).ToList());
        }
        return View();
    }
    public ActionResult PatientApprove(int id)
    {
        RegistrationEntities6 contextObject = new RegistrationEntities6();
        //contextObject.Database.ExecuteSqlCommand("Update PatientRegistrationTable SET IsStatus = 1 Where PatientId={0 }", id);
        var acceptStatus = contextObject.PatientRegistrationTables.Find(id);
        acceptStatus.IsStatus = 1;
        contextObject.SaveChanges();
        return RedirectToAction("PatientDetails");

and Table.cs file is

namespace AgileProject_DMC.Models
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity;

    public partial class PatientRegistrationTable
    {
        [DatabaseGenerated(DatabaseGeneratedOption.None)]
        public int PatientId { get; set; }

        [DisplayName("First Name")]
        [Required(AllowEmptyStrings = false, ErrorMessage = "This field is required")]
        public string FirstName { get; set; }

        [DisplayName("Last Name")]
        [Required(AllowEmptyStrings = false, ErrorMessage = "This field is required")]
        public string LastName { get; set; }

        [Required(ErrorMessage = "This field is required")]
        public Nullable<int> Age { get; set; }

        [Required(ErrorMessage = "This field is required")]
        public string Gender { get; set; }

        [Required(ErrorMessage = "This field is required")]
        [DisplayName("Contact Number")]
        public Nullable<long> ContactNumber { get; set; }

        [DisplayName("User Name")]
        [Required(AllowEmptyStrings = false, ErrorMessage = "This field is required")]
        public string UserName { get; set; }

        [DataType(DataType.Password)]
        [Required(AllowEmptyStrings = false, ErrorMessage = "Password is required")]
        [MinLength(6, ErrorMessage = "Minimum 6 characters required")]
        public string Password { get; set; }

        [DataType(DataType.Password)]
        [DisplayName("Confirm Password")]
        [Compare("Password")]
        public string ConfirmPassword { get; set; }

        public Nullable<int> IsStatus { get; set; }
        public string LoginErrorMessage { get; set; }
        }
    }

Error is: