//Here Is my code below I am using Remote validation

  public ActionResult Settings()
        {
            return View();
        }

        //For checking New Password Doesnt match With Old Password
        public JsonResult IsValidUsername(string newPassword)
        {
            AdminRepository service = new AdminRepository();
            return Json(service.IsValidUsername(newPassword), JsonRequestBehavior.AllowGet);
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public ActionResult Settings(AdminViewModels model, FormCollection collection)
        {
            try
            {
                ModelState.Remove("EmailID");
                ModelState.Remove("IsValid");


                if (ModelState.IsValid)
                {
                    AdminViewModels adminObj = (AdminViewModels)Session["Admin"];
                    model.AdminID = adminObj.AdminID;
                    string newPassword = collection["NewPassword"];
                    if (!string.IsNullOrEmpty(newPassword))
                    {
                        bool exists = admin.PasswordUpdate(model, newPassword);
                        if (exists)
                            ViewBag.message = "Password Updated Successfully";
                        else
                            ViewBag.messageinvalid = "Invalid Password";
                    }
                    else
                    {
                        ViewBag.nullmessage = "Enter New Password";
                    }
                }

                return View();
            }
            catch (Exception ex)
            {
                return View("Error", new HandleErrorInfo(ex, "model", "collection"));
            }

        }

public bool IsValidUsername(string newpassword)
        {
            using (dbHealthSplashEntities dbcontext = new dbHealthSplashEntities())
            {
                return !dbcontext.Admins.Any(user => user.Password == newpassword);
            }
        }

public class AdminViewModels:IValidatableObject
    {
        public int AdminID { get; set; }

        [Required(ErrorMessage = "EmailID is required")]
        [StringLength(16, ErrorMessage = "Must be between 5 and 50 characters", MinimumLength = 5)]
        [RegularExpression("^[a-zA-Z0-9_\.-]+@([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,6}$", ErrorMessage = "E-mail is not valid")]
        [EmailAnnotation]
        public string EmailID { get; set; }

        [Required(ErrorMessage = "Password is required")]
        //[StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
        [DataType(DataType.Password)]
        [Display(Name = "Password")]
        public string Password { get; set; }


        [Required(ErrorMessage = "Enter New Password")]
        //[StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 6)]
        [DataType(DataType.Password)]
        [Display(Name = "newPassword")]
        [Remote("IsValidUsername", "Admin", ErrorMessage = "It Seems You Have Entered Same Password As Old Password!!!")]
        public string newPassword { get; set; }

        [Required]
        [System.ComponentModel.DataAnnotations.Compare("newPassword", ErrorMessage = "The password and confirmation password do not match.")]
        public string ConfirmPassword { get; set; }
        public Nullable<bool> Flag { get; set; }

        public bool RememberMe { get; set; }

        public bool IsValid { get; set; }


        public IEnumerable<ValidationResult> Validate(ValidationContext context)
        {
            if (newPassword == Password)
                yield return new ValidationResult("Passwords should not be the same");
        }
    }