C#

public class City
{
        public int Id { get; set; }        
        public string CityName { get; set; }
        public virtual List<Zone> Zones { get; set; } = new List<Zone>();
}

public class Zone
 {
        public int Id { get; set; }
        public string ZoneName { get; set; }

        public int CityId { get; set; }
        public virtual City City { get; set; }
}

public class SettingsModel
    {
        public City NewCity { get; set; }
        public List<City> CurrentCities { get; set; }
    }

<form method="post" action="/Administration/UpdateCity">
...
<input type="hidden" id="CurrentCities_0__Id" name="CurrentCities[0].Id" value="7">
<input type="text"  id="CurrentCities_0__CityName" name="CurrentCities[0].CityName" value="Austin">
...
</form>
...
<form method="post" action="/Administration/UpdateCity">
...
<input type="hidden" id="CurrentCities_1__Id" name="CurrentCities[1].Id" value="4">
<input type="text"  id="CurrentCities_1__CityName" name="CurrentCities[1].CityName" value="Dallas">
...
</form>

public IActionResult UpdateCity([Bind(Prefix = "CurrentCities")]List<City> myCity) 
{
...
}

<input type="text" id="CurrentCities_0__Zones_0__ZoneName" name="CurrentCities[0].Zones[0].ZoneName" value="Austin Metro Area">
...
<input type="text" id="CurrentCities_1__Zones_0__ZoneName" name="CurrentCities[1].Zones[0].ZoneName" value="San Antonio Metro Area">

Chapter 1 - Events
-alert or disservices
-significant activities

Chapter 2 – Safety
-near miss
-security checks

Chapter 3 – Training
-environment
-upkeep

DROP TABLE IF EXISTS `chapters`;
CREATE TABLE `chapters` (
  `chapter` longtext CHARACTER SET utf8 COLLATE utf8_general_ci,
  `subheading` longtext CHARACTER SET utf8 COLLATE utf8_general_ci,
  `contents` longtext CHARACTER SET utf8 COLLATE utf8_general_ci,
  `sID` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`sID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

public const double NaN = (double)0.0 / (double)0.0;

0 / 0

public class IBase<T> where T:IBase<T>{

     public void Foo(T arg){
     }

     void Bar(){
         Foo(this); //<-- argument 1 cannot convert from  IBase<T> to T
     }
 }

 public class Deriv:IBase<Deriv>{
     void Bar2(){
         this.Foo(this); // <--- here is OK, no errors
     }
 }