Client updates its object on getting callback from the server
//ATC_Slaves.cs, on client side
namespace ATCslave
{
[CallbackBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, UseSynchronizationContext = false)]
public class ATC_Slaves :Iservercallback
{
static Airport a;
static List<Airplane> b = new List<Airplane>();
static List<AirRoute> c = new List<AirRoute>();
public ATC_Slaves(Airport d, List<Airplane> e,List<AirRoute> f)
{
a = d;
b = e;
c = f;
}
public ATC_Slaves()
{
}
public void do_update()
{
System.Console.Write(a.AirportID + a.AirportName);
System.Console.ReadLine();
//check which flight need to takeoff, increase time duration of every flight, and make sure the air route list is also changed
//check which flight have to land, check on the basis of fuel left.
//check the outbound flights , update its fuel if the flight is very close to the destination airport hand it over to the next airport
}
}
}
The Service object of the Master server
//Pogram.cs,, on client side
using Master;
using System;
using System.Collections.Generic;
using System.Linq;
using System.ServiceModel;
using System.Text;
using System.Threading.Tasks;
namespace ATCslave
{
[CallbackBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, UseSynchronizationContext = false)]
public class ATC_Slaves :Iservercallback
{
static Airport a;
static List<Airplane> b = new List<Airplane>();
static List<AirRoute> c = new List<AirRoute>();
public ATC_Slaves(Airport d, List<Airplane> e,List<AirRoute> f)
{
a = d;
b = e;
c = f;
}
public ATC_Slaves()
{
}
public void do_update()
{
System.Console.Write(a.AirportID + a.AirportName);
System.Console.ReadLine();
//check which flight need to takeoff, increase time duration of every flight, and make sure the air route list is also changed
//check which flight have to land, check on the basis of fuel left.
//check the outbound flights , update its fuel if the flight is very close to the destination airport hand it over to the next airport
}
}
}
// on server IMaster.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.ServiceModel;
using System.Text;
using System.Threading.Tasks;
namespace Master
{
//callback interface
[ServiceContract]
public interface Iservercallback
{
[OperationContract(IsOneWay=true)]
void do_update();
}
[ServiceContract(CallbackContract=typeof(Iservercallback))]
public interface IMaster
{
[OperationContract]
Airplane get_airplane(int id);
[OperationContract]
AirRoute get_airroute(int id);
[OperationContract]
Airport addslave();
[OperationContract]
void do_long_work();
}
}
// On server side,, MasterImpl.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.ServiceModel;
using System.Text;
using System.Threading.Tasks;
namespace Master
{
[ServiceBehavior(ConcurrencyMode=ConcurrencyMode.Multiple,UseSynchronizationContext=false, InstanceContextMode=InstanceContextMode.Single)]
class MasterImpl :IMaster
{
int i = 1;
public List<Iservercallback> list_of_slaves=new List<Iservercallback>();
public Airplane get_airplane(int id)
{
Airplane air_p = new Airplane(i);
return air_p;
}
public AirRoute get_airroute(int id)
{
AirRoute air_route = new AirRoute(id);
return air_route;
}
public Airport addslave()
{
// get a reference to the client side callback object
Iservercallback cb= OperationContext.Current.GetCallbackChannel<Iservercallback>();
list_of_slaves.Add(cb);
System.Console.WriteLine("hey**");
Airport a1 = new Airport(i);
i++;
return a1;
}
public void do_long_work()
{
list_of_slaves[0].do_update();
}
}
}
// on server side, Program.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using ATCDatabase;
using System.ServiceModel;
//create an interface and its implementation class
namespace Master
{
class Program
{
public delegate void Binaryop();
static void Main(string[] args)
{
MasterImpl m = new MasterImpl();
ServiceHost host;
NetTcpBinding tcpBinding = new NetTcpBinding();
host = new ServiceHost(m);
host.AddServiceEndpoint(typeof(IMaster), tcpBinding,"net.tcp://localhost:8005/MasterService");
host.Open();
System.Console.WriteLine("press Enter to exit");
int ip=0;
List<Iservercallback> c = m.list_of_slaves;
while(true)
{
if(c.Count!=0)
{
if (c[ip] != null)
c[ip].do_update();
//System.Console.WriteLine(c.Count);
}
}
// block waiting for client requests
host.Close();
}
}
}
My question is when the server do callback with the list of slaves object, on the client, on the client side null reference exception occurs
System.Console.Write(a.AirportID + a.AirportName);// on this line.
I am confused why the static variables are null.
