Matevž Gačnik's Weblog

The following service will allow you to check how Indigo instancing behaviour works:

using System;
using System.ServiceModel;

[ServiceContract]
interface ICanRandom
{
 [OperationContract]
 int Randomize(int intLow, int intHigh);

 [OperationContract]
 int GetLastNumber();
}

[ServiceBehavior(InstanceMode = InstanceMode.Singleton, ConcurrencyMode = ConcurrencyMode.Multiple)]
public class RandomizerService : ICanRandom
{
 private int intLastNumber;
 private Random r = new Random(DateTime.Now.Millisecond);

 public int Randomize(int intLow, int intHigh)
 {
  System.Threading.Thread.Sleep(5000);
  int intRandomNumber = r.Next(intLow, intHigh);
  intLastNumber = intRandomNumber;
  return intRandomNumber;
 }

 public int GetLastNumber()
 {
  return intLastNumber;
 }
}

This service will return a random number for multiple clients. Try simulating it with the following client code:

using System;
using System.Threading;

class Program
{
 static void Main(string[] args)
 {
  Thread t1 = new Thread(new ParameterizedThreadStart(Program.CallService));
  Thread t2 = new Thread(new ParameterizedThreadStart(Program.CallService));
  Console.WriteLine("Threads running.");
  t1.Start(1);
  t2.Start(2);
 }

 static void CallService(object intThread)
 {
  CanRandomProxy objWS = new CanRandomProxy("ICanRandom");
  Console.WriteLine("Thread {0} - Method call.", intThread);
  Console.WriteLine("Thread {0} - Random number: {1}", intThread, objWS.Randomize(10, 110));
  Console.WriteLine("Thread {0} - Last random number: {1}", intThread, objWS.GetLastNumber());
  Console.WriteLine("Thread {0} - Done.", intThread);
 }
}

Singleton services process all requests using a single service instance. Try changing the ConcurrencyMode property of ServiceBehaviour attribute to obtain different instancing semantics. Having InstanceMode set to PerCall (current default) will disable ConcurrencyMode.Multiple behaviour, which is expected.