Question

I’m working on a project where I have to store data in a WCF service but I’m unsure how I can maintain the changes when the data is manipulated.

[ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Single, InstanceContextMode =
InstanceContextMode.Single,UseSynchronizationContext = true)]
public class TestService : ITestService {
    private List<TestClass> cl;

    public TestService()
    {
        cl = new List<TestClass>();
        TestClass tc = new TestClass(5);
        cl.add(tc);
    }

    public void Diminish(int x)
    {
         cl[0].Value -= x;
    }

    public TestClass ReturnValue(int p)
    {
        return cl[p];
    }
}

So now when a client uses this service how can I send an updated value of the collection cl?

Answer 1

You could use a static field. But obviously once you do that you need to synchronize the access to it because the List<T> class is not thread safe:

public class TestService : ITestService {
    private static List<TestClass> cl;
    private static object _syncRoot = new object();

    static TestService()
    {
        cl = new List<TestClass>();
        TestClass tc = new TestClass(5);
        cl.Add(tc);
    }

    public void Diminish(int x)
    {
         lock (_syncRoot)
         {
             cl[0].Value -= x;
         }
    }

    public TestClass ReturnValue(int p)
    {
        lock (_syncRoot)
        {
            return cl[p];
        }
    }
}

or you could also use the SynchronizedCollection<T> class which is thread safe:

public class TestService
{
    private static SynchronizedCollection<TestClass> cl;

    static TestService()
    {
        cl = new SynchronizedCollection<TestClass>();
        TestClass tc = new TestClass(5);
        cl.Add(tc);
    }

    public void Diminish(int x)
    {
        cl[0].Value -= x;
    }

    public TestClass ReturnValue(int p)
    {
        return cl[p];
    }
}