Question

I have a WCF service that I am calling from multiple clients. I need to store and manage a value globally. On my service I have the following attributes:

[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Single)]

In my service I have something similar to this:

private static int counter;

public void PrintCounter()
{
    counter++;
    StreamWriter sw = new StreamWriter(@"C:\outFile.txt", true);
    sw.WriteLine("Counter: " + counter);
    sw.Close();
}

With my limited knowledge of WCF, I would presume that I have a Singleton service and the fact that my private variable is static, that all calls to the service would use the same object.

However, when I look at my log output, I see the following:

Counter: 1
Counter: 1

What I expected to see would be:

Counter: 1
Counter: 2

Am I missing something to make this work the way I need it to? Do I need to store objects in some sort of cache? Any help is greatly appreciated.

I can post more coded if needed.

Answer 1

Since it’s a singleton service, e.g. only one instance will ever exists of it, why don’t you make this a regular class member variable??

Since the ConcurrencyMode is set to single, too – you don’t even have to worry about concurrent access to the variable.

On the other hand – singleton with ConcurrencyMode=Single is a recipe for a really really slow service which might become a bottleneck quickly – so you might want to program your code in such a way that it would also work under ConcurrencyMode=Multiple with potentially concurrent access to the member variable.