Question

I am trying to reproduce a threading error condition within an HTTP Handler.

Basically, the ASP.net worker procecss is creating 2 threads which invoke the HTTP handler in my application simultaneously when a certain page loads.

Inside the http handler, is a resource which is not thread safe. Hence, when the 2 threads try to access it simultaneously an exception occurs.

I could potentially, put a lock statement around the resource, however I want to make sure that it is infact the case. So I wanted to create the situation in a console application first.

But i cant get 2 threads to execute a method at the same time like asp.net wp does. So, my question is how can you can create 2 threads which can execute a method at the same time.

Edit:

The underlying resource is a sql database with a user table (has a name column only). Here is a sample code i tried.

[TestClass]
    public class UnitTest1
    {
        [TestMethod]
        public void Linq2SqlThreadSafetyTest()
        {
            var threadOne = new Thread(new ParameterizedThreadStart(InsertData));
            var threadTwo = new Thread(new ParameterizedThreadStart(InsertData));

            threadOne.Start(1); // Was trying to sync them via this parameter.
            threadTwo.Start(0);

            threadOne.Join();
            threadTwo.Join();
        }


        private static void InsertData( object milliseconds )
        {
            // Linq 2 sql data context
            var database = new DataClassesDataContext();

            // Database entity
            var newUser = new User {Name = "Test"};

            database.Users.InsertOnSubmit(newUser);

            Thread.Sleep( (int) milliseconds);

            try
            {
                database.SubmitChanges(); // This statement throws exception in the HTTP Handler.
            }

            catch (Exception exception)
            {
                Debug.WriteLine(exception.Message);
            }
        }
    }

Answer 1

You could just set a static time to start your work like this.

private static DateTime startTime = DateTime.Now.AddSeconds(5); //arbitrary start time

static void Main(string[] args)
{
    ThreadStart threadStart1 = new ThreadStart(DoSomething);
    ThreadStart threadStart2 = new ThreadStart(DoSomething);
    Thread th1 = new Thread(threadStart1);
    Thread th2 = new Thread(threadStart2);

    th1.Start();             
    th2.Start();

    th1.Join();
    th2.Join();

    Console.ReadLine();
}

private static void DoSomething()
{
    while (DateTime.Now < startTime)
    {
        //do nothing
    }

    //both threads will execute code here concurrently
}