Do properties have volatile effect?

Question

In the code below will read1 be always equal to read2, provided property Flag can be changed from other threads? Concern here is that

Answer 1

No, the property is not volatile.

While I have not been able to obtain a satisfactory demonstration for your initial scenario, this alternative method should prove the statement nicely:

class Program
{
    public bool Flag { get; set; }

    public void VolatilityTest()
    {
        bool work = false;
        while (!Flag)
        {
            work = !work; // fake work simulation
        }
    }

    static void Main(string[] args)
    {
        Program p = new Program();
        var t = new Thread(p.VolatilityTest);
        t.Start();
        Thread.Sleep(1000);
        p.Flag = true;
        t.Join();
    }
}

Building this in Release mode will make the program deadlock, hence proving that Flag does not have volatile behavior (i.e. it gets "optimized" between reads).

Replacing public bool Flag { get; set; } with public volatile bool Flag; will make the program terminate correctly.