public void TestWithoutParaller()
{
var a = LockSingleton.getInstance();
var b = LockSingleton.getInstance();
Assert.IsTrue(object.ReferenceEquals(a, b));
}
public void GetInstancesWithParaller()
{
Parallel.For(0, 100000, task =>
{
LockSingleton.getInstance();
});
Assert.AreEqual(1, LockSingleton.counter);
}
public void TestLockSingletonWithParaller()
{
LockSingleton a = null;
LockSingleton b = null;
LockSingleton c = null;
Parallel.Invoke(
() => { c = LockSingleton.getInstance(); },
() => { b = LockSingleton.getInstance(); },
() => { a = LockSingleton.getInstance(); },
() => { c = LockSingleton.getInstance(); },
() => { c = LockSingleton.getInstance(); }
);
Assert.IsTrue(object.ReferenceEquals(a, b));
Assert.AreEqual(1, LockSingleton.counter);
}
/// <summary>
/// 双重锁定Sigleton
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void btn_DoubLockSigleton_Click(object sender, System.EventArgs e)
{
LockSingleton s1 = LockSingleton.Instance;
LockSingleton s2 = LockSingleton.Instance;
string strResult = "";
if (s1.Equals(s2))
{
strResult = "[LockSingleton]the same instance";
}
else
{
strResult = "[LockSingleton]the defferent instance";
}
UpdateResult(strResult);
}
public void ShouldTheSingletonDesignPatternUsingLockCreatingASingleInstance()
{
LockSingleton firstInstance = null;
LockSingleton SecondInstance = null;
Parallel.Invoke(
() => firstInstance = LockSingleton.Instance,
() => SecondInstance = LockSingleton.Instance);
firstInstance.Should().Be(SecondInstance);
LockSingleton.Counter.Should().Be(1);
// The point that you need to remember is Lock is the best option to handle the singleton instance
// Using locks we can synchronize the method. So that only one thread can access it at any given point of time.
// We lock the shared resource and then checks whether the instance is created or not.
// If the instance is already created then we simply return that instance else we will create the instance and then return that instance.
// IMPORTANT:
// The implementation using lock solves the multithreading issue. But the problem is that it is slow down your application as only one
// thread can access the Instance property at any given point of time. We can overcome this problem by using the Double-checked locking mechanism.
}
