Simpler Lock Usage in C#

I saw a Tweet yesterday complaining about the need to create an empty object to use as the parameter in a lock statement. They wanted this to be simplified.

It struck me that constant strings with the same content all reference the same object as the strings are interned. Thus you could just lock on a constant string without having to create an object. Thus you could do something like the code below. Of course, typos could cause you no end of pain.

Just to be clear, this is not intended to be a 'best practice'. Magic strings and the potential of multiple code sections inadvertently sharing the same string (lock object) far outweigh any benefits this pattern might add. However, it was an interesting observation of one feature of the C# compiler/runtime.

// See https://aka.ms/new-console-template for more information
 
Console.WriteLine($"The strings are the same object {ReferenceEquals("A String", "A String")}");
 
var taskList = new List<Task>();
for (var i = 0; i < 10; i++)
{
    taskList.Add(RunTask1(i));
    taskList.Add(RunTask2(i));
}
 
Task.WaitAll(taskList.ToArray());
 
Console.WriteLine("Done");
 
async Task RunTask1(int i)
{
    await Task.Delay(1);
 
    lock ("A String")
    {
        Console.WriteLine($"Entering task1-{i} lock");
        Thread.Sleep(500);
        Console.WriteLine($"Exiting task1-{i} lock");
    }
}
 
 
async Task RunTask2(int i)
{
    await Task.Delay(200);
    lock ("A String")
    {
        Console.WriteLine($"Entering task2-{i} lock");
        Thread.Sleep(300);
        Console.WriteLine($"Exiting task2-{i} lock");
    }
}

The strings are the same object True
Entering task1-0 lock
Exiting task1-0 lock
Entering task1-1 lock
Exiting task1-1 lock
Entering task1-3 lock
Exiting task1-3 lock
Entering task1-2 lock
Exiting task1-2 lock
Entering task1-5 lock
Exiting task1-5 lock
Entering task1-9 lock
Exiting task1-9 lock
Entering task2-7 lock
Exiting task2-7 lock
Entering task2-9 lock
Exiting task2-9 lock
Entering task2-6 lock
Exiting task2-6 lock
Entering task2-5 lock
Exiting task2-5 lock
Entering task2-3 lock
Exiting task2-3 lock
Entering task1-4 lock
Exiting task1-4 lock
Entering task1-8 lock
Exiting task1-8 lock
Entering task1-7 lock
Exiting task1-7 lock
Entering task1-6 lock
Exiting task1-6 lock
Entering task2-8 lock
Exiting task2-8 lock
Entering task2-4 lock
Exiting task2-4 lock
Entering task2-2 lock
Exiting task2-2 lock
Entering task2-1 lock
Exiting task2-1 lock
Entering task2-0 lock
Exiting task2-0 lock
Done   

History

• 10^th December, 2022: Initial version