Into what construct does the lock operator in C# transform?

The lock operator in C# is transformed into calls to Monitor.Enter and Monitor.Exit methods (or Monitor.TryEnter followed by Monitor.Exit) within a try...finally block.

// Original code with lock
object lockObject = new object();
lock (lockObject)
{
    // Protected code
}

// The transformation roughly performs the following:
object lockObject = new object();
bool lockTaken = false; // Flag to track successful monitor acquisition
try
{
    Monitor.Enter(lockObject, ref lockTaken); // Attempt to acquire the monitor
    // `Monitor.TryEnter` can be used instead of `Monitor.Enter`
    if (lockTaken) // Check if the monitor was acquired
    {
        // Protected code
    }
}
finally
{
    if (lockTaken) // Release the monitor only if it was acquired
    {
        Monitor.Exit(lockObject);
    }
}

Using Monitor.Enter with the ref bool lockTaken parameter and a try...finally block guarantees that the monitor will be released even if an exception occurs in the protected code.