This C# keyword is used in threading. It restricts code from being executed by more than one thread at the same time. This makes threaded programs reliable.
The lock statement uses a special syntax form to restrict concurrent access. Lock is compiled into a lower-level implementation based on threading primitives.
The Main
method creates 10 new threads, and then calls Start on each one. Please examine method "A" to see the lock statement.
using System; using System.Threading; class Program { static readonly object _object = new object(); static void A() { // Method A: lock on the readonly object. // ... Inside the lock, sleep for 100 milliseconds. // ... This is thread serialization. lock (_object) { Thread.Sleep(100); Console.WriteLine(Environment.TickCount); } } static void Main() { // Create 10 new threads. for (int i = 0; i < 10; i++) { ThreadStart start = new ThreadStart(A); new Thread(start).Start(); } } }28106840 28106949 28107043 28107136 28107246 28107339 28107448 28107542 28107636 28107745
Let's examine the intermediate representation for the lock statement. In compiler theory, high-level source texts are translated to lower-level streams of instructions.
static
methods Monitor.Enter
and Monitor.Exit
.try-finally
construct. This uses the exception handling control flow..method private hidebysig static void A() cil managed { .maxstack 2 .locals init ( [0] object obj2) L_0000: ldsfld object Program::_object L_0005: dup L_0006: stloc.0 L_0007: call void [mscorlib]System.Threading.Monitor::Enter(object) L_000c: ldc.i4.s 100 L_000e: call void [mscorlib]System.Threading.Thread::Sleep(int32) L_0013: call int32 [mscorlib]System.Environment::get_TickCount() L_0018: call void [mscorlib]System.Console::WriteLine(int32) L_001d: leave.s L_0026 L_001f: ldloc.0 L_0020: call void [mscorlib]System.Threading.Monitor::Exit(object) L_0025: endfinally L_0026: ret .try L_000c to L_001f finally handler L_001f to L_0026 }
Lock is a synchronization construct. We looked at an example and stepped into the IL. This keyword is helpful for threaded programs.