lock C# with Example

lock provides thread-safety for a block of code, so that it can be accessed by only one thread within the same 
process. Example: 
private static object _lockObj = new object(); 
static void Main(string[] args) 
{ 
Task.Run(() => TaskWork()); 
Task.Run(() => TaskWork()); 
Task.Run(() => TaskWork()); 
Console.ReadKey(); 
} 
private static void TaskWork() 
{ 
lock(_lockObj) 
{ 
Console.WriteLine("Entered"); 
Task.Delay(3000); 
Console.WriteLine("Done Delaying"); 
// Access shared resources safely 
Console.WriteLine("Leaving"); 
} 
} 
Output: 
Entered 
Done Delaying 
Leaving 
Entered 
Done Delaying 
Leaving 
Entered 
Done Delaying 
Leaving 
Use cases: 
Whenever you have a block of code that might produce side-effects if executed by multiple threads at the same 
time. The lock keyword along with a shared synchronization object (_objLock in the example) can be used to 
prevent that. 
Note that _objLock can't be null and multiple threads executing the code must use the same object instance 
(either by making it a static field, or by using the same class instance for both threads) 
From the compiler side, the lock keyword is a syntactic sugar that is replaced by Monitor.Enter(_lockObj); and 
 

Monitor.Exit(_lockObj);. So if you replace the lock by surrounding the block of code with these two methods, 
you would get the same results. You can see actual code in Syntactic sugar in C# - lock example