How does this work?

Question

Hi

I might be missing something extremely obvious here but given the following:-

Public Lazy(bool isThreadSafe)

The write up for this is

true to make this instance usable concurrently by multiple threads; false to make the instance usable by only one thread at a time.

I cannot see any logic to determine what would happen if true was set or if false was set?

Regards

Steven

Vulpes · Answer

Yes the Lazy constructor which takes a bool parameter will contain some logic which checks the argument passed in and then constructs an instance of T using its default constructor in either a threadsafe (true) or non-threadsafe (false) manner. When you have a generic class such as Lazy the constructor is declared as if it were non-generic except that its parameters (and body) can make use of the type parameter for the class as a whole. For example this constructor overload makes use of T in the first parameter: public Lazy(Func valueFactory bool isThreadSafe)

S · Answer

Thanks Vulpes When you say internal to the constructor are you implying that the constructor would have some conditional logic to determine the correct Enum to use depending whether true or false. When it comes to usage of Lazy how does this fit with invoking the underlining constructor Public Lazy() is it the same as invoking a non type parameter constructor? Regards Steven

Vulpes · Answer

The logic is internal to the Lazy constructor. According to the MSDN docs if it's passed a value of true then its thread safety mode is: LazyThreadSafetyMode.ExecutionAndPublication but if it's passed a value of false then its thread safety mode is: LazyThreadSafetyMode.None For what these values mean I'd check out: http://msdn.microsoft.com/en-us/library/system.threading.lazythreadsafetymode.aspx Of course it's up to you to pass the appropriate argument to the constructor depending on whether you need it to be thread-safe when accessed by multiple threads or not.