When to use Task Delay when to use Thread Sleep

Question

Are there good rule s  for when to use Task Delay versus Thread Sleep   Specifically  is there a minimum value to provide for one to be effective efficient over the other  Lastly  since Task Delay causes context-switching on a async await state machine  is there an overhead of using it

User · Answer

I want to add something  Actually  Task Delay is a timer based wait mechanism  If you look at the source you would find a reference to a Timer class which is responsible for the delay  On the other hand Thread Sleep actually makes current thread to sleep  that way you are just blocking and wasting one thread  In async programming model you should always use Task Delay   if you want something continuation  happen after some delay

User · Answer

My opinion  Task Delay   is asynchronous  It doesn t block the current thread  You can still do other operations within current thread  It returns a Task return type  Thread Sleep   doesn t return anything    You can check if this task is completed use Task IsCompleted property  later after another time-consuming process  Thread Sleep   doesn t have a return type  It s synchronous  In the thread  you can t really do anything other than waiting for the delay to finish  As for real-life usage  I have been programming for 15 years  I have never used Thread Sleep   in production code  I couldn t find any use case for it  Maybe that s because I mostly do web application development

User · Answer

The biggest difference between Task Delay and Thread Sleep is that Task Delay is intended to run asynchronously  It does not make sense to use Task Delay in synchronous code  It is a VERY bad idea to use Thread Sleep in asynchronous code   Normally you will call Task Delay    with the await keyword   await Task Delay 5000     or  if you want to run some code before the delay   var sw   new Stopwatch    sw Start    Task delay   Task Delay 5000   Console WriteLine  async  Running for  0  seconds   sw Elapsed TotalSeconds   await delay    Guess what this will print  Running for 0 0070048 seconds  If we move the await delay above the Console WriteLine instead  it will print Running for 5 0020168 seconds   Let s look at the difference with Thread Sleep   class Program       static void Main string   args                Task delay   asyncTask            syncCode            delay Wait            Console ReadLine               static async Task asyncTask                 var sw   new Stopwatch            sw Start            Console WriteLine  async  Starting            Task delay   Task Delay 5000           Console WriteLine  async  Running for  0  seconds   sw Elapsed TotalSeconds           await delay          Console WriteLine  async  Running for  0  seconds   sw Elapsed TotalSeconds           Console WriteLine  async  Done               static void syncCode                 var sw   new Stopwatch            sw Start            Console WriteLine  sync  Starting            Thread Sleep 5000           Console WriteLine  sync  Running for  0  seconds   sw Elapsed TotalSeconds           Console WriteLine  sync  Done              Try to predict what this will print        async  Starting   async  Running for 0 0070048 seconds   sync  Starting   async  Running for 5 0119008 seconds   async  Done   sync  Running for 5 0020168 seconds   sync  Done     Also  it is interesting to notice that Thread Sleep is far more accurate  ms accuracy is not really a problem  while Task Delay can take 15-30ms minimal  The overhead on both functions is minimal compared to the ms accuracy they have  use Stopwatch Class if you need something more accurate   Thread Sleep still ties up your Thread  Task Delay release it to do other work while you wait

User · Answer

if the current thread is killed and you use Thread Sleep and it is executing then you might get a ThreadAbortException   With Task Delay you can always provide a cancellation token and gracefully kill it  Thats one reason I would choose Task Delay  see http   social technet microsoft com wiki contents articles 21177 visual-c-thread-sleep-vs-task-delay aspx  I also agree efficiency is not paramount in this case

User · Answer

Use Thread Sleep when you want to block the current thread   Use Task Delay when you want a logical delay without blocking the current thread   Efficiency should not be a paramount concern with these methods  Their primary real-world use is as retry timers for I O operations  which are on the order of seconds rather than milliseconds

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