What is the difference between task and thread

Question

In C  4 0  we have Task in the System Threading Tasks namespace  What is the true difference between Thread and Task  I did some sample program help taken from MSDN   for my own sake of learning with   Parallel Invoke  Parallel For  Parallel ForEach    but have many doubts as the idea is not so clear    I have initially searched in Stackoverflow for a similar type of question but may be with this question title I was not able to get the same  If anyone knows about the same type of question being posted here earlier  kindly give the reference of the link

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You can use Task to specify what you want to do then attach that Task with a Thread  so that Task would be executed in that newly made Thread rather than on the GUI thread   Use Task with the TaskFactory StartNew Action action   In here you execute a delegate so if you didn t use any thread it would be executed in the same thread  GUI thread   If you mention a thread you can execute this Task in a different thread  This is an unnecessary work cause you can directly execute the delegate or attach that delegate to a thread and execute that delegate in that thread  So don t use it  it s just unnecessary  If you intend to optimize your software this is a good candidate to be removed      Please note that the Action is a delegate

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I usually use Task to interact with Winforms and simple background worker to make it not freezing the UI  here an example when I prefer using Task  private async void buttonDownload Click object sender  EventArgs e        buttonDownload Enabled   false      await Task Run      gt            using  var client   new WebClient                          client DownloadFile  http   example com file mpeg    file mpeg                         buttonDownload Enabled   true      VS  private void buttonDownload Click object sender  EventArgs e        buttonDownload Enabled   false      Thread t   new Thread      gt                using  var client   new WebClient                          client DownloadFile  http   example com file mpeg    file mpeg                      this Invoke  MethodInvoker delegate                         buttonDownload Enabled   true                          t IsBackground   true      t Start        the difference is you don t need to use MethodInvoker and shorter code

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A Task can be seen as a convenient and easy way to execute something asynchronously and in parallel    Normally a Task is all you need  I cannot remember if I have ever used a thread for something else than experimentation   You can accomplish the same with a thread  with lots of effort  as you can with a task   Thread  int result   0  Thread thread   new System Threading Thread      gt         result   1       thread Start    thread Join    Console WriteLine result     is 1   Task  int result   await Task Run      gt        return 1       Console WriteLine result     is 1   A task will by default use the Threadpool  which saves resources as creating threads can be expensive  You can see a Task as a higher level abstraction upon threads   As this article points out  task provides following powerful features over thread    Tasks are tuned for leveraging multicores processors  If system has multiple tasks then it make use of the CLR thread pool internally  and so do not have the overhead associated with creating a dedicated thread using the Thread  Also reduce the context switching time among multiple threads     Task can return a result There is no direct mechanism to return the result from thread    Wait on a set of tasks  without a signaling construct   We can chain tasks together to execute one after the other     Establish a parent child relationship when one task is started from another task     Child task exception can propagate to parent task     Task support cancellation through the use of cancellation tokens   Asynchronous implementation is easy in task  using    async    and    await    keywords

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Task is like a operation that you wanna perform   Thread helps to manage those operation through multiple process nodes  task is a lightweight option as Threading can lead to a complex code management I will suggest to read from MSDN Best in world  always  Task  Thread

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In addition to above points  it would be good to know that    A task is by default a background task  You cannot have a foreground task  On the other hand a thread can be background or foreground  Use IsBackground property to change the behavior   Tasks created in thread pool recycle the threads which helps save resources  So in most cases tasks should be your default choice  If the operations are quick  it is much better to use a task instead of thread  For long running operations  tasks do not provide much advantages over threads

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Thread  The bare metal thing  you probably don t need to use it  you probably can use a LongRunning task and take the benefits from the TPL - Task Parallel Library  included in  NET Framework 4  february  2002  and above  also  NET Core    Tasks  Abstraction above the Threads  It uses the thread pool  unless you specify the task as a LongRunning operation  if so  a new thread is created under the hood for you    Thread Pool  As the name suggests  a pool of threads  Is the  NET framework handling a limited number of threads for you  Why  Because opening 100 threads to execute expensive CPU operations on a Processor with just 8 cores definitely is not a good idea  The framework will maintain this pool for you  reusing the threads  not creating killing them at each operation   and executing some of them in parallel  in a way that your CPU will not burn   OK  but when to use each one   In resume  always use tasks   Task is an abstraction  so it is a lot easier to use  I advise you to always try to use tasks and if you face some problem that makes you need to handle a thread by yourself  probably 1  of the time  then use threads    BUT be aware that    I O Bound  For I O bound operations  database calls  read write files  APIs calls  etc  avoid using normal tasks  use LongRunning tasks  or threads if you need to   Because using tasks would lead you to a thread pool with a few threads busy and a lot of another tasks waiting for its turn to take the pool   CPU Bound  For CPU bound operations just use the normal tasks  that internally will use the thread pool  and be happy

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In computer science terms  a Task is a future or a promise   Some people use those two terms synonymously  some use them differently  nobody can agree on a precise definition   Basically  a Task lt T gt   quot promises quot  to return you a T  but not right now honey  I m kinda busy  why don t you come back later  A Thread is a way of fulfilling that promise  But not every Task needs a brand-new Thread   In fact  creating a thread is often undesirable  because doing so is much more expensive than re-using an existing thread from the thread pool  More on that in a moment   If the value you are waiting for comes from the filesystem or a database or the network  then there is no need for a thread to sit around and wait for the data when it can be servicing other requests  Instead  the Task might register a callback to receive the value s  when they re ready  In particular  the Task does not say why it is that it takes such a long time to return the value  It might be that it takes a long time to compute  or it might that it takes a long time to fetch  Only in the former case would you use a Thread to run a Task   In  NET  threads are freaking expensive  so you generally want to avoid them as much as possible and really only use them if you want to run multiple heavy computations on multiple CPUs  For example  in Windows  a thread weighs 12 KiByte  I think   in Linux  a thread weighs as little as 4 KiByte  in Erlang BEAM even just 400 Byte  In  NET  it s 1 MiByte

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A task is something you want done   A thread is one of the many possible workers which performs that task   In  NET 4 0 terms  a Task represents an asynchronous operation  Thread s  are used to complete that operation by breaking the work up into chunks and assigning to separate threads

[c#] What is the difference between task and thread?

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