How to call any method asynchronously in c

Question

Could someone please show me a small snippet of code which demonstrates how to call a method asynchronously in c

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Here s a way to do it      The method to call void Foo         Action action   Foo  action BeginInvoke ar   gt  action EndInvoke ar   null     Of course you need to replace Action by another type of delegate if the method has a different signature

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If you use action BeginInvoke    you have to call EndInvoke somewhere - else the framework has to hold the result of the async call on the heap  resulting in a memory leak   If you don t want to jump to C  5 with the async await keywords  you can just use the Task Parallels library in  Net 4   It s much  much nicer than using BeginInvoke EndInvoke  and gives a clean way to fire-and-forget for async jobs   using System Threading Tasks      void Foo         new Task Foo  Start      If you have methods to call that take parameters  you can use a lambda to simplify the call without having to create delegates   void Foo2 int x  string y        return        new Task      gt    Foo2 42   life  the universe  and everything      Start      I m pretty sure  but admittedly not positive  that the C  5 async await syntax is just syntactic sugar around the Task library

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Check out the MSDN article Asynchronous Programming with Async and Await if you can afford to play with new stuff  It was added to  NET 4 5   Example code snippet from the link  which is itself from this MSDN sample code project       Three things to note in the signature       - The method has an async modifier        - The return type is Task or Task lt T gt    See  Return Types  section         Here  it is Task lt int gt  because the return statement returns an integer       - The method name ends in  Async   async Task lt int gt  AccessTheWebAsync             You need to add a reference to System Net Http to declare client      HttpClient client   new HttpClient            GetStringAsync returns a Task lt string gt   That means that when you await the         task you ll get a string  urlContents       Task lt string gt  getStringTask   client GetStringAsync  http   msdn microsoft com            You can do work here that doesn t rely on the string from GetStringAsync      DoIndependentWork            The await operator suspends AccessTheWebAsync           - AccessTheWebAsync can t continue until getStringTask is complete           - Meanwhile  control returns to the caller of AccessTheWebAsync           - Control resumes here when getStringTask is complete            - The await operator then retrieves the string result from getStringTask       string urlContents   await getStringTask          The return statement specifies an integer result          Any methods that are awaiting AccessTheWebAsync retrieve the length value       return urlContents Length      Quoting      If AccessTheWebAsync doesn t have any work that it can do between calling GetStringAsync and awaiting its completion  you can simplify your code by calling and awaiting in the following single statement    string urlContents   await client GetStringAsync      More details are in the link

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Starting with  Net 4 5 you can use Task Run to simply start an action   void Foo string args        Task Run      gt  Foo  bar       Task Run vs Task Factory StartNew

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public partial class MainForm   Form       Image img      private void button1 Click object sender  EventArgs e                LoadImageAsynchronously  http   media1 santabanta com full5 Indian 20 20Celebrities F  Jacqueline 20Fernandez jacqueline-fernandez-18a jpg               private void LoadImageAsynchronously string url                           This is a classic example of how make a synchronous code snippet work asynchronously          A class implements a method synchronously like the WebClient s DownloadData      function for example              1  First wrap the method call in an Anonymous delegate               2  Use BeginInvoke      and send the wrapped anonymous delegate object as the last parameter along with a callback function name as the first parameter               3  In the callback method retrieve the ar s AsyncState as a Type  typecast  of the anonymous delegate  Along with this object comes EndInvoke      as free Gift              4  Use EndInvoke      to retrieve the synchronous call   s return value in our case it will be the WebClient s DownloadData        s return value                     try                       Func lt Image gt  load image Async   delegate                                 WebClient wc   new WebClient                    Bitmap bmpLocal   new Bitmap new MemoryStream wc DownloadData url                     wc Dispose                    return bmpLocal                              Action lt IAsyncResult gt  load Image call back   delegate IAsyncResult ar                                Func lt Image gt  ss    Func lt Image gt  ar AsyncState                  Bitmap myBmp    Bitmap ss EndInvoke ar                    if  img    null  img Dispose                    if  myBmp    null                      img   myBmp                  Invalidate                      timer Enabled   true                               load image Async BeginInvoke callback load Image  load image Async                            load image Async BeginInvoke new AsyncCallback load Image call back   load image Async                                  catch  Exception ex                                 protected override void OnPaint PaintEventArgs e                if  img    null                        Graphics grfx   e Graphics              grfx DrawImage img new Point 0 0

[c#] How to call any method asynchronously in c#

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