Styjun

BACKGROUND: I'm trying to make an async Task in my MVCcontroller class that will call a method in my modelclass which will insert a bunch of data into multiple sql tables using an already existing sql table.
As the frontend will time out when called from there if it's not async (It makes millions of operations) I wish to use this controller task to run async operations.
Once it is done with it's operations it should write to a file that I will see and understand that all computations are done.
Yes, there might be smarter ways of calling the Task but that's for later, for now I just wish to figure out how to do the async set-up.

PROBLEM/QUESTION:
Controller says that the await_part can not await void, can I just return something like Json(success)? Or how do I do this set up? I'm kind of a rookie.

In the model method I wish to look at the existing sql-table and use it to create more sql-tables that I will persist in the database, not really interested in sending anything back besides something that says "I'm done with the calculations".

Controller calling the model method that will perform actions.

 public async Task GenerateBackEndCalculations(string sqlTableName)
 
 if (nameOfTable == "sqlTableName")
 
 await _context.BackEndCalculations(); 
 

 

the model method that looks like this

public void BackEndCalculations ()
 
 Do something here, and maybe return something if I have to??? 

 

If i understand you correctly, you can change void to Task (and add async keyword) any where and as long as there is a await in your function. If you don`t have any async method to await, just return some completed Task. For example Task.CompletedTask;

public async Task BackEndCalculations ()
 
 Do something async

Or

public Task BackEndCalculations ()
 
 Do something sync
 return Task.CompletedTask;

If you want to use await in BackEndCalculations it cannot return void, it needs to return a Task.

Here are your options:

public Task BackEndCalculations() ... 
public Task<JsonObject> BackEndCalculations() ... 
public async Task BackEndCalculations() ... 
public async Task<JsonObject> BackEndCalculations() ... 

Depending on how the body of your function looks like

As the frontend will time out when called from there if it's not async (It makes millions of operations) I wish to use this controller task to run async operations.

Asynchronous code is not going to help you (see the section "Not a Silver Bullet"). In summary, async on ASP.NET is a way to yield to the server's thread pool - it is not a way to yield (or return) to the client/browser.

There are a few approaches to returning early from ASP.NET requests, but most of them are dangerous to some degree or another. Since you already have a database, I'd recommend looking at HangFire. Note that your HangFire processing should be done outside ASP.NET - e.g., in an Azure Worker Role or Win32 Service.

For making any synchronous method to behave like async, just add two things, in method signature replace void with Task. and at the end of the method write return Task.CompletedTask;.

Final implementation is like

 public Task ASimpleSynchronousMethod()
 // TO DO

 // Add this additional line at the end of the method body
 return Task.CompletedTask;
 

Hope this will work.