How can an "async" task return an integer and not a public one?-CodePudding

I just had following piece of code, which did not compile:

public Task<int> Handle
{
    var result = <do_something_returning_an_int>();
    ...
    return result;
}

This gives compiler error `cannot implicitly convert type 'int' to 'System.Threading.Thread.Task'.

When I change this into:

async Task<int> Handle
{
    var result = <do_something_returning_an_int>();
    ...
    return result;
}

... no compiler error.

I know that async means that the task does not need to wait for the answer to arrive, but what does this have to do with typecasting?

CodePudding user response：

If you're not awaiting anything in your asynchronous method you omit the async keyword and return a Task instead of the result directly.

public Task<int> Handle
{
    var result = <do_something_returning_an_int>();
    ...
    return Task.FromResult(result);
}

As far as I can tell, doing that only makes sense if other code strictly expects a Task from your method.

This has of course nothing to do with access modifiers, you can combine async with public or any other access modifier.

I'd also recommend taking a look at the documentation

CodePudding user response：

try using task result and then iterate the results

Task<int> Handle
{
    return Task.Run(()=>
    {
       var result = <do_something_returning_an_int>();
       ...
       return result;
    }
}

List<Task<int>> tasks = new List<Task<int>>();
tasks.Add(Handle);
Task.WaitAll(tasks.ToArray());
for(int ctr = 0; ctr < tasks.Count; ctr  ) {
                if (tasks[ctr].Status == TaskStatus.Faulted)
                    output.WriteLine(" Task fault occurred");
                else
                {
                    output.WriteLine("test sent {0}",
                                      tasks[ctr].Result);
                    Assert.True(true);
                }
            }

Task<int> Handle
{
   return Task.FromResult(do_something_returning_an_int);
}