I know that an async method can only return void or Task. I have read similar methods for Exception handling inside async methods. And I'm new to async programming so I am looking for a straightforward solution.
My async method runs an Sql query. If the query was ok, it should notify the caller with a Boolean true and otherwise a false. My method is currently a void so I have no way of knowing.
private async void RefreshContacts()
{
Task refresh = Task.Run(() =>
{
try
{
// run the query
}
catch { }
}
);
await refresh;
}
I simply would like to change async to Task so that in my catch statement the method will return a false and otherwise a true.
It sounds like you just need to return a Task<bool> then:
private async Task<bool> RefreshContactsAsync()
{
try
{
...
}
catch // TODO: Catch more specific exceptions
{
return false;
}
...
return true;
}
Personally I would not catch the exception, instead letting the caller check the task for a faulted state, but that's a different matter.
Change the method signature to Task<bool>. Then if your method is declared as async you can simple return a bool value. But as jon skeet said there are other, possibly better ways, to handle your szenario
private async Task<bool> RefreshContacts()
{
Task refresh = Task.Run(() =>
{
try
{
// run the query
return true;
}
catch { return false;}
}
PS: Another common issue you will possibly have is if you have a method without async. Then you can return Task.FromResult(true) like this:
private Task<bool> RefreshContacts()
{
....
return Task.FromResult(true)
}
Sorry, but I think y'all misleading people here. See the Microsoft article, here.
Very simple example which shows how we can return a (scalar) value of bool, int or string type from a Task.
I am posting the C# code here, for posterity:
using System;
using System.Linq;
using System.Threading.Tasks;
public class Example
{
public static void Main()
{
Console.WriteLine(ShowTodaysInfo().Result);
}
private static async Task<string> ShowTodaysInfo()
{
string ret = $"Today is {DateTime.Today:D}\n" +
"Today's hours of leisure: " +
$"{await GetLeisureHours()}";
return ret;
}
static async Task<int> GetLeisureHours()
{
// Task.FromResult is a placeholder for actual work that returns a string.
var today = await Task.FromResult<string>(DateTime.Now.DayOfWeek.ToString());
// The method then can process the result in some way.
int leisureHours;
if (today.First() == 'S')
leisureHours = 16;
else
leisureHours = 5;
return leisureHours;
}
}
// The example displays output like the following:
// Today is Wednesday, May 24, 2017
// Today's hours of leisure: 5
// </Snippet >