Task task = AsyncMethod();
// do other stuff
await task;
AsyncMethod() can throw exceptions. Do I put the try-catch around the method invocation, the await, or both?
1 Answer
To avoid the whole debate of where the exception handling should happen, I'll just slightly change your question to: where is it possible to catch exceptions thrown from the AsyncMethod method.
The answer is: where you await it.
Assuming your AsyncMethod method looks something like this:
private async Task AsyncMethod()
{
// some code...
throw new VerySpecificException();
}
... then you can catch the exception this way:
Task task = AsyncMethod();
// do other stuff
try
{
await task;
}
catch(VerySpecificException e) // nice, I can use the correct exception type here.
{
// do something with exception here.
}
Just test it, and you will see how the await keyword does all the work of unwrapping and throwing the exception from the returned Task in a way that it feels very natural to code the try-catch block.
Relevant documentation: try-catch.
Notice what the Exceptions in Async Methods section says:
To catch the exception, await the task in a try block, and catch the exception in the associated catch block.
5 Comments
sstan
@Micky: Yes, but in this case, OP is clearly returning a
Task, which is the normal case.
brettwhiteman
Thanks. Your re-phrase of my question is more what I was asking anyway ;)
brettwhiteman
After reading the linked docs I understand it better - it is actually the
await that causes the exception since the Task is in a faulted state. Makes sense now, thanks heaps @sstansstan
@Brett: Yes, exactly. The await keyword unwraps and throws the exception so that it behaves pretty transparently, and is even nice enough to throw the correct original exception type, rather than the more annoying AggregateException.
sstan
@Dear downvoter: I'm always willing to learn. If I said something wrong, don't be scared about leaving a comment. I won't bite :)
asyncorawaitanywhere in those linked pages.