rspec/rules/S3216/csharp/rule.adoc

== Why is this an issue?

After an ``++await++``ed ``++Task++`` has executed, you can continue execution in the original, calling thread or any arbitrary thread. Unless the rest of the code needs the context from which the ``++Task++`` was spawned, ``++Task.ConfigureAwait(false)++`` should be used to keep execution in the ``++Task++`` thread to avoid the need for context switching and the possibility of deadlocks.


This rule raises an issue when code in a class library targeting .Net Framework ``++await++``s a ``++Task++`` and continues execution in the original calling thread.

The rule does not raise for .Net Core libraries as there is no ``++SynchronizationContext++`` in .Net Core.


=== Noncompliant code example

[source,csharp]
----
var response = await httpClient.GetAsync(url);  // Noncompliant
----


=== Compliant solution

[source,csharp]
----
var response = await httpClient.GetAsync(url).ConfigureAwait(false);
----


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Add ".ConfigureAwait(false)" to this call to allow execution to continue in any thread.


'''
== Comments And Links
(visible only on this page)

=== on 1 Jul 2015, 15:40:18 Ann Campbell wrote:
Note [~tamas.vajk] that because I anticipate FP's from this rule, I've turned it on in the Security profile but not in SonarQube Way. Unless you're good enough to tell if execution _must_ pick back up in the main thread & ignore those instances?

=== on 2 Jul 2015, 07:02:20 Tamas Vajk wrote:
\[~ann.campbell.2] Thanks, it looks good. We'll see the FPs: we can automatically exclude "exe" projects, ...

=== on 21 Aug 2015, 06:18:04 Tamas Vajk wrote:
\[~ann.campbell.2] Do you think this is a security issue as well?

=== on 21 Aug 2015, 12:24:45 Ann Campbell wrote:
\[~tamas.vajk] I'm kinda in a bind: Critical rules must be bugs or security-related. Since multi-threading issues can affect security, I added the security tag rather than downgrading the severity.

=== on 21 Aug 2015, 12:28:28 Tamas Vajk wrote:
\[~ann.campbell.2] I see. It's more like a bug rule, but it is just a potential bug, so maybe we should reduce the severity to major.

=== on 21 Aug 2015, 12:50:53 Ann Campbell wrote:
Done [~tamas.vajk]

endif::env-github,rspecator-view[]