public async Task AsyncMethodReturnsTaskOfT()
{
const string expected = "foo";
var actual = await AsyncMethods
.WaitASecondAndReturnAValueAsync(expected);
Assert.AreEqual(expected, actual);
}
public void SomeProblemWithGetAwaiterGetResult()
{
var blockingSyncContext = new WindowsFormsSynchronizationContext();
SynchronizationContext.SetSynchronizationContext(blockingSyncContext);
var theValue = AsyncMethods
.WaitASecondAndReturnAValueAsync("this too is doomed")
.GetAwaiter()
.GetResult();
}
public void ItCreatesADeadLockWhenCertainSyncContextsGetInvolved()
{
var blockingSyncContext = new WindowsFormsSynchronizationContext();
SynchronizationContext.SetSynchronizationContext(blockingSyncContext);
// Result is invoked on the same thread as the blocking sync context
// Because the sync context blocked when calling the async method,
// The call to result is deadlocked as it's waiting for the original call
// to release the thread.
// A way to see this visually is to execute this from a GUI, it would become non responsive.
var theValue = AsyncMethods
.WaitASecondAndReturnAValueAsync("this is doomed to deadlock")
.Result;
}
public void HowDoIFixThisDeadLockByAllowingCompletionOnADifferentThread()
{
var blockingSyncContext = new WindowsFormsSynchronizationContext();
SynchronizationContext.SetSynchronizationContext(blockingSyncContext);
Func <Task <string> > returnValueFunc = () => AsyncMethods
.WaitASecondAndReturnAValueAsync("this works around it");
//this now executes on a different thread
//and wont deadlock when calling result
var theValue = Task
.Run(returnValueFunc)
.Result;
Assert.AreEqual("this works around it", theValue);
}