public async Task CallbackIsCalled()
{
int attemptCount = 100;
for (int i = 0; i < attemptCount; i++)
{
await checkConcurrentGetOrAdd();
}
async Task checkConcurrentGetOrAdd()
{
var cd = new ConcurrentDictionary <int, int>();
const int key = 42;
bool factoryIsCalled = false;
Task <bool> addTask = Task.Run(() => cd.TryAdd(key, 1));
Task <int> addOrUpdateTask = Task.Run(
() =>
{
return(ConcurrentDictionaryExtensions.GetOrAdd(
cd,
key,
(k, state) =>
{
factoryIsCalled = true;
return 2;
},
factoryArgument: string.Empty));
});
await Task.WhenAll(addTask, addOrUpdateTask);
var addOrUpdateResult = await addOrUpdateTask;
if (factoryIsCalled)
{
// If factory was called, the result can still be obtained from the TryAdd call
addOrUpdateResult.Should().BeInRange(1, 2);
}
else
{
addOrUpdateResult.Should().Be(1);
}
// Printing the outcome just for debugging purposes.
if (factoryIsCalled && addOrUpdateResult == 1)
{
Output.WriteLine("Factory was called, but the race was lost.");
}
if (factoryIsCalled && addOrUpdateResult == 2)
{
Output.WriteLine("Factory was called, and the race was won.");
}
if (!factoryIsCalled)
{
Output.WriteLine("Factory was not called");
}
}
}
public void AddOrGetReturnsFirstResult()
{
var cd = new ConcurrentDictionary <int, int>();
var result = ConcurrentDictionaryExtensions.GetOrAdd(cd, 42,
(key, args) =>
{
return(42);
}, factoryArgument: string.Empty);
result.Should().Be(42);
}