private static async Task IndependentValuesBetweenContextsHelper <T>()
where T : class, new()
{
var asyncLocal = new Microsoft.VisualStudio.Threading.AsyncLocal <T>();
var player1 = new AsyncAutoResetEvent();
var player2 = new AsyncAutoResetEvent();
await Task.WhenAll(
Task.Run(async delegate
{
Assert.Null(asyncLocal.Value);
var value = new T();
asyncLocal.Value = value;
Assert.Same(value, asyncLocal.Value);
player1.Set();
await player2.WaitAsync();
Assert.Same(value, asyncLocal.Value);
}),
Task.Run(async delegate
{
await player1.WaitAsync();
Assert.Null(asyncLocal.Value);
var value = new T();
asyncLocal.Value = value;
Assert.Same(value, asyncLocal.Value);
asyncLocal.Value = null;
player2.Set();
}));
Assert.Null(asyncLocal.Value);
}
public void ValuePersistsAcrossExecutionContextChanges()
{
var jtLocal = new Microsoft.VisualStudio.Threading.AsyncLocal <object>();
jtLocal.Value = 1;
Func <Task> asyncMethod = async delegate
{
SynchronizationContext.SetSynchronizationContext(new SynchronizationContext());
Assert.Equal(1, jtLocal.Value);
jtLocal.Value = 3;
Assert.Equal(3, jtLocal.Value);
await TaskScheduler.Default;
Assert.Equal(3, jtLocal.Value);
};
asyncMethod().GetAwaiter().GetResult();
Assert.Equal(1, jtLocal.Value);
}
public void AsyncLocalPerfTest()
{
GenericParameterHelper[]? values = Enumerable.Range(1, 50000).Select(n => new GenericParameterHelper(n)).ToArray();
var creates = Stopwatch.StartNew();
for (int i = 0; i < values.Length; i++)
{
this.asyncLocal = new Microsoft.VisualStudio.Threading.AsyncLocal <GenericParameterHelper>();
}
creates.Stop();
var writes = Stopwatch.StartNew();
for (int i = 0; i < values.Length; i++)
{
this.asyncLocal.Value = values[0];
}
writes.Stop();
var reads = Stopwatch.StartNew();
for (int i = 0; i < values.Length; i++)
{
GenericParameterHelper?value = this.asyncLocal.Value;
}
reads.Stop();
// We don't actually validate the perf here. We just print out the results.
this.Logger.WriteLine("Creating {0} instances took {1} ms", values.Length, creates.ElapsedMilliseconds);
this.Logger.WriteLine("Saving {0} values took {1} ms", values.Length, writes.ElapsedMilliseconds);
this.Logger.WriteLine("Reading {0} values took {1} ms", values.Length, reads.ElapsedMilliseconds);
}
public AsyncLocalTests(ITestOutputHelper logger)
: base(logger)
{
this.asyncLocal = new Microsoft.VisualStudio.Threading.AsyncLocal <GenericParameterHelper>();
}
