private async Task DispatchSingleAsync(
TKey key,
TaskCompletionSource <TValue> promise,
CancellationToken cancellationToken)
{
var keys = new TKey[] { key };
Activity?activity = DiagnosticEvents.StartSingle(key);
IReadOnlyList <Result <TValue> > results =
await FetchAsync(keys, cancellationToken)
.ConfigureAwait(false);
if (results.Count == 1)
{
SetSingleResult(promise, key, results.First());
}
else
{
Exception error = Errors.CreateKeysAndValuesMustMatch(1,
results.Count);
DiagnosticEvents.ReceivedError(key, error);
promise.SetException(error);
}
DiagnosticEvents.StopSingle(activity, key,
results.Select(r => r.Value).ToArray());
}
private static void SetSingleResult(
TaskCompletionSource <TValue> promise,
TKey key,
Result <TValue> result)
{
if (result.IsError)
{
DiagnosticEvents.ReceivedError(key, result);
promise.SetException(result);
}
else
{
promise.SetResult(result);
}
}
