public PerformanceCounterSampleSet ReadNextSet()
{
this._firstRead.Wait();
long fileTimeStamp = 0;
uint returnCode = this._isPreVista ? Apis.PdhCollectQueryData(this._safeQueryHandle)
: Apis.PdhCollectQueryDataWithTime(this._safeQueryHandle, ref fileTimeStamp);
if (this._isLastSampleBad)
{
return(null);
}
if (returnCode != PdhResults.PDH_CSTATUS_VALID_DATA)
{
//this makes sure next call to ReadNextSet doesn't examine the data, and just returns null
this._isLastSampleBad = true;
return(null);
}
DateTime now = (_isPreVista || returnCode == PdhResults.PDH_NO_DATA) ? DateTime.Now :
new DateTime(DateTime.FromFileTimeUtc(fileTimeStamp).Ticks, DateTimeKind.Local);
PerformanceCounterSample[] counterSamples = new PerformanceCounterSample[this._consumerPathToHandleAndInstanceMap.Count];
int samplesRead = 0;
foreach (string key in this._consumerPathToHandleAndInstanceMap.Keys)
{
IntPtr counterHandle = this._consumerPathToHandleAndInstanceMap[key].CounterHandle;
CounterInfo info = PdhHelper.GetCounterInfo(counterHandle);
var sample = GetRawCounterSample(counterHandle, key, info, now);
var performanceSample = sample.PerformanceCounterSample ?? GetFormattedCounterSample(counterHandle, key, info, sample.RawCounter);
if (!this._ignoreBadStatusCodes && (performanceSample.Status != 0))
{
throw BuildException(performanceSample.Status);
}
if (performanceSample.Status != 0)
{
_log.Info(() => string.Format("Status {0:x} ignored for counter {1}", performanceSample.Status, key));
continue;
}
counterSamples[samplesRead++] = performanceSample;
}
this._isLastSampleBad = false;
//in the event we skipped bad data
if (samplesRead < counterSamples.Length)
{
Array.Resize(ref counterSamples, samplesRead);
}
return(new PerformanceCounterSampleSet(this._isPreVista ? counterSamples[samplesRead].Timestamp : now, counterSamples));
}
private void PerformFirstRead()
{
long fileTimeStamp = 0;
if (this._isPreVista)
{
Apis.PdhCollectQueryData(this._safeQueryHandle);
}
else
{
Apis.PdhCollectQueryDataWithTime(this._safeQueryHandle, ref fileTimeStamp);
}
//a sneaky way of not blocking until we actually call ReadNext
this._backgroundTimer.Start();
}