Here's the page code:

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<%@ Page Language="C#" ContentType="text/xml" %>
<%@ Import namespace="System.Diagnostics" %>
<%@ Import namespace="System.Xml" %>
<script language="C#" runat="server">

static int PERF_TYPE_NUMBER  = 0x00000000;  // a number (not a counter)
static int PERF_TYPE_COUNTER  = 0x00000400;  // an increasing numeric value
static int PERF_TYPE_TEXT   = 0x00000800;  // a text field
static int PERF_TYPE_ZERO   = 0x00000C00;  // displays a zero

static int PERF_COUNTER_VALUE  = 0x00000000;  // display counter value
static int PERF_COUNTER_RATE  = 0x00010000;  // divide ctr / delta time
static int PERF_COUNTER_FRACTION = 0x00020000;  // divide ctr / base
static int PERF_COUNTER_BASE  = 0x00030000;  // base value used in
fractions
static int PERF_COUNTER_ELAPSED = 0x00040000;  // subtract counter from
current time
static int PERF_COUNTER_QUEUELEN = 0x00050000;  // Use Queuelen processing
func.
static int PERF_COUNTER_HISTOGRAM = 0x00060000;  // Counter begins or ends
a histogram
static int PERF_COUNTER_PRECISION = 0x00070000;  // divide ctr / private
clock

static int PERF_TIMER_TICK   = 0x00000000;  // use system perf. freq for
base
static int PERF_TIMER_100NS  = 0x00100000;  // use 100 NS timer time base
units
static int PERF_OBJECT_TIMER  = 0x00200000;  // use the object timer freq

public void Page_Load(Object sender, EventArgs e)
{
   // Result Document
   XmlDocument PerformanceDocument = new XmlDocument();
   XmlElement PerformanceElement =
PerformanceDocument.CreateElement("performance");

PerformanceDocument.AppendChild(PerformanceDocument.CreateProcessingInstruct
ion("xml", "version=\"1.0\" encoding=\"UTF-8\""));
   PerformanceDocument.AppendChild(PerformanceElement);
   SampleSystemPerformance(PerformanceElement);

   // Render the Document
   XmlTextWriter XmlOutputWriter = new XmlTextWriter(Response.Output);

   PerformanceDocument.WriteTo(XmlOutputWriter);
   XmlOutputWriter.Close();
}

void SampleSystemPerformance(XmlElement PerformanceElement)
{
 // System Counters
 RenderCounterSample(PerformanceElement, "Processor\\% Processor
Time\\_Total");
 RenderCounterSample(PerformanceElement, "Memory\\Available Mbytes");
 RenderCounterSample(PerformanceElement, "Memory\\Pages/sec");
 RenderCounterSample(PerformanceElement, "System\\Context Switches/sec");
 RenderCounterSample(PerformanceElement, "Process\\Handle
Count\\aspnet_wp");
}

PerformanceCounter CreatePerformanceCounter(string CounterName)
{
 if( CounterName == null )
 {
  throw new ArgumentNullException();
 }

 // Create Counter
 string[]  Components = CounterName.Split('\\');

 if( Components.Length == 2 )
 {
  return new PerformanceCounter(Components[0], Components[1]);
 }
 else if( Components.Length == 3 )
 {
  return new PerformanceCounter(Components[0], Components[1],
Components[2]);
 }
 else if( Components.Length == 4 )
 {
  return new PerformanceCounter(Components[0], Components[1],
Components[2], Components[3]);
 }

 throw new ArgumentException();
}

void RenderCounterSample(XmlElement ParentElement, string CounterName)
{
 RenderCounterSample(ParentElement, CounterName,
CreatePerformanceCounter(CounterName).NextSample());
}

void RenderCounterSample(XmlElement ParentElement, string CounterName,
CounterSample Sample)
{
 XmlElement  SampleElement =
ParentElement.OwnerDocument.CreateElement("counter-sample");

 long   CounterType = (int)Sample.CounterType & 0x00000C00;
 long   CounterSubtype = (int)Sample.CounterType & 0x000F0000;
 long   TimerBase = (int)Sample.CounterType & 0x00300000;

 SampleElement.SetAttribute("counter", CounterName);
 SampleElement.SetAttribute("counter-type",
((int)Sample.CounterType).ToString("X08"));
 SampleElement.SetAttribute("raw-value", Sample.RawValue.ToString());

 if( CounterType == PERF_TYPE_NUMBER )
 {
  // The value is enough for this counter
 }
 else if( CounterType == PERF_TYPE_COUNTER )
 {
  if( CounterSubtype == PERF_COUNTER_VALUE )
  {
  }
  else if( CounterSubtype == PERF_COUNTER_RATE )
  {
   // Time
   if( TimerBase == PERF_TIMER_TICK )
   {
    SampleElement.SetAttribute("time-stamp", Sample.TimeStamp.ToString());
    SampleElement.SetAttribute("system-frequency",
Sample.SystemFrequency.ToString());
   }
   else if( TimerBase == PERF_TIMER_100NS )
   {
    SampleElement.SetAttribute("time-stamp-100nsec",
Sample.TimeStamp100nSec.ToString());
   }
   else if( TimerBase == PERF_OBJECT_TIMER )
   {
   }
  }
 }

 ParentElement.AppendChild(SampleElement);
}
</script>

Add any namespaces it needs, I didn't post the whole page for clarity so I
might have left some out. If you run this under Windows 2000 Server (NOT
Win2k3, it works fine there) you will see that the handle count for
aspnet_wp will keep going up untill the application restarts. It eats 9
handles per counter, so feel free to add more counters to speed up the
process (Asp.Net app restarts once you get to 4 or 5 thousand handles).

And just to let you know - calling PerformanceCounter.Close on those counter
objects does not help, if you want to go ahead and change
RenderCounterSample to this:

void RenderCounterSample(XmlElement ParentElement, string CounterName)
{
   PerformanceCounter  Counter = CreatePerformanceCounter(CounterName);
   RenderCounterSample(ParentElement, CounterName, Counter.NextSample());
   Counter.Close();
}

I  eventually used WMI to gather the performance counters I need but I think
that's less than ideal solution. And of course the code is not finished, it
will not render all the information needed for all counter types but it
works for the ones I'm watching. I'll add more when I need it.

Jerry