Why won't my performance counters change?

Question

I must be doing something very wrong here. I create a custom performance counter as follows:

string counterCategory = "Test Category";
string counterName = "Test Counter";

if (!PerformanceCounterCategory.Exists(counterCategory))
{
    Console.WriteLine("Creating Counters");

    CounterCreationDataCollection counterCreationDataCollection =
        new CounterCreationDataCollection();

    counterCreationDataCollection.Add(
        new CounterCreationData(counterName,
        "Description",
        PerformanceCounterType.NumberOfItems32)
    );

    PerformanceCounterCategory.Create(counterCategory,
        "My category description/Help",
        PerformanceCounterCategoryType.SingleInstance,
        counterCreationDataCollection);
}

The counter category and counter are created and viewable in performance monitor.

I then attempt to change the value of the counter

PerformanceCounter myCounter = 
    new PerformanceCounter(counterCategory, counterName, false);

for (int i = 0; i < 10; i++)
{
    Console.WriteLine("Setting to "+i);
    myCounter.RawValue = i;
    Thread.Sleep(200);
}

myCounter.Close();

However as I sit and watch the counter in performance monitor nothing happens, the value never changes.

So what am I doing wrong?

If I add a call to nextValue(), or rawValue() the value from that is returned as I expected but the Windows Performance Monitor still shows a flat line, e.g.

for (int i = 0; i < 10; i++)
{
    Console.WriteLine("Setting to "+i);
    myCounter.IncrementValue()
    Console.WriteLine("Next Value = "+myCounter.RawValue()); 
    Thread.Sleep(200);
}

Edit: I've found that if I close the performance monitor and then reopen it without deleting the counters, that suddenly it realises there's a new value. So the values are being set, and persisting, however Performance Monitor doesn't see the changes.

Answer 1

Are you sure your scale is at a level that will show the changes?

Answer 2

Your code looks good. From my working example the only difference is that I call the increment method after setting the RawValue.

PerformanceCounter myCounter = 
    new PerformanceCounter(counterCategory, counterName, false);

for (int i = 0; i < 10; i++)
{
    Console.WriteLine("Setting to "+i);
    myCounter.Increment();
    Thread.Sleep(200);
}

myCounter.Close();

Answer 3

Is it possible in the course of your testing that you changed the counter name? Your code doesn't verify that the category contains your counter - it only checks if the category exists, and if it does, it doesn't create the category.

If you've changed counter names since the first creation of the category, your new counter would not exist in the category and you might be missing a slight difference in the name of the counter when looking at it in Performance Monitor.

Answer 4

A follow up is in order. It appears, under Win7 anyway, that the performance monitor may not work as expected. When I wrote the test code I paused the application after creating the counters, in order to start the performance monitor. Once I let it continue the monitor never changed it's counters, despite the underlying counter being changed.

If I then quit the performance monitor and restarted it the last counter value in the test program would be shown, indicating that it was being set correctly. If I then ran the test program again, just changing values, performance monitor would finally pick up the changes.

So the code, as everyone indicated is correct, it was the Windows Performance monitor that was misbehaving.

Thank you all for your answers!