new PerformanceCounter(".NET CLR Memory", "# bytes in all heaps", Process.GetCurrentProcess().ProcessName);

string[] categories = PerformanceCounterCategory.GetCategories().Select(c => c.CategoryName).OrderBy(s => s).ToArray();
string toInspect = string.Join(",rn", categories);

System.Text.StringBuilder interestingToInspect = new System.Text.StringBuilder();
string[] interestingCategories = categories.Where(s => s.StartsWith(".NET") || s.Contains("Memory")).ToArray();
foreach (string interestingCategory in interestingCategories)
{
    PerformanceCounterCategory cat = new PerformanceCounterCategory(interestingCategory);
    foreach (PerformanceCounter counter in cat.GetCounters())
    {
        interestingToInspect.AppendLine(interestingCategory + ":" + counter.CounterName);
    }
}
toInspect = interestingToInspect.ToString();

foreach (var instance in cat.GetInstanceNames())
{
    foreach (PerformanceCounter counter in cat.GetCounters(instance))
    {
        interestingToInspect.AppendLine(interestingCategory + ":" + counter.CounterName);
    }
}

new PerformanceCounter(".NET CLR Memory", "# bytes in all heaps", Process.GetCurrentProcess().ProcessName, true);

public static string GetInstanceNameForProcessId(int pid)
    {
        var cat = new PerformanceCounterCategory(".NET CLR Memory");
        foreach (var instanceName in cat.GetInstanceNames())
        {
            using (var pcPid = new PerformanceCounter(cat.CategoryName, "Process ID", instanceName))
            {
                if ((int)pcPid.NextValue() == pid)
                {
                    return instanceName;
                }
            }
        }

        throw new ArgumentException(
            string.Format("No performance counter instance found for process id '{0}'", pid),
            "pid");
    }