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PerformanceCounter.NextValue Method

Obtains a counter sample and returns the calculated value for it.

Namespace: System.Diagnostics
Assembly: System (in system.dll)

'Declaration
Public Function NextValue As Single
'Usage
Dim instance As PerformanceCounter
Dim returnValue As Single

returnValue = instance.NextValue
public float NextValue ()
public function NextValue () : float

Return Value

The next calculated value that the system obtains for this counter.

Exception typeCondition

InvalidOperationException

The instance is not correctly associated with a performance counter.

Win32Exception

An error occurred when accessing a system API.

PlatformNotSupportedException

The platform is Windows 98 or Windows Millennium Edition (Me), which does not support performance counters.

NoteNote

If the calculated value of a counter depends on two counter reads, the first read returns 0.0.


Imports System
Imports System.Collections
Imports System.Collections.Specialized
Imports System.Diagnostics
Imports System.Runtime.InteropServices
Imports Microsoft.VisualBasic

Public Class App
   
   Public Shared Sub Main()
      CollectSamples()
   End Sub
   
   Private Shared Sub CollectSamples()

      Dim categoryName as String = "ElapsedTimeSampleCategory"
      Dim counterName as String = "ElapsedTimeSample"

      If Not PerformanceCounterCategory.Exists(categoryName) Then
         
         Dim CCDC As New CounterCreationDataCollection()
         
         ' Add the counter.
         Dim ETimeData As New CounterCreationData()
         ETimeData.CounterType = PerformanceCounterType.ElapsedTime
         ETimeData.CounterName = counterName
         CCDC.Add(ETimeData)
         
         ' Create the category.
         PerformanceCounterCategory.Create(categoryName, _
            "Demonstrates ElapsedTime performance counter usage.", CCDC)
       
      Else
         Console.WriteLine("Category exists - {0}", categoryName)
      End If

      ' Create the counter.
      Dim PC As PerformanceCounter
      PC = New PerformanceCounter(categoryName, counterName, False)
     
      ' Initialize the counter.
      PC.RawValue = Stopwatch.GetTimestamp()

      Dim Start As DateTime = DateTime.Now
      
      ' Loop for the samples.
      Dim j As Integer
      For j = 0 To 99
         ' Output the values.
         If j Mod 10 = 9 Then
            Console.WriteLine(("NextValue() = " _
                + PC.NextValue().ToString()))
            Console.WriteLine(("Actual elapsed time = " _
                + DateTime.Now.Subtract(Start).ToString()))
            OutputSample(PC.NextSample())
         End If
         
         ' Reset the counter every 20th iteration.
         If j Mod 20 = 0 Then
            PC.RawValue = Stopwatch.GetTimestamp()
            Start = DateTime.Now
         End If
         System.Threading.Thread.Sleep(50)
      Next j
      
      Console.WriteLine(("Elapsed time = " + _
            DateTime.Now.Subtract(Start).ToString()))
   End Sub 
   
   
   Private Shared Sub OutputSample(s As CounterSample)
      Console.WriteLine(ControlChars.Lf + ControlChars.Cr + "+++++++")

      Console.WriteLine("Sample values - " + ControlChars.Cr _
            + ControlChars.Lf)
      Console.WriteLine(("   BaseValue        = " _
            + s.BaseValue.ToString()))
      Console.WriteLine(("   CounterFrequency = " + _
            s.CounterFrequency.ToString()))
      Console.WriteLine(("   CounterTimeStamp = " + _
            s.CounterTimeStamp.ToString()))
      Console.WriteLine(("   CounterType      = " + _
            s.CounterType.ToString()))
      Console.WriteLine(("   RawValue         = " + _
            s.RawValue.ToString()))
      Console.WriteLine(("   SystemFrequency  = " + _
            s.SystemFrequency.ToString()))
      Console.WriteLine(("   TimeStamp        = " + _
            s.TimeStamp.ToString()))
      Console.WriteLine(("   TimeStamp100nSec = " + _
            s.TimeStamp100nSec.ToString()))
      
      Console.WriteLine("+++++++")
   End Sub
End Class

import System.*;
import System.Collections.*;
import System.Collections.Specialized.*;
import System.Diagnostics.*;
import System.Runtime.InteropServices.*;

public class App
{
    public static void main(String[] args)
    {
        CollectSamples();
    } //main

    public static void CollectSamples()
    {
        final String categoryName = "ElapsedTimeSampleCategory";
        final String counterName = "ElapsedTimeSample";

        if (!(PerformanceCounterCategory.Exists(categoryName))) {
            CounterCreationDataCollection ccdc = 
                new CounterCreationDataCollection();
            // Add the counter.
            CounterCreationData eTimeData = new CounterCreationData();
            eTimeData.set_CounterType(PerformanceCounterType.ElapsedTime);
            eTimeData.set_CounterName(counterName);
            ccdc.Add(eTimeData);
            // Create the category.
            PerformanceCounterCategory.Create(categoryName, 
                "Demonstrates ElapsedTime performance counter usage.", ccdc);
        }
        else {
            Console.WriteLine("Category exists - {0}", categoryName);
        }
        // Create the performance counter.
        PerformanceCounter pc = new PerformanceCounter(categoryName,
            counterName, false);
        // Initialize the counter.
        pc.set_RawValue(Stopwatch.GetTimestamp());
        DateTime start = DateTime.get_Now();
        // Loop for the samples.
        for (int j = 0; j < 100; j++) {
            // Output the values.
            if (j % 10 == 9) {
                Console.WriteLine("NextValue() = " + ((Single)pc.NextValue()).
                    ToString());
                Console.WriteLine("Actual elapsed time = "
                    + DateTime.get_Now().Subtract(start).ToString());
                OutputSample(pc.NextSample());
            }
            // Reset the counter on every 20th iteration.
            if (j % 20 == 0) {
                pc.set_RawValue(Stopwatch.GetTimestamp());
                start = DateTime.get_Now();
            }
            System.Threading.Thread.Sleep(50);
        }
        Console.WriteLine("Elapsed time = " + DateTime.get_Now().
            Subtract(start).ToString());
    } //CollectSamples

    private static void OutputSample(CounterSample s)
    {
        Console.WriteLine("\r\n+++++++++++");
        Console.WriteLine("Sample values - \r\n");
        Console.WriteLine("   BaseValue        = " + s.get_BaseValue());
        Console.WriteLine("   CounterFrequency = " + s.get_CounterFrequency());
        Console.WriteLine("   CounterTimeStamp = " + s.get_CounterTimeStamp());
        Console.WriteLine("   CounterType      = " + s.get_CounterType());
        Console.WriteLine("   RawValue         = " + s.get_RawValue());
        Console.WriteLine("   SystemFrequency  = " + s.get_SystemFrequency());
        Console.WriteLine("   TimeStamp        = " + s.get_TimeStamp());
        Console.WriteLine("   TimeStamp100nSec = " + s.get_TimeStamp100nSec());
        Console.WriteLine("++++++++++++++++++++++");
    } //OutputSample
} //App

Windows 98, Windows 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0
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