PerformanceCounter.NextValue Método
Definición
Importante
Parte de la información hace referencia a la versión preliminar del producto, que puede haberse modificado sustancialmente antes de lanzar la versión definitiva. Microsoft no otorga ninguna garantía, explícita o implícita, con respecto a la información proporcionada aquí.
Obtiene un contador de ejemplo y devuelve su valor calculado.
public:
float NextValue();public float NextValue ();member this.NextValue : unit -> singlePublic Function NextValue () As SingleDevoluciones
Siguiente valor calculado que el sistema obtiene para este contador.
Excepciones
La instancia no está correctamente asociada a un contador de rendimiento.
Error de acceso a la API del sistema.
Código que se ejecuta sin privilegios administrativos para intentar leer un contador de rendimiento.
Ejemplos
En el ejemplo de código siguiente se crea un ElapsedTime contador y se usa el método para mostrar los NextValue valores del contador durante un período de tiempo.
#using <System.dll>
using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;
using namespace System::Diagnostics;
using namespace System::Runtime::InteropServices;
void OutputSample( CounterSample s )
{
Console::WriteLine( "\r\n+++++++++++" );
Console::WriteLine( "Sample values - \r\n" );
Console::WriteLine( " BaseValue = {0}", s.BaseValue );
Console::WriteLine( " CounterFrequency = {0}", s.CounterFrequency );
Console::WriteLine( " CounterTimeStamp = {0}", s.CounterTimeStamp );
Console::WriteLine( " CounterType = {0}", s.CounterType );
Console::WriteLine( " RawValue = {0}", s.RawValue );
Console::WriteLine( " SystemFrequency = {0}", s.SystemFrequency );
Console::WriteLine( " TimeStamp = {0}", s.TimeStamp );
Console::WriteLine( " TimeStamp100nSec = {0}", s.TimeStamp100nSec );
Console::WriteLine( "++++++++++++++++++++++" );
}
void CollectSamples()
{
String^ categoryName = "ElapsedTimeSampleCategory";
String^ counterName = "ElapsedTimeSample";
// Create the performance counter category.
if ( !PerformanceCounterCategory::Exists( categoryName ) )
{
CounterCreationDataCollection^ CCDC = gcnew CounterCreationDataCollection;
// Add the counter.
CounterCreationData^ ETimeData = gcnew 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 );
}
// Create the performance counter.
PerformanceCounter^ PC = gcnew PerformanceCounter( categoryName,
counterName,
false );
// Initialize the counter.
PC->RawValue = Stopwatch::GetTimestamp();
DateTime Start = DateTime::Now;
// Loop for the samples.
for ( int j = 0; j < 100; j++ )
{
// Output the values.
if ( (j % 10) == 9 )
{
Console::WriteLine( "NextValue() = {0}", PC->NextValue() );
Console::WriteLine( "Actual elapsed time = {0}", DateTime::Now.Subtract( Start ) );
OutputSample( PC->NextSample() );
}
// Reset the counter on every 20th iteration.
if ( j % 20 == 0 )
{
PC->RawValue = Stopwatch::GetTimestamp();
Start = DateTime::Now;
}
System::Threading::Thread::Sleep( 50 );
}
Console::WriteLine( "Elapsed time = {0}", DateTime::Now.Subtract( Start ) );
}
int main()
{
CollectSamples();
}
using System;
using System.Collections;
using System.Collections.Specialized;
using System.Diagnostics;
using System.Runtime.InteropServices;
public class App
{
public static void Main()
{
CollectSamples();
}
public static void CollectSamples()
{
const String categoryName = "ElapsedTimeSampleCategory";
const String counterName = "ElapsedTimeSample";
// If the category does not exist, create the category and exit.
// Performance counters should not be created and immediately used.
// There is a latency time to enable the counters, they should be created
// prior to executing the application that uses the counters.
// Execute this sample a second time to use the category.
if ( !PerformanceCounterCategory.Exists(categoryName) )
{
CounterCreationDataCollection CCDC = new CounterCreationDataCollection();
// Add the counter.
CounterCreationData ETimeData = new CounterCreationData();
ETimeData.CounterType = PerformanceCounterType.ElapsedTime;
ETimeData.CounterName = counterName;
CCDC.Add(ETimeData);
// Create the category.
PerformanceCounterCategory.Create(categoryName,
"Demonstrates ElapsedTime performance counter usage.",
PerformanceCounterCategoryType.SingleInstance, CCDC);
// Return, rerun the application to make use of the new counters.
return;
}
else
{
Console.WriteLine("Category exists - {0}", categoryName);
}
// Create the performance counter.
PerformanceCounter PC = new PerformanceCounter(categoryName,
counterName,
false);
// Initialize the counter.
PC.RawValue = Stopwatch.GetTimestamp();
DateTime Start = DateTime.Now;
// Loop for the samples.
for (int j = 0; j < 100; j++)
{
// Output the values.
if ((j % 10) == 9)
{
Console.WriteLine("NextValue() = " + PC.NextValue().ToString());
Console.WriteLine("Actual elapsed time = " + DateTime.Now.Subtract(Start).ToString());
OutputSample(PC.NextSample());
}
// Reset the counter on every 20th iteration.
if (j % 20 == 0)
{
PC.RawValue = Stopwatch.GetTimestamp();
Start = DateTime.Now;
}
System.Threading.Thread.Sleep(50);
}
Console.WriteLine("Elapsed time = " + DateTime.Now.Subtract(Start).ToString());
}
private static void OutputSample(CounterSample s)
{
Console.WriteLine("\r\n+++++++++++");
Console.WriteLine("Sample values - \r\n");
Console.WriteLine(" BaseValue = " + s.BaseValue);
Console.WriteLine(" CounterFrequency = " + s.CounterFrequency);
Console.WriteLine(" CounterTimeStamp = " + s.CounterTimeStamp);
Console.WriteLine(" CounterType = " + s.CounterType);
Console.WriteLine(" RawValue = " + s.RawValue);
Console.WriteLine(" SystemFrequency = " + s.SystemFrequency);
Console.WriteLine(" TimeStamp = " + s.TimeStamp);
Console.WriteLine(" TimeStamp100nSec = " + s.TimeStamp100nSec);
Console.WriteLine("++++++++++++++++++++++");
}
}
Imports System.Collections
Imports System.Collections.Specialized
Imports System.Diagnostics
Imports System.Runtime.InteropServices
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.", _
PerformanceCounterCategoryType.SingleInstance, 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(ByVal 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
Comentarios
Nota
Si el valor calculado de un contador depende de dos lecturas de contador, la primera operación de lectura devuelve 0,0. Restablecer las propiedades del contador de rendimiento para especificar un contador diferente equivale a crear un nuevo contador de rendimiento y la primera operación de lectura mediante las nuevas propiedades devuelve 0.0. El tiempo de retraso recomendado entre las llamadas al NextValue método es de un segundo, para permitir que el contador realice la siguiente lectura incremental.
Nota
Para leer los contadores de rendimiento, debe tener privilegios administrativos. En Windows Vista, el control de cuentas de usuario (UAC) determina los privilegios de un usuario. Si es miembro del grupo Administradores integrados, se le asignarán dos símbolos (tokens) de acceso en tiempo de ejecución: un símbolo (token) de acceso de usuario estándar y un símbolo (token) de acceso de administrador. De forma predeterminada, se le asignará el rol de usuario estándar. Para ejecutar el código que accede a los contadores de rendimiento, primero debe elevar los privilegios del usuario estándar al administrador. Para ello, inicie una aplicación haciendo clic con el botón derecho en el icono de la aplicación e indique que desea ejecutarla como administrador.
