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PerformanceCounterCategory Class

Represents a performance object, which defines a category of performance counters.

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

public sealed class PerformanceCounterCategory
public final class PerformanceCounterCategory
public final class PerformanceCounterCategory

NoteNote

The HostProtectionAttribute attribute applied to this class has the following Resources property value: Synchronization | SharedState. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

NoteImportant:

Creating or deleting a performance counter requires synchronization of the underlying code by using a named mutex. If a highly privileged application locks the named mutex, attempts to create or delete a performance counter causes the application to stop responding until the lock is released. To help avoid this problem, never grant UnmanagedCode permission to untrusted code. In addition, UnmanagedCode permission potentially allows other permissions to be bypassed and should only be granted to highly trusted code.

The PerformanceCounterCategory instance's CategoryName property is displayed in the Performance Object field of the Performance Viewer application's Add Counter dialog box.

The PerformanceCounterCategory class provides several methods for interacting with counters and categories on the computer. The Create methods enable you to define custom categories. The Delete method provides a way to remove categories from the computer. The GetCategories method enables you to view the list of categories, while ReadCategory retrieves all the counter and instance data associated with a single category.

A performance counter publishes performance data about an application. Categories include physical components (such as processors, disks, and memory) and system objects (such as processes and threads). System counters that are related to the same performance object are grouped into a category that indicates their common focus. When you create an instance of the PerformanceCounter class, you first indicate the category with which the component will interact, and then you choose a counter from that category.

For example, one Windows counter category is the Memory category. System counters within this category track memory data such as the number of bytes available and the number of bytes cached. If you wanted to work with the bytes cached in your application, you would create an instance of the PerformanceCounter component, connect it to the Memory category, and then pick the appropriate counter (in this case, Cached Bytes) from that category.

Although your system makes many more counter categories available, the categories that you will probably interact with most frequently are the Cache, Memory, Objects, PhysicalDisk, Process, Processor, Server, System, and Thread categories.

NoteImportant:

The RemoveInstance method in the PerformanceCounter class will release the counter and, if the reuse option is selected for that category, the instance of the counter will be reused. This could cause a race condition if another process or even another part of the code is trying to write to the counter instance.

The following code example determines whether a PerformanceCounter and its PerformanceCounterCategory exist on the local computer or on another computer. If these objects do not exist on the local computer, the example optionally creates them. It uses the Exists method to determine whether the PerformanceCounterCategory exists. If the PerformanceCounterCategory does not exist and no counter name is specified, or if the computer is a remote machine, the example exits.

If a PerformanceCounter name is provided, the example uses the CounterExists method and displays the result to the user. If the PerformanceCounter does not exist, the user can delete and re-create the PerformanceCounterCategory with the new PerformanceCounter. If the user does so, the category is deleted using the Delete method.

If requested, the example now creates the new PerformanceCounterCategory and PerformanceCounter using the Create method. If an instance name is specified, the example uses the InstanceExists method and displays the result.

Imports System
Imports System.Diagnostics
Imports Microsoft.VisualBasic

Module PerfCounterCatCreateExistMod

    Sub Main(ByVal args() As String)
        Dim categoryName As String = ""
        Dim counterName As String = ""
        Dim instanceName As String = ""
        Dim machineName As String = ""
        Dim categoryHelp As String = ""
        Dim counterHelp As String = ""
        Dim objectExists As Boolean = False
        Dim pcc As PerformanceCounterCategory
        Dim createCategory As Boolean = False

        ' Copy the supplied arguments into the local variables.
        Try
            categoryName = args(0)
            counterName = args(1)
            instanceName = args(2)
            machineName = IIf(args(3) = ".", "", args(3))
            categoryHelp = args(4)
            counterHelp = args(5)
        Catch ex As Exception
            ' Ignore the exception from non-supplied arguments.
        End Try

        ' Verify that the category name is not blank.
        If categoryName.Length = 0 Then
            Console.WriteLine("Category name cannot be blank.")
            Return
        End If

        ' Check whether the specified category exists.
        If machineName.Length = 0 Then
            objectExists = _
                PerformanceCounterCategory.Exists(categoryName)

        Else
            ' Handle the exception that is thrown if the computer 
            ' cannot be found.
            Try
                objectExists = PerformanceCounterCategory.Exists( _
                    categoryName, machineName)
            Catch ex As Exception
                Console.WriteLine("Error checking for existence of " & _
                    "category ""{0}"" on computer ""{1}"":" & vbCrLf & _
                    ex.Message, categoryName, machineName)
                Return
            End Try
        End If

        ' Tell the user whether the specified category exists.
        Console.WriteLine("Category ""{0}"" " & _
            IIf(objectExists, "exists on ", "does not exist on ") & _
            IIf(machineName.Length > 0, _
                "computer ""{1}"".", "this computer."), _
            categoryName, machineName)

        ' If no counter name is given, the program cannot continue.
        If counterName.Length = 0 Then
            Return
        End If

        ' A category can only be created on the local computer.
        If Not objectExists Then
            If machineName.Length > 0 Then
                Return
            Else
                createCategory = True
            End If
        Else
            ' Check whether the specified counter exists.
            If machineName.Length = 0 Then
                objectExists = PerformanceCounterCategory.CounterExists( _
                    counterName, categoryName)
            Else
                objectExists = PerformanceCounterCategory.CounterExists( _
                    counterName, categoryName, machineName)
            End If

            ' Tell the user whether the counter exists.
            Console.WriteLine("Counter ""{0}"" " & _
                IIf(objectExists, "exists", "does not exist") & _
                " in category ""{1}"" on " & _
                IIf(machineName.Length > 0, _
                    "computer ""{2}"".", "this computer."), _
                counterName, categoryName, machineName)

            ' If the counter does not exist, consider creating it.
            If Not objectExists Then

                ' If this is a remote computer, 
                ' exit because the category cannot be created.
                If machineName.Length > 0 Then
                    Return
                Else
                    ' Ask whether the user wants to recreate the category.
                    Console.Write("Do you want to delete and recreate " & _
                        "category ""{0}"" with your new counter? [Y/N]: ", _
                        categoryName)
                    Dim userReply As String = Console.ReadLine()

                    ' If yes, delete the category so it can be recreated later.
                    If userReply.Trim.ToUpper.Chars(0) = "Y" Then
                        PerformanceCounterCategory.Delete(categoryName)
                        createCategory = True
                    Else
                        Return
                    End If
                End If
            End If
        End If

        ' Create the category if it was deleted or it never existed.
        If createCategory Then
            pcc = PerformanceCounterCategory.Create( _
                categoryName, categoryHelp, counterName, counterHelp)

            Console.WriteLine( _
                "Category ""{0}"" with counter ""{1}"" created.", _
                pcc.CategoryName, counterName)

        ElseIf instanceName.Length > 0 Then

            ' If an instance name was given, check whether it exists.
            If machineName.Length = 0 Then
                objectExists = PerformanceCounterCategory.InstanceExists( _
                    instanceName, categoryName)
            Else
                objectExists = PerformanceCounterCategory.InstanceExists( _
                    instanceName, categoryName, machineName)
            End If

            ' Tell the user whether the instance exists.
            Console.WriteLine("Instance ""{0}"" " & _
                IIf(objectExists, "exists", "does not exist") & _
                " in category ""{1}"" on " & _
                IIf(machineName.Length > 0, _
                    "computer ""{2}"".", "this computer."), _
                instanceName, categoryName, machineName)
        End If
    End Sub
End Module

System.Object
  System.Diagnostics.PerformanceCounterCategory

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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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