PerformanceCounterCategory.InstanceExists Method (String, String, String)


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Determines whether a specified category on a specified computer contains the specified performance object instance.

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

public static bool InstanceExists(
	string instanceName,
	string categoryName,
	string machineName


Type: System.String

The performance object instance to search for.

Type: System.String

The performance counter category to search.

Type: System.String

The name of the computer on which to look for the category instance pair.

Return Value

Type: System.Boolean

true if the category contains the specified performance object instance; otherwise, false.

Exception Condition

The instanceName parameter is null.


The categoryName parameter is null.


The categoryName parameter is an empty string ("").


The machineName parameter is invalid.


A call to an underlying system API failed.


Code that is executing without administrative privileges attempted to read a performance counter.

It is not possible to determine whether a performance object instance exists on a computer without specifying a specific category to look in.

You can use "." to specify the local computer.


To read performance counters in Windows Vista and later, Windows XP Professional x64 Edition, or Windows Server 2003, you must either be a member of the Performance Monitor Users group or have administrative privileges.

To avoid having to elevate your privileges to access performance counters in Windows Vista and later, add yourself to the Performance Monitor Users group.

In Windows Vista and later, User Account Control (UAC) determines the privileges of a user. If you are a member of the Built-in Administrators group, you are assigned two run-time access tokens: a standard user access token and an administrator access token. By default, you are in the standard user role. To execute the code that accesses performance counters, you must first elevate your privileges from standard user to administrator. You can do this when you start an application by right-clicking the application icon and indicating that you want to run as an administrator.

The following code example uses the static overloads of InstanceExists to determine whether the given PerformanceCounter instance exists in the PerformanceCounterCategory. The overload is selected based on whether a computer name is specified. If no instance name is specified, the example uses the default single-instance name.

public static void Main(string[] args)
    string categoryName = "";
    string instanceName = "";
    string machineName = "";
    bool objectExists = false;
    const string SINGLE_INSTANCE_NAME = "systemdiagnosticsperfcounterlibsingleinstance";

    // Copy the supplied arguments into the local variables.
        categoryName = args[0];
        instanceName = args[1];
        machineName = args[2]=="."? "": args[2];
    catch(Exception ex)
        // Ignore the exception from non-supplied arguments.

    // Use the given instance name or use the default single-instance name.
    if (instanceName.Length==0)
        instanceName = SINGLE_INSTANCE_NAME;

        // Check whether the specified instance exists.
        // Use the static forms of the InstanceExists method.
        if (machineName.Length==0)
            objectExists = PerformanceCounterCategory.InstanceExists(instanceName, categoryName);
            objectExists = PerformanceCounterCategory.InstanceExists(instanceName, categoryName, machineName);

    catch(Exception ex)
        Console.WriteLine("Unable to check for the existence of " +
            "instance \"{0}\" in category \"{1}\" on " + 
            (machineName.Length>0? "computer \"{2}\":": "this computer:") + "\n" + 
            ex.Message, instanceName, categoryName, machineName);

    // Tell the user whether the instance exists.
    Console.WriteLine("Instance \"{0}\" " + (objectExists? "exists": "does not exist") + 
        " in category \"{1}\" on " + (machineName.Length>0? "computer \"{2}\".": "this computer."), 
        instanceName, categoryName, machineName);


for reading performance counter categories. Associated enumeration: PerformanceCounterPermissionAccess.Read.

.NET Framework
Available since 1.1
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