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PerformanceCounterCategory.ReadCategory Method


Reads all the counter and performance object instance data that is associated with this performance counter category.

 System::Diagnostics::InstanceDataCollectionCollection ^ ReadCategory();
public System.Diagnostics.InstanceDataCollectionCollection ReadCategory ();
member this.ReadCategory : unit -> System.Diagnostics.InstanceDataCollectionCollection
Public Function ReadCategory () As InstanceDataCollectionCollection


An InstanceDataCollectionCollection that contains the counter and performance object instance data for the category.


The CategoryName property is null. The property might not have been set.

A call to an underlying system API failed.

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


The following code example creates a PerformanceCounterCategory for a specified PerformanceCounterCategory name. It then uses ReadCategory to return an InstanceDataCollectionCollection that contains instance data for all the instances of the PerformanceCounter objects within the PerformanceCounterCategory.

// Process the InstanceDataCollectionCollection for this category.
PerformanceCounterCategory pcc = new PerformanceCounterCategory(categoryName);
InstanceDataCollectionCollection idColCol = pcc.ReadCategory();
InstanceDataCollection[] idColArray = new InstanceDataCollection[idColCol.Count];

Console.WriteLine("InstanceDataCollectionCollection for \"{0}\" " +
    "has {1} elements.", categoryName, idColCol.Count);

' Process the InstanceDataCollectionCollection for this category.
Dim pcc As New PerformanceCounterCategory(categoryName)
Dim idColCol As InstanceDataCollectionCollection = pcc.ReadCategory()
Dim idColArray(idColCol.Count - 1) As InstanceDataCollection

Console.WriteLine("InstanceDataCollectionCollection for ""{0}"" " & _
    "has {1} elements.", categoryName, idColCol.Count)


You must set the CategoryName property before you call ReadCategory.

Reading the entire category at once can be as efficient as reading a single counter because of the way that the system provides the data.


To read performance counters from a non-interactive logon session 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.

Applies to

See also