Walkthrough: Retrieving Categories and Counters

The procedures in this walkthrough take you through the process of creating and configuring PerformanceCounter component instances and using them to retrieve lists of performance counter categories and counters on your system. A performance counter is the means by which Windows collects performance data on various system resources. Windows contains a set of predefined counters, organized into categories, with which you can interact. Each category and counter is related to a specific area of system functionality.

In this walkthrough you will:

• Instantiate a PerformanceCounter component and configure it to interact with a specific category of system-generated counters.

• Create a Windows application that displays information about categories and counters in a list box.

• Use the GetCategories method to return a list of categories on the local computer.

• Use the GetCounters method to return a list of counters from the specified category.

To create your Windows application

1. From the New Project dialog box, create a Visual Basic or Visual C# Windows Application.

2. From the Windows Forms tab of the Toolbox, add two buttons and two list boxes to your form. Arrange them in any order you like, and then set the following properties for them:

   Control	Property	Value
   Button1	Name	btnGetCounters
   	Text	Get Counters
   Button2	Name	btnGetCategories
   	Text	Get Categories
   ListBox1	Name	lstCounters
   	ScrollAlwaysVisible	True
   ListBox2	Name	lstCategories
   	ScrollAlwaysVisible	True

3. Save your work.

To retrieve the category list

1. In Design view, double-click the Get Categories button to access the Code Editor.

2. In the btnGetCategories_Click procedure, add the following code to retrieve the list of categories from the local computer.

   Private Sub btnGetCategories_Click(ByVal sender As System.Object, _
      ByVal e As System.EventArgs) Handles btnGetCategories.Click
   
      Dim myCat2 As PerformanceCounterCategory()
      Dim i As Integer 
      ' Remove the current contents of the list. 
      Me.lstCategories.Items.Clear()
      ' Retrieve the categories.
      myCat2 = PerformanceCounterCategory.GetCategories
      ' Add the retrieved categories to the list. 
      For i = 0 To myCat2.Length - 1
         Me.lstCategories.Items.Add(myCat2(i).CategoryName)
      Next 
   End Sub
   

   private void btnGetCategories_Click(object sender, System.EventArgs e)
   {
      System.Diagnostics.PerformanceCounterCategory[] myCat2;
      // Remove the current contents of the list.
      this.lstCategories.Items.Clear();
      // Retrieve the categories.
      myCat2 = 
         System.Diagnostics.PerformanceCounterCategory.GetCategories();
      // Add the retrieved categories to the list.
      for (int i = 0; i < myCat2.Length; i+) 
      {
         this.lstCategories.Items.Add(myCat2[i].CategoryName);
      }
   }
   

To retrieve the counter list

1. In Design view, double-click the Get Counters button to access the Code Editor. The insertion point will be positioned in the btnGetCounters_Click event.

2. Add the following code to retrieve the list of counters from the selected category.

   Private Sub btnGetCounters_Click(ByVal sender As System.Object, _
      ByVal e As System.EventArgs) Handles btnGetCounters.Click
   
      Dim instanceNames() As String 
      Dim counters As New System.Collections.ArrayList()
   
      If (Me.lstCategories.SelectedIndex <> -1) Then 
         Dim mycat As New PerformanceCounterCategory( _
            Me.lstCategories.SelectedItem.ToString())
         ' Remove the current contents of the list. 
         Me.lstCounters.Items.Clear()
         ' Retrieve the counters. 
         Try
            instanceNames = mycat.GetInstanceNames()
            If (instanceNames.Length = 0) Then
               counters.AddRange(mycat.GetCounters())
            Else 
               Dim i As Integer 
               For i = 0 To instanceNames.Length - 1
                  counters.AddRange( _
                     mycat.GetCounters(instanceNames(i)))
               Next 
            End If 
            ' Add the retrieved counters to the list. 
            Dim counter As PerformanceCounter
            For Each counter In counters
               Me.lstCounters.Items.Add(counter.CounterName)
            Next 
         Catch ex As Exception
            MessageBox.Show( _
               "Unable to list the counters for this category:" _
               & ControlChars.CrLf & ex.Message)
         End Try 
      End If 
   End Sub
   

   private void btnGetCounters_Click(object sender, System.EventArgs e)
   {
      string[] instanceNames;
      System.Collections.ArrayList counters = new 
         System.Collections.ArrayList();
      if (this.lstCategories.SelectedIndex != -1) 
      {
         System.Diagnostics.PerformanceCounterCategory mycat = new 
            System.Diagnostics.PerformanceCounterCategory(
            this.lstCategories.SelectedItem.ToString());
         // Remove the current contents of the list.
         this.lstCounters.Items.Clear();
         // Retrieve the counters.
         try 
         {
            instanceNames = mycat.GetInstanceNames();
            if (instanceNames.Length == 0) 
            {
               counters.AddRange(mycat.GetCounters());
            }
            else
            {
               for (int i = 0; i < instanceNames.Length; i+)
               {
                  counters.AddRange(mycat.GetCounters(instanceNames[i]));
               }
            }
   
            // Add the retrieved counters to the list.
            foreach (System.Diagnostics.PerformanceCounter counter 
               in counters) 
            {
               this.lstCounters.Items.Add(counter.CounterName);
            }
         }
         catch (System.Exception ex)
         {
            MessageBox.Show(
               "Unable to list the counters for this category:\n" 
               + ex.Message);
         }
      }
   }
   

To test your application

1. Save and compile your application.

2. Click the Get Categories button. You will see a list of categories in the list box.

3. Select one of the categories and click the Get Counters button. You will see a list of the counters for the selected category.

See Also

Concepts

Introduction to Monitoring Performance Thresholds

Other Resources

Monitoring Performance Thresholds

Performance Counter Walkthroughs