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Creating Custom Performance Monitors

A performance monitor is a feature of the Windows NT/2000 operating system used to determine operating system resource consumption in real-time. In Windows, performance monitors track such statistics as the amount of processing time being consumed on the system, how much memory is free, and how many times the hard disk is accessed. Software subsystems that run on the server can have their own performance monitors, as well: ASP.NET and SQL Server have their own set of performance monitors that broadcast meaningful information to the operating system about resources consumed by these services.

Any .NET application can be equipped with performance monitors that you create yourself, called custom performance monitors. To expose performance information to the operating system, an application must be equipped to do so.

Running the Windows Performance Monitor Utility

You may have used the Perfmon tool to view the status of various performance monitors on a Windows NT or 2000 server. This tool is found in Windows 2000 under Programs, Administrative Tools, Performance. If you've never used Perfmon before, you can see how it works by running it and then right-clicking its main window and selecting Add Counters from the pop-up menu.

After you do this, a Counters dialog box appears, containing lists of every performance monitor–equipped application installed on your machine. We'll assume you have ASP.NET installed on your computer, so select the ASP.NET Applications category from the list labeled Performance Object. Then select the Anonymous Requests/Sec counter from the list of counters. Finally, click Add to add this counter to your view.

You should notice that the chart begins ticking off the number of requests, which should hover close to zero unless you happen to be performing these experiments on a production Web server (if so—shame, shame). To generate some activity for this performance monitor, simply launch a browser and navigate to an ASPX page (not an ASP page) on localhost. Reload the page in the browser a few times by pressing Ctrl+F5, and then flip back to the Performance window. You should be able to see a modest spike in the number of requests per second.

Creating Performance Monitor Categories

The first step in creating a custom performance monitor is to create your own performance monitor category. Performance monitor categories appear in Perfmon's Performance Object drop-down list; they exist as a way to organize the many performance monitors that can exist on a server.


The system provides a number of performance monitor categories, such as Memory, Processor, and so forth. You're not allowed to create performance monitors in these categories. To create a custom performance monitor, you must create your own performance monitor category first.

To create a new performance monitor category, call the Create method of the PerformanceCounterCategory object. This object is a member of System.Diagnostics, so you may want to import that namespace into your application to work with it.

PerformanceCounterCategory.Create is a static method. The method call enables you to create a performance category and a performance object at the same time. This initializes everything you need to begin performance monitoring with only a few lines of code.

Listing 3.7 shows a procedure that creates a performance category called My Category and an associated performance monitor in that category called My Counter.

Listing 3.7 Initializing a New Performance Monitor Category and Performance Monitor Object

public void btnCreateCategory_Click(Object Sender, EventArgs e)
 PerformanceCounterCategory.Create ("My Category", "A category just for me", 
        "My Counter","A counter just for me");
 Label1.Text = "Performance category created.";

This form of the PerformanceCounterCategory.Create method takes the following four strings as parameters:

  • The name of the new category you want to create

  • A text string that describes the category

  • The name of the new performance monitor you want to create

  • A text string that describes the new performance monitor object

After you run this code, your new performance monitor category and performance monitor object are created. Note that if you attempt to run this code twice, you'll get an exception. Also, if you're running Perfmon in the background when this code is executed, you'll need to shut down and restart Perfmon to get it to recognize the new category and performance monitor.

Sending Information to a Performance Monitor from Your Application

To provide information about your application to performance monitors, you first create an instance of the PerformanceCounter object.


The properties, methods, and events of the PerformanceCounter class are summarized in the reference section at the end of this chapter.

Performance counters always represent some kind of integer count related to the performance of the operation being monitored. After you've created a PerformanceCounter object, you have a choice about how you want to send information to it. You can increment and decrement the integer count using the Increment and Decrement methods of the PerformanceCounter object.

Listing 3.8 shows an example of incrementing the performance counter in response to a button click.

Listing 3.8 Incrementing a Performance Monitor Using a PerformanceCounter Object

void Increment_Click(System.Object Sender, System.EventArgs e)
  PerformanceCounter pc = new PerformanceCounter();
  pc.CategoryName = "My Category";
  pc.CounterName = "My Counter";
  pc.ReadOnly = false;

Remember that you must create the performance monitor and its category (described in the previous section) before you can run this code. You can see how this code works by running this code while Perfmon is running in the background. If you have set up a counter for this performance monitor, you should be able to see the graph increase each time you click the button.

In addition to incrementing and decrementing the performance counter object, you can also increase or decrease the value of the counter using the IncrementBy or DecrementBy methods. You can also get or set the raw value of the performance counter by using the RawValue property of the PerformanceCounter object.

Deleting Performance Monitor Categories

You can delete a performance monitor category by executing the Delete method of the PerformanceCounterCategory object. Listing 3.9 shows an example.

Listing 3.9 Deleting a Performance Category

public void btnDeleteCategory_Click(Object Sender, EventArgs e)
  PerformanceCounterCategory.Delete("My Category");

Deleting a performance category deletes all performance monitors associated with that category. If Perfmon is running when you delete a performance category, it will continue monitoring that category; you must shut down and restart Perfmon to see the change.

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