This step-by-step article describes how to use the QueryPerformanceCounter function to time application code.

When you test code to identify performance bottlenecks, you want to use the highest resolution timer that the system has to offer.

NOTE: JScript .NET cannot call Microsoft Windows API functions.

Build and Then Run a Demonstration Application

1. Start Visual Studio .NET or Visual Studio 2005 and create a new Visual C# Console application.
2. Replace the default code with the following code, which times operations in increments of 100:

   using System;
   using System.Runtime.InteropServices;
   
   namespace csConPerfCounter
   {
   	class Class1
   	{
   		[DllImport("kernel32.dll")]
   		extern static short QueryPerformanceCounter(ref long x);
   		[DllImport("kernel32.dll")]
   		extern static short QueryPerformanceFrequency(ref long x);
   
   		static void Main(string[] args)
   		{
   			long ctr1 = 0, ctr2 = 0, freq = 0;
   			int acc = 0, i = 0;
   			if (QueryPerformanceCounter(ref ctr1)!=0)	// Begin timing.
   			{
   				for (i=0; i<100; i++) acc++;		// Code being timed.
   				QueryPerformanceCounter(ref ctr2);	// Finish timing.
   				Console.WriteLine("Start Value: " + ctr1);
   				Console.WriteLine("End Value: " + ctr2);
   				QueryPerformanceFrequency(ref freq);
   				Console.WriteLine("QueryPerformanceCounter minimum resolution: 1" + freq + " seconds.");
   				Console.WriteLine("100 Increment time: " + (ctr2 - ctr1) * 1.0 / freq + " seconds.");
   			}
   			else
   			   Console.WriteLine("High-resolution counter not supported.");
   
   			// Make the console window wait.
   
   			Console.WriteLine();
   			Console.Write("Press Enter to finish ... ");
   			Console.Read();
   		}
   	}
   }
   					

3. Save the application, and press the F5 key to compile and run the application. The console windows should display output similar to the following:

   Start Value: 281060816204
   End Value: 281060816269
   QueryPerformanceCounter minimum resolution: 1/3579545 seconds.
   100 Increment time: 1.81587324646009E-05 seconds.
   
   Press Enter to finish ...
   					

4. Press ENTER to stop running the application and to close the Console window.

Troubleshooting

• This API call may fail under some circumstances. Check the return value and adjust your code to make sure that you receive valid results.
• For best results, test the application multiple times with no other applications or server processes running. Activities in other threads and processes can affect the percentage of time that the system spends in the target application.

For more information, search for "QueryPerformanceCounter" and "QueryPerformanceFrequency" in the Online Help.

For more information about other timers, search for "timeGetTime", "GetTickCount", and "System.DateTime class" in the Online Help.