Stopwatch class in C#

The Stopwatch class in C# is used to measure elapsed time with high precision. It provides accurate timing measurements for performance monitoring and benchmarking applications. The class is found in the System.Diagnostics namespace.

Syntax

Following is the syntax for creating and starting a Stopwatch −

Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();

Alternatively, you can create and start in one line −

Stopwatch stopwatch = Stopwatch.StartNew();

Key Properties and Methods

Using Stopwatch for Basic Timing

The following example demonstrates basic Stopwatch usage to measure elapsed time −

using System;
using System.Diagnostics;
using System.Threading;

public class Demo {
    public static void Main() {
        var sw = Stopwatch.StartNew();
        
        // Simulate some work
        Thread.Sleep(1000);
        
        sw.Stop();
        
        Console.WriteLine("Elapsed Ticks: " + sw.ElapsedTicks);
        Console.WriteLine("Elapsed Milliseconds: " + sw.ElapsedMilliseconds);
        Console.WriteLine("Elapsed Time: " + sw.Elapsed);
    }
}

The output of the above code is −

Elapsed Ticks: 10001234
Elapsed Milliseconds: 1000
Elapsed Time: 00:00:01.0001234

Using Stopwatch to Measure Function Performance

Here's an example that measures the execution time of different operations −

using System;
using System.Diagnostics;
using System.Linq;

public class PerformanceTest {
    public static void Main() {
        // Test array creation and initialization
        var sw1 = Stopwatch.StartNew();
        int[] numbers = Enumerable.Range(1, 1000000).ToArray();
        sw1.Stop();
        
        // Test array sum calculation
        var sw2 = Stopwatch.StartNew();
        long sum = numbers.Sum();
        sw2.Stop();
        
        Console.WriteLine("Array creation took: " + sw1.ElapsedMilliseconds + " ms");
        Console.WriteLine("Sum calculation took: " + sw2.ElapsedMilliseconds + " ms");
        Console.WriteLine("Total sum: " + sum);
    }
}

The output of the above code is −

Array creation took: 45 ms
Sum calculation took: 2 ms
Total sum: 500000500000

Using Start, Stop, and Reset Methods

This example shows how to control the Stopwatch with different methods −

using System;
using System.Diagnostics;
using System.Threading;

public class StopwatchControl {
    public static void Main() {
        Stopwatch sw = new Stopwatch();
        
        // Start timing
        sw.Start();
        Thread.Sleep(500);
        Console.WriteLine("After 500ms: " + sw.ElapsedMilliseconds + " ms");
        
        // Stop timing
        sw.Stop();
        Thread.Sleep(300); // This won't be counted
        Console.WriteLine("After stop (300ms sleep): " + sw.ElapsedMilliseconds + " ms");
        
        // Resume timing
        sw.Start();
        Thread.Sleep(200);
        Console.WriteLine("After resume + 200ms: " + sw.ElapsedMilliseconds + " ms");
        
        // Reset and restart
        sw.Restart();
        Thread.Sleep(100);
        Console.WriteLine("After restart + 100ms: " + sw.ElapsedMilliseconds + " ms");
    }
}

The output of the above code is −

After 500ms: 500 ms
After stop (300ms sleep): 500 ms
After resume + 200ms: 700 ms
After restart + 100ms: 100 ms

Common Use Cases

• Performance benchmarking − Comparing execution times of different algorithms.

• Timeout implementation − Measuring if an operation exceeds a time limit.

• Profiling applications − Identifying performance bottlenecks in code.

• Game development − Measuring frame times and animation durations.

Conclusion

The Stopwatch class in C# provides high-precision timing capabilities essential for performance measurement and benchmarking. It offers multiple time representations (ticks, milliseconds, TimeSpan) and flexible control methods for accurate timing in various scenarios.