A quick app to test the latency overhead of asynchronous calls in .NET.

Program.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Reflection;

namespace ConsoleApplication6
{
    class Program
    {
        static void Main()
        {
            const int count = 1000000;
            var filePath = Path.GetTempFileName();
            File.WriteAllBytes(filePath, new byte[count]);

            Console.WriteLine("File length: {0} bytes.", new FileInfo(filePath).Length);
            RunTimedOperation(filePath, "Preload", (fs, b) => fs.Read(b, 0, 1), 100);
            RunTimedOperation(filePath, "Asynchronous", (fs, b) => fs.ReadAsync(b, 0, 1).Wait(), count);
            RunTimedOperation(filePath, "Synchronous", (fs, b) => fs.Read(b, 0, 1), count);
        }

        static void RunTimedOperation(string filePath, string operationName, Action<FileStream, byte[]> operation, int count)
        {
            Console.WriteLine("Running {0} loops of {1}...", count, operationName);
            var timer = Stopwatch.StartNew();
            using (var file = File.OpenRead(filePath))
            {
                var buffer = new byte[1];
                for (int i = 0; i != count; ++i)
                {
                    operation(file, buffer);
                }
            }
            long elapsedMilliseconds = timer.ElapsedMilliseconds;
            Console.WriteLine("Done in {0} ms.", elapsedMilliseconds);
        }
    }
}