Test Async in CSharp

TestAsync.cs

class Program
{
    static async Task DoSomethingAsync()
    {
        int val = 13;

        await Task.Delay(TimeSpan.FromSeconds(1));

        val *= 2;

        await Task.Delay(TimeSpan.FromSeconds(1));

        Console.Out.WriteLine(val);
    }

    static async Task<string> DownloadStringWithRetries(string uri)
    {
        using (var client = new HttpClient())
        {
            var nextDelay = TimeSpan.FromSeconds(1);

            for(int i = 0; i < 3; i++)
            {
                try
                {
                    return await client.GetStringAsync(uri);
                }
                catch
                {
                }

                await Task.Delay(nextDelay);
                nextDelay = nextDelay + nextDelay;
            }
            return await client.GetStringAsync(uri);
        }
    }

    static async Task<string> DownloadStringWithTimeOut(string uri, int timeout)
    {
        using (var client = new HttpClient())
        {
            var downloadTask = client.GetStringAsync(uri);
            var timeoutTask = Task.Delay(timeout);
            var completedTask = await Task.WhenAny(downloadTask, timeoutTask);
            if (timeoutTask  == completedTask)
            {
                return null;
            }
            else
            {
                return await downloadTask;
            }
        }
    }

    static async Task<int> DelayAndReturnAsync(int val)
    {
        await Task.Delay(TimeSpan.FromSeconds(val));
        return val;
    }

    static async Task ProcessTasksAsync()
    {
        var taskA = DelayAndReturnAsync(2);
        var taskB = DelayAndReturnAsync(3);
        var taskC = DelayAndReturnAsync(1);

        var tasks = new[] { taskA, taskB, taskC };
        var stopWatch = Stopwatch.StartNew();
        foreach (var task in tasks)
        {
            var result = await task;
            stopWatch.Stop();
            Console.Out.WriteLine("{0}={1}", stopWatch.Elapsed, result);
            stopWatch.Restart();
        }
    }

    static void Main(string[] args)
    {
        //var result = DownloadStringWithRetries("http://www.baidu.com").Result;
        //Console.Out.WriteLine(result);

        //var result = DownloadStringWithTimeOut("http://www.baidu.com", 10).Result;
        //Console.Out.WriteLine(result == null);

        ProcessTasksAsync().Wait();
    }
}