Several differences in Book and Codes

[ShervanN]

Hi,

I am not sure but I've seen some differences(or mistakes?)

1. On page 461, The code is written:

private static void ThreadingTimer()
{
void TimeAction(object? o) =>
Console.WriteLine($"System.Threading.Timer {DateTime.Now:T}");
using Timer t1 = new(
TimeAction,
null,
dueTime: TimeSpan.FromSeconds(2),
period: TimeSpan.FromSeconds(3)))
{
Task.Delay(15000).Wait();
}
}

Does the above code have a compiler error?

2. The code in THIS link has:
   await Task.Delay(15000);

But in the book, you wrote:
Task.Delay(15000).Wait();

[christiannagel]

With the book printed code, there are too many curly braces. This should be with the using declaration.

private static void ThreadingTimer()
{
  void TimeAction(object? o) =>
    Console.WriteLine($"System.Threading.Timer {DateTime.Now:T}");

  using Timer t1 = new(
    TimeAction,
    null,
    dueTime: TimeSpan.FromSeconds(2),
    period: TimeSpan.FromSeconds(3));

  Task.Delay(15000).Wait();
}

I've updated updates.md

As an alternative way - with the using statement this could be done:

private static void ThreadingTimer()
{
  void TimeAction(object? o) =>
    Console.WriteLine($"System.Threading.Timer {DateTime.Now:T}");

  using (Timer t1 = new(
    TimeAction,
    null,
    dueTime: TimeSpan.FromSeconds(2),
    period: TimeSpan.FromSeconds(3)))
  {
    Task.Delay(15000).Wait();
  }
}

Before C# 8 only the using statement was possible. See Using, using, using with C# 8 on differences.

With a previous C# version, it was also not possible to use await within the Main method. This is possible now, and the await can also be used with top-level statements. The current version from the book got rid of the method and just uses top-level statements:

static void TimeAction(object? o) =>
    Console.WriteLine($"System.Threading.Timer {DateTime.Now:T}");

using Timer t1 = new(
    TimeAction, 
    null, 
    dueTime: TimeSpan.FromSeconds(2),
    period: TimeSpan.FromSeconds(3));

await Task.Delay(15000);

Remember, the Wait method blocks the calling thread, while with the await the thread is not blocked, but can do something else. With this simple console application it doesn't matter which one to use.

[ShervanN]

Much obliged.