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Visual Studio Code – What is the difference between Console.WriteLine and Console.Out.WriteLineAsync in an async method?

Once, when I used the cw snippet in an async method, Visual Studio would use await Console.Out.WriteLineAsync(); instead of the original Console.WriteLine();. Today I updated Visual Studio to 17.10 and noticed that this feature has been removed.

I would like to ask, is there any difference between these two methods? Or which one is better (besides performance) to use in asynchronous methods?

According to @PanagiotisKanavos’ comments, if a large amount of tasks are used in the code, Console.Out.WriteLineAsync(); is sometimes faster, but in most cases, the performance of both is almost the same.

[Benchmark]
public async ValueTask Benchmark1()
{
    await Parallel.ForAsync(0, 50, async (i, ct) =>
    {
        await Console.Out.WriteLineAsync(LONGTEXT);
        await Job();
        await Console.Out.WriteLineAsync("short_text");
    });
}

[Benchmark]
public async ValueTask Benchmark2()
{
    await Parallel.ForAsync(0, 50, async (i, ct) =>
    {
        Console.WriteLine(LONGTEXT);
        await Job();
        Console.WriteLine("short_text");
    });
}

public async static ValueTask Job()
{
    for (int i = 0; i < 12950; i++)
        await Task.Yield();
}
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2

Answers


  1. 0

    If you look into decompiled source of Console.WriteLine you’ll see

    [MethodImpl(MethodImplOptions.NoInlining)]
public static void WriteLine() => Console.Out.WriteLine();

    So, it’s basically the same.
    Console suports writing into main streams In, Out, Err. I think that Console.WriteLine is just a convient wrapper to write into Out, because it’s most commonly used

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  2. 0

    In terms of performance, the difference is likely negligible because writing text to the console is very fast. Personally, I would say Console.WriteLine should be used over Console.Out.WriteLineAsync.

    I’m not sure whether there is a visible difference between Console.WriteLine and Console.Out.WriteLineAsync.

    The Console.Out property is a static TextWriter that opens the console handle and writes text there. Every Write and WriteAsync method will instead write to the console.

    When you invoke the Console.WriteLine method, it instead invokes Console.Out.WriteLine, and since every Write method in the Console.Out property writes directly to the console, well, it writes a new line to the console.

    However, TextWriter also has .WriteLineAsync methods (aside from other asynchronous write methods). Since anything could inherit from TextWriter, there needs to be a way to write text asynchronously as well. So, Console.Out.WriteLineAsync simply writes text with a new line to the console and is implemented because it’s a part of TextWriter.

    Generally, there is probably no difference, since both write to the console. .WriteLineAsync is implemented because it has to be implemented, since it’s a method that overrides from TextWriter.

    In synchronous and asynchronous methods, I would personally recommend to use Console.WriteLine.

    See TextWriter Methods.

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