Will my compiler ignore useless code?

Question

I\'ve been through a few questions over the network about this subject but I didn\'t find any answer for my question, or it\'s for another language or it doesn\'t answer totally

Answer 1

I've made a little form to test it according to a few answerers ideas about using long.MaxValue, here's my reference code:

public Form1()
{
    InitializeComponent();
    Stopwatch test = new Stopwatch();
    test.Start();
    myTextBox.Text = test.Elapsed.ToString();
}

and here's the code with kinda useless code:

public Form1()
{
    InitializeComponent();
    Stopwatch test = new Stopwatch();
    test.Start();
    for (int i = 0; i < int.MaxValue; i++)
    {
    }
    myTextBox.Text = test.Elapsed.ToString();
}

You'll remark that I used int.MaxValue instead of long.MaxValue, I didn't want to spend the year day on this one.

As you can see:

---------------------------------------------------------------------
|                   |   Debug               |   Release             |
---------------------------------------------------------------------
|Ref                |   00:00:00.0000019    |   00:00:00.0000019    |
|Useless code       |   00:00:05.3837568    |   00:00:05.2728447    |
---------------------------------------------------------------------

The code isn't optimized. Hang on a bit, I'll try with some int[] to test int[].Lenght:

public Form1()
{
    InitializeComponent();
    int[] myTab = functionThatReturnInts(1);

    Stopwatch test = new Stopwatch();
    test.Start();
    for (int i = 0; i < myTab.Length; i++)
    {

    }
    myTextBox.Text = test.Elapsed.ToString();
}
public int[] functionThatReturnInts(int desiredSize)
{
    return Enumerable.Repeat(42, desiredSize).ToArray();
}

And here's the results:

---------------------------------------------
|   Size            |   Release             |
---------------------------------------------
|             1     |   00:00:00.0000015    |
|           100     |   00:00:00            |
|        10 000     |   00:00:00.0000035    |
|     1 000 000     |   00:00:00.0003236    |
|   100 000 000     |   00:00:00.0312673    |
---------------------------------------------

So even with arrays, it doesn't get optimized at all.