stuck with Convert.ToInt32

[ktomi]

Hi,

Can anyone help me with this? I have no idea what the reason is for this. Apologies in advance if I am missing something obvious or fundamental.

My problem is that the result for Convert.ToInt32(2.5) is 2 and not 3.

I'll post a code snippet and the results it generates in the Output window.

The code:

Print("Calculating Plot positions, i: "+i+", i-Convert.ToInt32((double)i/4): "+(i-Convert.ToInt32((double)i/4)));
Print("Calculating Plot positions, (double)i/4: "+((double)i/4));
Print("Calculating Plot positions, Convert.ToInt32((double)i/4)): "+(Convert.ToInt32((double)i/4)));
Print("Calculating Plot positions, 1.5: "+(1.5));
Print("Calculating Plot positions, Convert.ToInt32(1.5)): "+(Convert.ToInt32(1.5)));
Print("Calculating Plot positions, 2.5: "+(2.5));
Print("Calculating Plot positions, Convert.ToInt32(2.5)): "+(Convert.ToInt32(2.5)));
Print("Calculating Plot positions, 2.51: "+(2.51));
Print("Calculating Plot positions, Convert.ToInt32(2.51)): "+(Convert.ToInt32(2.51)));
Print("Calculating Plot positions, 3.5: "+(3.5));
Print("Calculating Plot positions, Convert.ToInt32(3.5)): "+(Convert.ToInt32(3.5)));


The results in the Output window:

Calculating Plot positions, i: 10, i-Convert.ToInt32((double)i/4): 8
Calculating Plot positions, (double)i/4: 2,5
Calculating Plot positions, Convert.ToInt32((double)i/4)): 2
Calculating Plot positions, 1.5: 1,5
Calculating Plot positions, Convert.ToInt32(1.5)): 2
Calculating Plot positions, 2.5: 2,5
Calculating Plot positions, Convert.ToInt32(2.5)): 2
Calculating Plot positions, 2.51: 2,51
Calculating Plot positions, Convert.ToInt32(2.51)): 3
Calculating Plot positions, 3.5: 3,5
Calculating Plot positions, Convert.ToInt32(3.5)): 4


Thank you in advance.

[Sharad]

Int in general will round down. You can use Math.Ceiling(##.##) to round up.

[ktomi]

No, I don't want to round up. I want to round. And rounding 2.5 is 3, because from 0.5 we round up, that's the rule for the rounding. And in the example it works well for 1.5, 3.5, even 2.51 is rounded up, but not 2.5, and I still don't understand why.

[Sharad]

Implicit Rounding

This was interesting. By default the implicit rounding of int32 will round to the closest EVEN number.

http://msdn.microsoft.com/en-us/library/system.midpointrounding.aspx

[ktomi]

Yes, that link answers the question and it works. Thanks Sharad!