Question

I have the following code:

int a = Convert.ToInt32(4.5m);
int b = Convert.ToInt32(5.5m);

Console.WriteLine(a);
Console.WriteLine(b);

And here’s the output:

4
6

Why does Convert.ToInt32 rounds decimal values to the nearest even number?

Answer 1

Convert is using rounding to nearest, or banker’s rounding:

The behavior of this method follows IEEE Standard 754, section 4. This
kind of rounding is sometimes called rounding to nearest, or banker’s
rounding. It minimizes rounding errors that result from consistently
rounding a midpoint value in a single direction.

To control the type of rounding used by the Round method, call the
Math.Round(Double, MidpointRounding) overload.