Math.Round returning a rounded up for odd values but rounds down for even

Question

I am trying to found a float using math round I found the following

0.5 --> 0
1.5 --> 2
2.5 --> 2
3.5 --> 4

and so on. I believ

Answer 1

You may try like this

 Math.Round(value, MidpointRounding.AwayFromZero);

From MSDN

If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned.

Also to mention one important point which I think is good to mention is that Microsoft has followed the IEEE 754 standard. This is also mentioned in MSDN for Math.Round under Remarks which says:

Round to nearest, ties to even – rounds to the nearest value; if the number falls midway it is rounded to the nearest value with an even (zero) least significant bit, which occurs 50% of the time; this is the default for binary floating-point and the recommended default for decimal.

Round to nearest, ties away from zero – rounds to the nearest value; if the number falls midway it is rounded to the nearest value above (for positive numbers) or below (for negative numbers); this is intended as an option for decimal floating point.

Answer 2

You could use this one, to overcome that you have stated:

Math.Round(value, MidpointRounding.AwayFromZero);

Using the above:

When a number is halfway between two others, it is rounded toward the nearest number that is away from zero.

For further documentation about the MidpointRounding enumeration, please have a look here.

Answer 3

From documentation;

The integer nearest a. If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned. Note that this method returns a Double instead of an integral type.

Math.Round method has some overloads that takes MidpointRounding as a parameter which you can specify the rounding value if it is midway between two numbers.

AwayFromZero 

When a number is halfway between two others, it is rounded toward the nearest number that is away from zero.

ToEven

When a number is halfway between two others, it is rounded toward the nearest even number.

Answer 4

This is known as bankers rounding (round to even). You can read more about it here. This is a .NET Framework feature and is working as designed.