C# Math.Round double .5 -

i have try math.round class. let see

math.round(2.5) //2.0 math.round(-2.5) //-2.0 math.round(2.5,midpointrounding.toeven) // 2.0 math.round(2.5,midpointrounding.awayfromzero) //3.0 

my simple question if change number -77777777.5 why result -77777778.0 not -77777777.0

math.round(-77777777.5) // -77777778.0 math.round(-77777777.5,midpointrounding.awayfromzero) // -77777778.0 math.round(-77777777.5,midpointrounding.toeven) // -77777778.0 

thanks idea , suggestion.

the default midpointrounding mode toeven. in mode, explained documentation (where a input value),

the integer nearest a. if fractional component of halfway between 2 integers, 1 of , other odd, number returned.

-77777777.5 has 2 nearest integers -77777777 , -77777778 latter 1 1 returned.

in awayfromzero mode, -77777778 further 0 -77777777.