Math.Round () function problem in C #

Math.Round () There is a problem when rounding:
Math.Round (2.5,0) = 2;
Math.Round (3.5,0) = 4;

2.5 should be equal to 3.

This problem also exists in ASP, but there is also a formatnumber in ASP, but still do not know how to use.

Explain:

Math.Round () to be exact, this function is not rounded, but four homes six into the five, that is less than 4 or greater than 6 of the house is not disputed, and 5 is in the middle, if rounding will cause the overall deviation of the data, so the principle is: if the rounding bit is 5, Then the last one after rounding is an even number, which is international practice.

Now do the project to 5 into, the solution:

The current practice is:
For example: (3.45*10+0.5) rounding, then divided by 10