Math.Round function by aliasgar

February 1, 2010 muthu C# Miscellaneous 0

I had the below problem with the Math.Round() function:

Problem :

  When I use the Math.Round Function it uses the Bankers Method. (ie., Round(5.5) = 5 and Round(5.50001) = 6). But when I use the Format String  “{0:F0}” it uses the proper Mathematical Method.(ie. Round(5.5)=6). Why this inconsistency followed in .NET?

 

    Is any other way to switch the Math.Round function from Bankers Method to Mathematical Method?  or  Is any other way to switch the Format String “{0:F0}” from Mathematical Method to Bankers Method?

Solution:

   I had to write my own function. The built-in Round function uses banker’s rounding to round to the nearest EVEN digit when the LSD is a 5. Here is one solution to always rounding up when the least significant digit is a 5:

static void Main(string[] args)
{

double num; int place; string snum;

Console.Write(“Enter positive or negative number to round: “);

snum = Console.ReadLine();

if (snum == “”) snum = “0”;

num = Convert.ToDouble(snum);

Console.Write(“Number of places to round right or left (-) of decimal: “);

snum = Console.ReadLine();

if (snum == “”) snum = “0”;

place = Convert.ToInt32(snum);

Console.WriteLine(“nThe rounded number is {0}”, roundnum(num, place));

Console.WriteLine();

}

public static double roundnum(double num, int place)
{

double n;

n = num * Math.Pow(10, place);

n = Math.Sign(n) * Math.Abs(Math.Floor(n + .5));

return n / Math.Pow(10, place);

}