# Math.Round Method (Double, MidpointRounding)

.NET Framework 2.0

Note: This method is new in the .NET Framework version 2.0.

Rounds a double-precision floating-point value to the nearest integer. A parameter specifies how to round the value if it is midway between two other numbers.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

## Syntax

public static double Round (
double value,
MidpointRounding mode
)
public static double Round (
double value,
MidpointRounding mode
)
public static function Round (
value : double,
mode : MidpointRounding
) : double

#### Parameters

value

A double-precision floating-point number to be rounded.

mode

Specification for how to round value if it is midway between two other numbers.

#### Return Value

The integer nearest value. If value is halfway between two integers, one of which is even and the other odd, then mode determines which of the two is returned.

## Exceptions

Exception typeCondition

ArgumentException

mode is not a valid value of System.MidpointRounding.

## Remarks

The behavior of this method follows IEEE Standard 754, section 4. The kind of rounding that is performed if mode is ToEven is sometimes called rounding to nearest, or banker's rounding.

## Example

The following code example demonstrates the Round method in conjunction with the MidpointRounding enumeration. Although the code example rounds decimal numbers, the Round method rounds double-precision floating-point numbers in a similar way.

// This example demonstrates the Math.Round() method in conjunction
// with the MidpointRounding enumeration.
using System;

class Sample
{
public static void Main()
{
decimal result = 0.0m;
decimal posValue =  3.45m;
decimal negValue = -3.45m;

// By default, round a positive and a negative value to the nearest even number.
// The precision of the result is 1 decimal place.

result = Math.Round(posValue, 1);
Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, posValue);
result = Math.Round(negValue, 1);
Console.WriteLine("{0,4} = Math.Round({1,5}, 1)", result, negValue);
Console.WriteLine();

// Round a positive value to the nearest even number, then to the nearest number away from zero.
// The precision of the result is 1 decimal place.

result = Math.Round(posValue, 1, MidpointRounding.ToEven);
Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", result, posValue);
result = Math.Round(posValue, 1, MidpointRounding.AwayFromZero);
Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", result, posValue);
Console.WriteLine();

// Round a negative value to the nearest even number, then to the nearest number away from zero.
// The precision of the result is 1 decimal place.

result = Math.Round(negValue, 1, MidpointRounding.ToEven);
Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.ToEven)", result, negValue);
result = Math.Round(negValue, 1, MidpointRounding.AwayFromZero);
Console.WriteLine("{0,4} = Math.Round({1,5}, 1, MidpointRounding.AwayFromZero)", result, negValue);
Console.WriteLine();
}
}
/*
This code example produces the following results:

3.4 = Math.Round( 3.45, 1)
-3.4 = Math.Round(-3.45, 1)

3.4 = Math.Round( 3.45, 1, MidpointRounding.ToEven)
3.5 = Math.Round( 3.45, 1, MidpointRounding.AwayFromZero)

-3.4 = Math.Round(-3.45, 1, MidpointRounding.ToEven)
-3.5 = Math.Round(-3.45, 1, MidpointRounding.AwayFromZero)

*/

## Platforms

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

## Version Information

#### .NET Framework

Supported in: 2.0