Round Method (Decimal, Int32, MidpointRounding)

Math.Round Method (Decimal, Int32, MidpointRounding)

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

Rounds a decimal value to a specified precision. A parameter specifies how to round the value if it is midway between two other numbers.

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

public static decimal Round (
	decimal d,
	int decimals,
	MidpointRounding mode
)
public static Decimal Round (
	Decimal d, 
	int decimals, 
	MidpointRounding mode
)
public static function Round (
	d : decimal, 
	decimals : int, 
	mode : MidpointRounding
) : decimal

Parameters

d

A decimal number to be rounded.

decimals

The number of significant decimal places (precision) in the return value.

mode

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

Return Value

The number nearest d with a precision equal to decimals. If d is halfway between two numbers, one of which is even and the other odd, then mode determines which of the two numbers is returned. If the precision of d is less than decimals, then d is returned unchanged.

Exception typeCondition

ArgumentOutOfRangeException

decimals is less than 0 or greater than 28.

ArgumentException

mode is not a valid value of System.MidpointRounding.

OverflowException

The result is outside the range of a Decimal.

The decimals parameter specifies the number of significant decimal places in the return value and ranges from 0 to 28. If decimals is zero, an integer is returned.

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.

The following code example demonstrates the Round method in conjunction with the MidpointRounding enumeration.

// 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)

*/

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.

.NET Framework

Supported in: 2.0

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