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Math.Round Method (Double, Int32)

 

Rounds a double-precision floating-point value to a specified number of fractional digits.

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

public static double Round(
	double value,
	int digits
)

Parameters

value
Type: System.Double

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

digits
Type: System.Int32

The number of fractional digits in the return value.

Return Value

Type: System.Double

The number nearest to value that contains a number of fractional digits equal to digits.

Exception Condition
ArgumentOutOfRangeException

digits is less than 0 or greater than 15.

System_CAPS_noteNote

For examples and comprehensive usage information about this and other overloads of the Round method, see the Round reference page.

Notes to Callers:

Because of the loss of precision that can result from representing decimal values as floating-point numbers or performing arithmetic operations on floating-point values, in some cases the Round(Double, Int32) method may not appear to round midpoint values to the nearest even value in the digits decimal position. This is illustrated in the following example, where 2.135 is rounded to 2.13 instead of 2.14. This occurs because internally the method multiplies value by 10digits, and the multiplication operation in this case suffers from a loss of precision.

using System;

public class Example
{
   public static void Main()
   {
      double[] values = { 2.125, 2.135, 2.145, 3.125, 3.135, 3.145 };
      foreach (double value in values)
         Console.WriteLine("{0} --> {1}", value, Math.Round(value, 2));

   }
}
// The example displays the following output:
//       2.125 --> 2.12
//       2.135 --> 2.13
//       2.145 --> 2.14
//       3.125 --> 3.12
//       3.135 --> 3.14
//       3.145 --> 3.14

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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