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Math.Round Method (Double, MidpointRounding)

 

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 numbers.

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

public static double Round(
	double value,
	MidpointRounding mode
)

Parameters

value
Type: System.Double

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

mode
Type: System.MidpointRounding

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

Return Value

Type: System.Double

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.

Exception Condition
ArgumentException

mode is not a valid value of System.MidpointRounding.

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, MidpointRounding) method may not appear to round midpoint values to the nearest even integer. In the following example, because the floating-point value .1 has no finite binary representation, the first call to the Round(Double) method with a value of 11.5 returns 11 instead of 12.

using System;

public class Example
{
   public static void Main()
   {
      double value = 11.1;
      for (int ctr = 0; ctr <= 5; ctr++)    
         value = RoundValueAndAdd(value);

      Console.WriteLine();

      value = 11.5;
      RoundValueAndAdd(value);
   }

   private static double RoundValueAndAdd(double value)
   {
      Console.WriteLine("{0} --> {1}", value, Math.Round(value, 
                        MidpointRounding.AwayFromZero));
      return value + .1;
   }
}
// The example displays the following output:
//       11.1 --> 11
//       11.2 --> 11
//       11.3 --> 11
//       11.4 --> 11
//       11.5 --> 11
//       11.6 --> 12
//       
//       11.5 --> 12

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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