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.NET Framework Class Library

Math.Round Method (Double)

Rounds a double-precision floating-point value to the nearest integral value.

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
Public Shared Function Round ( _
	a As Double _
) As Double

Parameters

a
Type: System.Double

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

Return Value

Type: System.Double
The integer nearest a. If the fractional component of a is halfway between two integers, one of which is even and the other odd, then the even number is returned. Note that this method returns a Double instead of an integral type.
Note Note

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) 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.

Module Example
   Public Sub Main()
      Dim value As Double = 11.1
      For ctr As Integer = 0 To 5    
         value = RoundValueAndAdd(value)
      Next
      Console.WriteLine()

      value = 11.5
      RoundValueAndAdd(value)
   End Sub 

   Private Function RoundValueAndAdd(value As Double) As Double
      Console.WriteLine("{0} --> {1}", value, Math.Round(value))
      Return value + .1
   End Function    
End Module 
' 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

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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