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# Double.NaN Field

Visual Studio 2010

Updated: March 2012

Represents a value that is not a number (NaN). This field is constant.

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

## Syntax

```'Declaration
Public Const NaN As Double
```

## Remarks

A method or operator returns NaN when the result of an operation is undefined. For example, the result of dividing zero by zero is NaN, as the following example shows.

```
Dim zero As Double = 0
Console.WriteLine("{0} / {1} = {2}", zero, zero, zero/zero)
' The example displays the following output:
'         0 / 0 = NaN

```

In addition, a method call with a NaN value or an operation on a NaN value returns NaN, as the following example shows.

```
Dim nan1 As Double = Double.NaN

Console.WriteLine("{0} + {1} = {2}", 3, nan1, 3 + nan1)
Console.WriteLine("Abs({0}) = {1}", nan1, Math.Abs(nan1))
' The example displays the following output:
'       3 + NaN = NaN
'       Abs(NaN) = NaN

```

Use the IsNaN method to determine whether a value is not a number. Two NaN values are considered unequal to one another. Therefore, it is not possible to determine whether a value is not a number by using the quality operator to compare it to another value that is equal to NaN. The comparison returns false, as the following example shows.

```
Dim result As Double = Double.Nan
Console.WriteLine("{0} = Double.Nan: {1}",
result, result = Double.Nan)
' The example displays the following output:
'         NaN = Double.Nan: False

```

## Examples

The following code example illustrates the use of NaN:

```
Dim zero As Double = 0

' This condition will return false.
If (0 / zero) = Double.NaN Then
Console.WriteLine("0 / 0 can be tested with Double.NaN.")
Else
Console.WriteLine("0 / 0 cannot be tested with Double.NaN; use Double.IsNan() instead.")
End If

```

## Version Information

#### .NET Framework

Supported in: 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

## Platforms

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

## Change History

Date

History

Reason

March 2012

Revised the Remarks section.

Information enhancement.

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