# Double.NaN Field

[ This article is for Windows Phone 8 developers. If youâ€™re developing for Windows 10, see the latest documentation. ]

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

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

## Syntax

```
Public Const NaN As Double
```

```
public const double NaN
```

## Remarks

The value of this constant is the result of dividing zero by zero.

This constant is returned when the result of an operation is undefined.

Use IsNaN to determine whether a value is not a number. It is not possible to determine whether a value is not a number by comparing it to another value equal to NaN.

## Examples

The following example illustrates the use of NaN:

```
Dim zero As Double = 0
' This condition will return false.
If (0 / zero) = Double.NaN Then
outputBlock.Text &= "0 / 0 can be tested with Double.NaN." & vbCrLf
Else
outputBlock.Text &= "0 / 0 cannot be tested with Double.NaN; use Double.IsNan() instead." & vbCrLf
End If
```

```
Double zero = 0;
// This condition will return false.
if ((0 / zero) == Double.NaN)
{
outputBlock.Text += "0 / 0 can be tested with Double.NaN." + "\n";
}
else
{
outputBlock.Text += "0 / 0 cannot be tested with Double.NaN; use Double.IsNan() instead." + "\n";
}
```

## Version Information

#### Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

## Platforms

Windows Phone