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# Double.NaN Field

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

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

## Syntax

```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:

```
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

Windows Phone