# Double.IsNaN(Double) Method

## Definition

Returns a value that indicates whether the specified value is not a number (NaN).

``````public:
static bool IsNaN(double d);``````
``````public:
static bool IsNaN(double d) = System::Numerics::INumberBase<double>::IsNaN;``````
``public static bool IsNaN (double d);``
``static member IsNaN : double -> bool``
``Public Shared Function IsNaN (d As Double) As Boolean``

#### Parameters

d
Double

A double-precision floating-point number.

#### Returns

Boolean

`true` if `d` evaluates to NaN; otherwise, `false`.

## Examples

The following code example illustrates the use of IsNaN:

``````// This will return true.
if ( Double::IsNaN( 0 / zero ) )
{
Console::WriteLine( "Double::IsNan() can determine whether a value is not-a-number." );
}
``````
``````// This will return true.
if (Double.IsNaN(0 / zero))
Console.WriteLine("Double.IsNan() can determine whether a value is not-a-number.");
``````
``````// This will return true.
if Double.IsNaN(0. / zero) then
printfn "Double.IsNan() can determine whether a value is not-a-number."
``````
``````' This will return true.
If Double.IsNaN(0 / zero) Then
Console.WriteLine("Double.IsNan() can determine whether a value is not-a-number.")
End If
``````

## Remarks

Floating-point operations return NaN to signal that result of the operation is undefined. For example, dividing 0.0 by 0.0 results in NaN.

Note

IsNaN returns `false` if a Double value is either PositiveInfinity or NegativeInfinity. To test for these values, use the IsInfinity, IsPositiveInfinity, and IsNegativeInfinity methods.