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# Double.IsNaN Method

.NET Framework 1.1

Returns a value indicating whether the specified number evaluates to a value that is not a number (NaN).

```[Visual Basic]
Public Shared Function IsNaN( _
ByVal d As Double _
) As Boolean
[C#]
public static bool IsNaN(
double d
);
[C++]
public: static bool IsNaN(
double d
);
[JScript]
public static function IsNaN(
d : double
) : Boolean;```

#### Parameters

d
A double-precision floating point number.

#### Return Value

true if d evaluates to NaN; otherwise, false.

#### Remarks

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

#### Example

[Visual Basic, C#, C++] The following code sample illustrates the use of IsNaN:

```[Visual Basic]
' 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

[C#]
// This will return true.
if (Double.IsNaN(0 / zero))
{
Console.WriteLine("Double.IsNan() can determine whether a value is not-a-number.");
}

[C++]
// This will return true.
if (Double::IsNaN(0 / zero)) {
Console::WriteLine(S"Double::IsNan() can determine whether a value is not-a-number.");
}
```

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button in the upper-left corner of the page.

#### Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard