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# Single.NaN Field

.NET Framework 4.6 and 4.5

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

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

## Syntax

```public const float NaN
```

## 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. (But note that dividing a non-zero number by zero returns either PositiveInfinity or NegativeInfinity, depending on the sign of the divisor.)

```float zero = 0.0f;
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.

```float nan1 = Single.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. In general, Single operators cannot be used to compare Single.NaN with other Single values, although comparison methods (such as Equals and CompareTo) can. The following example illustrates the difference in behavior between Single comparison operators and methods.

```using System;

public class Example
{
public static void Main()
{
Console.WriteLine("NaN == NaN: {0}", Single.NaN == Single.NaN);
Console.WriteLine("NaN != NaN: {0}", Single.NaN != Single.NaN);
Console.WriteLine("NaN.Equals(NaN): {0}", Single.NaN.Equals(Single.NaN));
Console.WriteLine("! NaN.Equals(NaN): {0}", ! Single.NaN.Equals(Single.NaN));
Console.WriteLine("IsNaN: {0}", Double.IsNaN(Double.NaN));

Console.WriteLine("\nNaN > NaN: {0}", Single.NaN > Single.NaN);
Console.WriteLine("NaN >= NaN: {0}", Single.NaN >= Single.NaN);
Console.WriteLine("NaN < NaN: {0}", Single.NaN < Single.NaN);
Console.WriteLine("NaN < 100.0: {0}", Single.NaN < 100.0f);
Console.WriteLine("NaN <= 100.0: {0}", Single.NaN <= 100.0f);
Console.WriteLine("NaN >= 100.0: {0}", Single.NaN > 100.0f);
Console.WriteLine("NaN.CompareTo(NaN): {0}", Single.NaN.CompareTo(Single.NaN));
Console.WriteLine("NaN.CompareTo(100.0): {0}", Single.NaN.CompareTo(100.0f));
Console.WriteLine("(100.0).CompareTo(Single.NaN): {0}", (100.0f).CompareTo(Single.NaN));
}
}
// The example displays the following output:
//       NaN == NaN: False
//       NaN != NaN: True
//       NaN.Equals(NaN): True
//       ! NaN.Equals(NaN): False
//       IsNaN: True
//
//       NaN > NaN: False
//       NaN >= NaN: False
//       NaN < NaN: False
//       NaN < 100.0: False
//       NaN <= 100.0: False
//       NaN >= 100.0: False
//       NaN.CompareTo(NaN): 0
//       NaN.CompareTo(100.0): -1
//       (100.0).CompareTo(Single.NaN): 1
```

## Examples

The following example demonstrates the NaN constant.

```Single zero = 0;

// This condition will return false.
if ((0 / zero) == Single.NaN)
{
Console.WriteLine("0 / 0 can be tested with Single.NaN.");
}
else
{
Console.WriteLine("0 / 0 cannot be tested with Single.NaN; use Single.IsNan() instead.");
}
```

## Version Information

#### .NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

#### .NET Framework Client Profile

Supported in: 4, 3.5 SP1

#### XNA Framework

Supported in: 3.0, 2.0, 1.0

#### .NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

#### Portable Class Library

Supported in: Portable Class Library