# Double.IsNaN() Method in C#

• Last Updated : 13 Feb, 2019

In C#, Double.IsNaN() is a Double struct method. This method is used to check whether the specified value is not a number (NaN).

Syntax: public static bool IsNaN (double d);

Parameter:
d: It is a double-precision floating-point number of type System.Double

Return Type: This function returns a Boolean value i.e. True, if specified value is not a number(NaN), otherwise returns False.

Example:

```Input  : d = 0.0 / 0.0
Output : True

Input  : d = 1.734
Output : False
```

Code: To demonstrate the Double.IsNaN(Double) method.

 `// C# code to demonstrate ``// Double.IsNaN(Double) method ``using` `System;`` ` `class` `GFG { ``     ` `    ``// Main Method``    ``public` `static` `void` `Main(String[] args) ``    ``{ `` ` `        ``// first example ``        ``Double f1 = 1.0 / 0.0; `` ` `        ``bool` `res = Double.IsNaN(f1); `` ` `        ``// printing the output ``        ``if` `(res) ``            ``Console.WriteLine(f1 + ``" is NaN"``); ``        ``else``            ``Console.WriteLine(f1 + ``" is not NaN"``); `` ` `        ``// second example ``        ``double` `f2 = 0.0 / 0.0; `` ` `        ``bool` `res1 = Double.IsNaN(f2); `` ` `        ``// printing the output ``        ``if` `(res1) ``            ``Console.WriteLine(f2 + ``" is NaN"``); ``        ``else``            ``Console.WriteLine(f2 + ``" is not NaN"``); ``    ``} ``} `
Output:
```Infinity is not NaN
NaN is NaN
```

Note:

• If we divide any value by 0 directly, the Compiler will show an error. So, in the above example, 0 is stored in a variable first.
• Every floating point operation returns a NaN to show that the result of the operation is undefined.
My Personal Notes arrow_drop_up