# Double.IsNaN() Method in C#

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.

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