Shortest way of checking if Double is "NaN"

When calling Double.IsNaN() with Double.PositiveInfinity as argument, the result is false. This is against my intuition since infinity is not a number. Apparently "NaN" only exists in terms of a constant in .NET, is this described by the IEEE standard or is it a custom implementation detail? Is there a shorter way to check if a Double is "NaN" than:

(Double.IsNaN(d) || Double.IsPositiveInfinity(d) || Double.IsNegativeInfinity(d))

or

(Double.IsNaN(d) || Double.IsInfinity(d))

As MSDN says, NaN means that result is undefined. With infinities result is defined:

> 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.)

So, it's not good idea to tread infinities as NaN. You can write extension method to check if value is not NaN or infinity:

// Or IsNanOrInfinity
public static bool HasValue(this double value)
{
    return !Double.IsNaN(value) && !Double.IsInfinity(value);
}

You no longer need an extension from SergeyBerezovskiy answer.

double has IsFinite() method to check if a double is a finite number (is not NaN or Infinity):

double.IsFinite(d)

See source code in .Net Framework and .Net Core

There are three special values in the Double type, which is based on IEEE standard 754. One is Positive Infinity, another is Negative Infinity, and the last is Not-a-Number (NaN). All that the Double.IsNaN method does is check to see if the value in the variable is this special NaN value.

If you'd like the value of double to always be a number, you could use this FiniteOrDefault extension. It is of course inspired by Sergey Berezovskiy's answer.

public static bool HasValue(this double value)
{
    return !double.IsNaN(value) && !double.IsInfinity(value);
}

/// <summary>
/// Returns zero when double is NaN or Infinte
/// </summary>
public static double FiniteOrDefault(this double value)
{
    return value.HasValue() ? value : default;
}

With that, code like the following can be much more readable:

Rect dimensions = new Rect
{
    X = Canvas.GetLeft(Control).FiniteOrDefault(),
    Y = Canvas.GetTop(Control).FiniteOrDefault(),
    Width = Control.ActualWidth.FiniteOrDefault(),
    Height = Control.ActualHeight.FiniteOrDefault()
};