Nullable double NaN comparison in C#

Question

I have 2 nullable doubles, an expected value and an actual value (let\'s call them value and valueExpected). A percentage is found using 100 * (value / valueExpected). Howev

Answer 1

You can also use

if (!Double.IsNaN(myDouble ?? 0.0))

The value in the inner-most parenthesis is either the myDouble (with its Nullable<> wrapping removed) if that is non-null, or just 0.0 if myDouble is null. Se ?? Operator (C#).

Answer 2

With C# 7.0 Pattern matching combined null + NaN check check can be written like this:

double? d = whatever;
if(d is double val && double.IsNaN(val))
   Console.WriteLine(val);

The advantage is local scoped variable val at hand, which is not null, nor double.NaN and can even be used outside of if.

Answer 3

With all Nullable<T> instances, you first check the bool HasValue property, and then you can access the T Value property.

double? d = 0.0;        // Shorthand for Nullable<double>
if (d.HasValue && !Double.IsNaN(d.Value)) {
    double val = d.Value;

    // val is a non-null, non-NaN double.
}

Answer 4

I had the same issue and I solved it with casting the double? with double

double.IsNaN((double)myDouble)

this will return true if NaN and false if not