Use
double.IsNaN() to check if a double is NaN CS-W1003
Bug risk
Critical
8 months ago
—
8 months old
Comparison with
NaN always evaluates to false19 var pi = 3.14;
20 // CS-W1003: Invalid comparison against `NaN`.
21 // https://deepsource.io/directory/analyzers/csharp/issues/CS-W1003
22 var isNaN = pi == double.NaN;23
24 // CS-W1025: Potential memory leak inside `for` loop due to `stackalloc`.
25 // https://deepsource.io/directory/analyzers/csharp/issues/CS-W1025.
Description
By specification, NaN is not equal to anything, not even itself. Therefore, comparing any double with NaN will always evaluate to false. The preferred and right approach is to directly use the double's .isNaN method.
Bad practice
var d = double.NaN;
d == Double.NaN; // evaluates to false
Recommended
var d = double.NaN;
double.IsNaN(d); // evaluates to true