How can I compare a float to NaN if comparisons to NaN always return false?

user_76939 0
Viewed 40477

I have a float value set to NaN (seen in the Watch Window), but I can't figure out how to detect that in code:

if (fValue == float.NaN) // returns false even though fValue is NaN
{
}
c#
5 Answers

You want float.IsNaN(...). Comparisons to NaN always return false, no matter what the value of the float is. It's one of the quirks of floating points.

That means you can do this:

if (f1 != f1) { // This conditional will be true if f1 is NaN.

In fact, that's exactly how IsNaN() works.

user_751700

Try this:

if (float.IsNaN(fValue))
{
}
t4rzsan_641610 
if(float.isNaN(fValue))
{
}
Jeff_Mc_255210
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