When is DivideByZeroException thrown?

What a strange question most developers will say. DivideByZeroException is thrown every time you divide by zero, right? No – it depends.

Let’s try – regular division with integers.

int i1 = 4;
int i2 = 0;

try
{
Console.WriteLine(i1 / i2);

}
catch (System.DivideByZeroException)
{
Console.WriteLine("DivideByZeroException");
}

Hmm, I see a DivideByZeroException coming, and that’s absolutely correct. So what is all the fuzz about?

Let’s try again, but this time with floating point numbers.

double d1 = 4.0;
double d2 = 0.0;

try
{
Console.WriteLine(d1 / d2);

}
catch (System.DivideByZeroException)
{
Console.WriteLine("DivideByZeroException");
}

If you try to run this piece of code, no exception is thrown. Instead INF (short for infinite) is returned. To be more precise a PositiveInfinity, due to the decimalNumerator is positive.

I read this somewhere and had to test it. I even asked my colleagues when DivideByZeroException is thrown and showed them these code examples. None of them knew the right answer. So it’s not only me, whom is ignorant. 🙂