Why Convert.ToInt32 Might be Dangerous

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Why Convert.ToInt32 Might be Dangerous

published 3 months, 23 days ago, submitted by shaharab 3 months, 23 days ago

devmuse.com — Casting float to int is interesting. Not only it causes the value to get truncated, but it also changes binary representation. When you want to cast float to int you have two options:

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Comments:

I wouldn't say it's dangerous per se, but it's definitely interesting. I would have never expected Convert.ToInt32 would actually perform a rounding operation.

posted by

RPenton 3 months, 23 days ago

I believe this is because it uses the round to even method (http://en.wikipedia.org/wiki/Rounding#Round-to-even_method)

posted by

johnrummell 3 months, 22 days ago

You are right jrummell, as written in the link that you provided this is called “bankers’ rounding”.
I understand why banks need this behaviour (to be fair), what i can’t understand is why should we have this unexpected behaviour in the .Net framework.

posted by shaharyr 3 months, 22 days ago

More detail on the surprising way default rounding works in .NET - http://www.dotnetkicks.com/csharp/Banker_s_Rounding_vs_Common_Rounding_in_NET

posted by

powerrush 3 months, 22 days ago

Another potential gotcha when using nullables: Convert.ToInt32(x) returns zero when x==null. Same for ToInt64(), ToSingle(), etc.

posted by chinhdo 3 months, 18 days ago