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Convert.ToDouble with negative number on OS X

Posted on 2011-09-19
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Last Modified: 2012-08-14
Hi,

In our Silverlight applicaiton when we uses Convert.ToDouble("-1") on an OS X (10.7) it crashes with:
"Unhandled Error in Silverlight 4 Application [Format_InvalidString]"

Any negative values will crash.

Even if we run a virtual Windows on the mac it will crash with the same error message. On a clean Windows machine it works fine.

Any help appreciated.
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Question by:xlmaster200
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Expert Comment

by:nishant joshi
ID: 36559281
try to cast if convert not works well.

(Double)"-1";
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Expert Comment

by:Easwaran Paramasivam
ID: 36559282
Avoid exception using TryParse method.

if(Double.TryParse("-1") != null )
   Convert.ToDouble("-1");

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Expert Comment

by:Easwaran Paramasivam
ID: 36559291
Try to use Double.Parse("-1") then.

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by:xlmaster200
ID: 36559506
I could try to cast it but I'd really liked to now if anyone can explain why it's not working, is it a bug in the runtime?


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smickle earned 500 total points
ID: 36565299
I've had similar issues in the past. May not even be isolated to the Mac, but in my case it was the default Culture of the machine that was making stuff explode.

By default, .NET will use the default culture of the machine that is spinning up the runtime, unless you explicity specify which culture to use in your code or configurations. In order for the runtime to know "how" to convert something from some string to a typed double, it uses a format string to determine the conversion pattern.

I ended up having to do stuff like this:
 
// use InvariantCulture
var someDouble = Double.Parse("1234.0",CultureInfo.InvariantCulture);

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By using InvariantCulture, the runtime didn't have to use the machine's default culture and possibly change it's conversion pattern. In my code snipped above, the dot in 1234.0 was getting interpretted as a thousands separator in a different culture. So I got the weird FormatException.

This is just a guess as a possibility of why it is happening.

In my case, I was pulling my hair out thinking is was something to do with the difference between a 32-bit system and a 64-bit system. It was just coincidental that the OS's were different, so that lead me down way too many wrong turns to a solution.

Hope this helps.

-Steve
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Author Comment

by:xlmaster200
ID: 36565904
Thanks for your answer Steve.
So in other words I can't use Convert.ToDouble (or Convert.ToInt16) anywhere in the code...
I did some test on the client side for a Mac:
string s = "-1";
double d =Convert.ToDouble(s)   - Unhandled Error in Silverlight 4 Application [Format_InvalidString]
double d = Double.Parse(s)  - Unhandled Error in Silverlight 4 Application [Format_InvalidString]
double d = Double.Parse(s,CultureInfo.InvariantCulture) - OK

What culture does not accept "-" before a number? If I try cdbl("-1") in a VBA macro on the Mac it works OK.

It feels no good to change Convert.ToDouble everywhere in the code.
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Author Comment

by:xlmaster200
ID: 36566598
I printed out CultureInfo.CurrentCulture.NumberFormat.NegativeSign and found that on the Mac the NegativeSign was a little longer than in Windows... Silly me not thinking of that...

So I go with your suggestion Steve and use InvariantCulture on the client side
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by:smickle
ID: 36570840
Ha, extra long negative sign. That's great.

You might be able to get around changing all the code, and you can explicitly set your desired culture in web.config, if this is an asp.net app. Not sure if this will work off the top of my head, but it could. This would ensure that all your conversions in your code that run within your web app will use a preset culture.

 
<!-- system.web section inside your web.config -->
<globalization culture="en-US"/>

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Globalization can be a headache in many sneaky ways though. Especially if you have values stored and retrieved from SQL Server for example. And the SQL Server has a different culture setting than the code that uses it. They must match in order to get predictable results. DateTime formats and conversions are the main ones that get hosed in that scenario due to the different order of the mm/dd/yy structure.
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