double.Parse(do uble.MaxValue.T oString()) yields an Exception

[Markus Kling]

"double.Parse(d ouble.MaxValue. ToString())" yields the following Exception:

Value was either too large or too small for a Double.
at System.Number.P arseDouble(Stri ng value, NumberStyles options,
NumberFormat
Info numfmt)
at System.Double.P arse(String s, NumberStyles style, NumberFormatInf o info)
at System.Double.P arse(String s)
...

Even double.Parse((d ouble.MaxValue -1).ToString()) states the same error
message.

That's completly illogical. Is this an error or my misunderstandin g?

[Julijan Sribar]

Hello,

Problem is caused by rounding in the default implementation of ToString
method. In the example you gave, method creates a string presentation of a
number rounded to a value that is larger than the largest double number
allowed. So, when you try to parse that string, it throws an exception. You
can check this comparing following two outputs:

Console.WriteLi ne(double.MaxVa lue.ToString()) ;
Console.WriteLi ne(double.MaxVa lue.ToString("E 20"));

Therefore this code:

double.Parse(do uble.MaxValue.T oString("E20"))

will not throw the exception.

Regards,

Julijan
"Markus Kling" <Ma*********@di scussions.micro soft.com> wrote in message
news:26******** *************** ***********@mic rosoft.com...

"double.Parse(d ouble.MaxValue. ToString())" yields the following Exception:

Value was either too large or too small for a Double.
at System.Number.P arseDouble(Stri ng value, NumberStyles options,
NumberFormat
Info numfmt)
at System.Double.P arse(String s, NumberStyles style, NumberFormatInf o info) at System.Double.P arse(String s)
...

Even double.Parse((d ouble.MaxValue -1).ToString()) states the same error
message.

That's completly illogical. Is this an error or my misunderstandin g?

[Jon Skeet [C# MVP]]

Julijan Sribar wrote:

Problem is caused by rounding in the default implementation of ToString
method. In the example you gave, method creates a string presentation of a
number rounded to a value that is larger than the largest double number
allowed. So, when you try to parse that string, it throws an exception. You
can check this comparing following two outputs:

Console.WriteLi ne(double.MaxVa lue.ToString()) ;
Console.WriteLi ne(double.MaxVa lue.ToString("E 20"));

An alternative format specified to use is "R", which is the round-trip
specifier - it always preserves enough information to complete the
format/parse cycle.

Jon

[Markus Kling]

Sure, that was it. I should drink more coffee.
Thanks a bunch ;)

[Markus Kling]

Just for completion. The recoverable format is not really recoverable. It
does NOT preseve the milliseconds. You have to serialize the DateTime
(timestamp) as long if you want to preserve them.

Markus
"Jon Skeet [C# MVP]" <sk***@pobox.co m> schrieb im Newsbeitrag
news:11******** *************@g 49g2000cwa.goog legroups.com...

Julijan Sribar wrote:

Problem is caused by rounding in the default implementation of ToString
method. In the example you gave, method creates a string presentation of
a
number rounded to a value that is larger than the largest double number
allowed. So, when you try to parse that string, it throws an exception.
You
can check this comparing following two outputs:

Console.WriteLi ne(double.MaxVa lue.ToString()) ;
Console.WriteLi ne(double.MaxVa lue.ToString("E 20"));

An alternative format specified to use is "R", which is the round-trip
specifier - it always preserves enough information to complete the
format/parse cycle.

Jon

[Jon Skeet [C# MVP]]

Markus Kling <ma**********@n ospam.nospam> wrote:

Just for completion. The recoverable format is not really recoverable. It
does NOT preseve the milliseconds. You have to serialize the DateTime
(timestamp) as long if you want to preserve them.

The round-trip specifier is a *numeric* specifier. "R" for DateTime
means RFC1123.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet Blog: http://www.msmvps.com/jon.skeet
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