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.NET Forum / Languages / C# / June 2007Casting to double in C#
Hi guys, I am having a problem with the following code snippet:- double x = (myReader["TimeStamp"]); double y = (myReader["YAxis"]); Resulting in the follwing compilation error: Cannot implicitly convert type 'object' to 'double'. An explicit conversion exists (are you missing a cast?) To fix this I modified the code to :- double x = (double)(myReader["TimeStamp"]); double y = (double)(myReader["YAxis"]); with this there are no compilation errors but I get a runtime exception saying :- System.InvalidCastException: specified cast is not valid. Any clues on how to fix this will be much appreciated. On Jun 8, 3:52 pm, kanepa...@hotmail.com wrote: > Hi guys, I am having a problem with the following code snippet:- > [quoted text clipped - 17 lines] > > Any clues on how to fix this will be much appreciated. Yes - the cast is trying to unbox. It's probably in a different format, eg decimal. Print out myReader["TimeStamp"].GetType() and put an appropriate cast in before the double, eg: double x = (double)(decimla)(myReader["TimeStamp"]); Jon Well , I tried what you said and it turns out that the type is string and it doesnt allow conversions from string to double. > On Jun 8, 3:52 pm, kanepa...@hotmail.com wrote: > [quoted text clipped - 30 lines] > > - Show quoted text - > Well , I tried what you said and it turns out that the type is string > and it doesnt allow conversions from string to double. If you know it's a string, then you can use double.Parse() to convert to double. On Jun 8, 10:31 pm, "Peter Duniho" <NpOeStPe...@nnowslpianmk.com> wrote: > > Well , I tried what you said and it turns out that the type is string > > and it doesnt allow conversions from string to double. > > If you know it's a string, then you can use double.Parse() to convert to > double. Yeah now it's clear - difference between casting and converting. That's why we don't have InvalidCastException for Convert.ToXXXX() method. Thank you Jon for the clarification. double y = double.Parse((string)myReader["YAxis"]); What happens if you try double x = Convert.ToDouble(myReader["TimeStamp"]); ??? Cheers, Johnny J. > Hi guys, I am having a problem with the following code snippet:- > [quoted text clipped - 17 lines] > > Any clues on how to fix this will be much appreciated. yea that worked. thanks for the help guys On Jun 8, 11:18 am, "Johnny J?rgensen" <j...@altcom.se> wrote: > What happens if you try > [quoted text clipped - 32 lines] > > - Show quoted text - Double.TryParse can be more useful... Great. MS is recommending using direct casting (double) instead of Convert, but often Convert will do the job where the direct casting fails (for some reason I don't know) Cheers, Johnny J. yea that worked. thanks for the help guys On Jun 8, 11:18 am, "Johnny Jörgensen" <j...@altcom.se> wrote: > What happens if you try > [quoted text clipped - 33 lines] > > - Show quoted text - On Jun 8, 4:31 pm, "Johnny J?rgensen" <j...@altcom.se> wrote: > MS is recommending using direct casting (double) instead of Convert, but > often Convert will do the job where the direct casting fails (for some > reason I don't know) The reason in this case is simple - you can't cast from a string to a double, but you can convert from a string to a double. Jon On Jun 8, 8:18 pm, "Johnny J?rgensen" <j...@altcom.se> wrote: > What happens if you try > [quoted text clipped - 32 lines] > > - Show quoted text - try { double x = Double.Parse(myReader["TimeStamp"]); } catch(....)/Handle exception here. If the string contains data that cannot be parsed to double it would throw exception.) { .......... .......... } On Jun 8, 8:30 pm, "Aneesh Pulukkul[MCSD.Net]" <anees...@gmail.com> wrote: > On Jun 8, 8:18 pm, "Johnny J?rgensen" <j...@altcom.se> wrote: > [quoted text clipped - 50 lines] > > - Show quoted text - It seems Double.Parse accepts string parameters only. Since this is an object, Convert.ToDouble is the apt one. On Jun 8, 8:30 pm, "Aneesh Pulukkul[MCSD.Net]" <anees...@gmail.com> wrote: > On Jun 8, 8:18 pm, "Johnny J?rgensen" <j...@altcom.se> wrote: > [quoted text clipped - 50 lines] > > - Show quoted text - Or you can convert the value to string and then parse - better avoid two conversions. On Jun 8, 8:30 pm, "Aneesh Pulukkul[MCSD.Net]" <anees...@gmail.com> wrote: > On Jun 8, 8:18 pm, "Johnny Jörgensen" <j...@altcom.se> wrote: > [quoted text clipped - 54 lines] >Or you can convert the value to string and then parse - better avoid >two conversions. Cast, not convert, the object to string. There would be only one conversion, and an explicit cast should be far more efficient than calling Convert.ToDouble(object) and having a dynamic type check. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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