I have float number in string. there is one problem. Number uses "." not "," as decimal point.
This code is not working:
MyNumber = float.Parse("123.5");
I know that I can use string replace function to "repair" this string before Parsing.
MyNumber = float.Parse("123.5".Replace('.',',');
But is there any other way to do it?
Using string replace is very fragile, and will lead to suttle bugs. Specify the IFormatProvider instead. For instance:
MyNumber = float.Parse("123.5", CultureInfo.InvariantCulture);
Or you can specify the NumberFormatInfo using another overload of Parse.
To add to Steven's question, rather than argue differently, the important thing is why the decimal separator is ..
If it's because the source is in a computer-readable format where the period decimal separator is specified as part of the document specification, then I'd go precisely as Steven does in using CultureInfo.InvariantCulture.
If it's human input in a particular locale, then you would want to match that locale by the CultureInfo appropriate for that locale, otherwise if the software is used with a different locale you'd have precisely the opposite problem. Generally you would want to set the thread's CurrentCulture to match this (CurrentCulture for formats, CurrentUICulture for languages). If you've done this, then you don't need to pass a culture at all, as the form float.Parse(string) uses that culture - however, you may wish to use float.Parse(string, CurrentCulture) to be explicit that this is what you are doing (and to shut up some software analysis that complains when you aren't specific in this way).
What gets really tricky, is if you potentially have to accept both period and comma - not least because many cultures that use period as a decimal separator, use comma as a thousands separator, and ultimately it's impossible to guarantee unambiguous parsing. However, assuming the thousands issue doesn't affect you, then the code you gave in your question is the approach, though I'd recommend doing the opposite (replace comma with period) and then parsing with the invariant culture, as that removes any further complications caused by yet more culture changes.
It depends on current culture of currently executed thread culture.
float.Parse("123,5", system.threading.thread.currentthread.currentculture);
float.Parse("123.5", system.threading.thread.currentthread.currentculture);
IF you strictly do not want culturespecific then
float.Parse("123.5", CultureInfo.InvariantCulture);
Related
I have a value that is formatted in currency format and displayed in a textbox. I need to pick it and convert it into decimal. e.g. I have $1,633.75 as string and want to cast it as a decimal to save it in the db.
There are questions and some answers available on them already, but they all suggest more complex UDF etc to solve the problem.
Question is, why cannot we use the replace method on a string to remove commas (",") and "$" and simply use decimal.Parse?
Say tbAmountPaid is $1,633.75
What is downside of just doing:
decimal.Parse(tbAmountPaid.Text.Replace(",","").Replace("$",""))
to get decimal type 1633.75 value?
Downside is that hardcoding. You never know the culture and the format in which string is written. There could be multiple bugs in the string itself. If you do hard coding you may end up having a bug in your code
I recommend you to use the format provider. I took code from here
https://learn.microsoft.com/en-us/dotnet/api/system.decimal.parse?redirectedfrom=MSDN&view=netframework-4.7.2#System_Decimal_Parse_System_String_System_Globalization_NumberStyles_System_IFormatProvider_
string value;
decimal number;
NumberStyles style;
CultureInfo provider;
value = "$1,633.75";
style = NumberStyles.Number | NumberStyles.AllowCurrencySymbol;
provider = new CultureInfo("en-US");
number = Decimal.Parse(value, style, provider);
Console.WriteLine("'{0}' converted to {1}.", value, number);
OK, so you're not asking how to do it, you're asking "why not do it this way?"...
Your alternative takes more effort to type than the correct solution,
More effort for the computer to process,
More memory usage (since strings are immutable),
Compiles to larger IL,
Your approach is culture specific. Some cultures use dot for the thousand separator and comma for the decimal place, let alone a different currency symbol.
Turning the question around, what do you feel is better about your approach?
I need to format the Decimal variables Latitude=9113267; Longitude=59300357;
to string format 9,113267 and 59,300357
Thx
john
VascoP is right in how to convert the number to a "proper" decimal but he is wrong about how to convert those decimal values to a string. the ToString method has an overload whose signature is
public string ToString(IFormatProvider provider)
See: http://msdn.microsoft.com/en-us/library/3ebe5aks.aspx
You can use this to create a culture specific string. The examples on the linked page show how to do it but for completeness of answer an example might be:
(Latitude/1000000).ToString(CultureInfo.CreateSpecificCulture("en-GB") // Outputs with a "." decimal separator
(Latitude/1000000).ToString(CultureInfo.CreateSpecificCulture("de-DE") // Outputs with a "," decimal separator
I assume you have a specific culture that you want to be able to understand this so you should use the correct culture. That makes it much easier to change later if you want (eg you can pick up the culture from a global config setting) or have a user preference for the number format, etc.
Also if you start using custom formats (eg to put thousand separators in) then the cultureinfo object will again do the right thing.
It should also be noted at the end of all this that you may just need the .ToString if the default culture is actually the one you are using. You didn't provide that info though so I just assumed that a simple ToString wouldn't be doing the trick.
(Latitude/1000000).ToString().Replace('.', ',');
(Longitude/1000000).ToString().Replace('.', ',');
EDIT: Although this works, as stated by Chris, it is not best practice. You should use his solution instead.
When I try to convert a string to float:
Console.WriteLine(float.Parse("6.59"));
it throws an exception:
Unhandled Exception: System.FormatException: Input string was not in a correct f
ormat.
at System.Number.ParseSingle(String value, NumberStyles options, NumberFormat
Info numfmt)
When I try it like this:
Console.WriteLine(Convert.ToSingle("6.59"));
It throws the same exception:
Unhandled Exception: System.FormatException: Input string was not in a correct f
ormat.
at System.Number.ParseSingle(String value, NumberStyles options, NumberFormat
Info numfmt)
at System.Convert.ToSingle(String value)
Can you explain why this happens?
The single argument Parse method uses the current culture to parse the string. If your current culture uses some other decimal separator, this will fail.
Try using the invariant culture:
float.Parse("6.59", CultureInfo.InvariantCulture)
The problem here is your culture.
Either set the invariant culture like this:
float.Parse("6.59", CultureInfo.InvariantCulture)
or use the correct decimal separator for your culture
float.Parse("6,59")
I wonder why you are using a literal string. If you are having problems entering literal floats, you can use
Console.WriteLine(6.59f)
If you do it this way culture doesn't matter because the value is decided at compile time.
You are probably using a culture that uses the , as a decimal seperator.
You could try to Parse using the InvariantCulture:
float.Parse("6.59", CultureInfo.InvariantCulture)
Culture - specific things. What's your default culture?
Some cultures use "," instead of ".". You can try this:
float.Parse("6.59", CultureInfo.InvariantCulture);
There could be problem with Locale/Culture. You need to set , instead of . for the decimal separator.
I know everyone here has already given the reason for the problem experienced but perhaps somebody should just expand on why Invariant fixes it.
The CultureInfo class is used either directly or indirectly by classes that format, parse, or manipulate culture-specific data, such as String, DateTime, DateTimeOffset, and the numeric types to deal with the differences in the way different cultures write these types.
In case of the decimal type some cultures use a period(.) whilst others use a comma (,). By default when you are using the Conversion Libraries it will make use of your local culture (that is the country your OS to configured for).
By specifying Invariant you say that you expect thousand separators to be commas(,) and decimal deliminator to be a period(.) as it is in most cultures.
A big problem that sometimes happens is that these cultural conventions change from the OS point of view. For example the South African (ZA) culture info used to behave like the invariant culture. Microsoft changed this with Windows 8 where the decimal suddenly became a comma and the thousand separator a space.This resulted in many legacy systems written in .Net suddently breaking when one migrated them to newer operating systems.
In the end, deal normalize all local culture info to invariant and persist and deal with them in your business logic in this format. Then localize it back on the front end. Same goes for DateTime, as soon as possible convert to UTC, and only back when you render an output.
You could also try Convert class to perform this task.
Convert.ToDecimal("6.59");
I have a textbox accepting user input; I am trying to use this user input it to populate this member of one of my business objects:
public System.Decimal? ExchangeRate
The application is localized - I need to support at the same time cultures that accept these as valid inputs: "1,5" and "1.5"
The code I have now is:
var culture = Thread.CurrentThread.CurrentUICulture;
int exchangeRate;
int.TryParse(txtExchangeRate.Text, NumberStyles.Number, culture,
out exchangeRate);
entity.ExchangeRate = exchangeRate;
When the user culture is set to a culture that expects the "1,5" format (comma as decimal separator) - e.g "ro-RO", I want the value that gets stored in entity.ExchangeRate to be 1.5; however, when running the code above, it gets converted to 15 instead.
Any suggestions on how to convert these various formats so that the data that gets stored in my business entity is "1.5" (point as decimal separator)?
Thanks.
You guys were right - it made sense to use Thread.CurrentThread.CurrentCulture instead of Thread.CurrentThread.CurrentUICulture and decimal.TryParse instead of int.TryParse.
But these changes would still not solve my problem. And after playing around with the code some more, I can now simplify the issue to this:
I am using a telerik RadNumericTextBox control which enforce users to use the correct format based on their culture. So, when Thread.CurrentThread.CurrentCulture is set to "ro-RO", it will only accept the "1,5" format, and when it's set to "en-GB", it will only accept the "1.5" format.
Here's the code I am using now:
decimal exchangeRate;
decimal.TryParse(txtExchangeRate.Text, out exchangeRate);
entity.ExchangeRate = exchangeRate;
Case 1: current culture is "en-GB" - accepted input is "1.5" , exchangeRate is set to 1.5 - everything works fine.
Case 2: current culture is "ro-RO" - accepted input is "1,5" , but after executing the decimal.TryParse... line, exchangeRate is set to 15 - wrong, obviously.
I should also mention that in this case, the value of txtExchangeRate.Text is also shown as "1.5" in my Watch window.
So, it looks like decimal.TryParse will take into consideration the current culture, but I can't find a way to actually make it work properly for me. Any suggestions?
OK, here's the code that seems to work on both cases I described in my above post (1. culture "ro-RO", comma as decimal separator and 2. culture "en-GB", dot as decimal separator):
decimal exchangeRate;
decimal.TryParse(txtExchangeRate.Text, NumberStyles.Any,
CultureInfo.InvariantCulture, out exchangeRate);
entity.ExchangeRate = exchangeRate;
Obviously, int cannot hold 1.5 ! :-) Use float instead.
Use CurrentCulture instead of CurrentUICulture. My culture is fr-BE (therefore accepts 1,5 but my Windows UI is English, which doesn't).
I would make the float.Parse() test with both CurrentCulture AND InvariantCulture: By the time some programs learned to accept "1,5", everybody was used to type "1.5". There's nothing which bothers me more than Excel requiring me to type 1,5 when I say 1.5 ! Also, here in Belgium, the 1st year government launched the web-based tax declaration, the site forced you to use commas instead of periods as decimal points. Everybody was wondering why the figures entered were refused!
So be nice to your users and accept both.
FYI I know this isn't your problem, but its a pointer for other people who might be doing this:
When you set your culture, you can't have your application be able to handle input of different cultures. It must be of the type that you have specified.
Therefore, if you set ro-RO as the culture, it won't understand both 1.5 and 1,5 as the same thing.
You should probably be using CurrentCulture (as opposed to CurrentUICulture) for localization (e.g. date/number formatting).
How do you think is really necessary to provide IFormatProvider in method String.Format(string, object) ?
Is it better to write full variant
String.Format(CultureInfo.CurrentCulture, "String is {0}", str);
or just
String.Format("String is {0}", str);
?
In general, you will want to use InvariantCulture if the string you are generating is to be persisted in a way that is independent of the current user's culture (e.g. in the registry, or in a file).
You will want to use CurrentCulture for strings that are to be presented in the UI to the current user (forms, reports).
Subtle bugs can arise if you use CurrentCulture where you should be using InvariantCulture: bugs that only come to light when you have multiple users with different cultures accessing the same registry entry or file, or if a user changes his default culture.
Explicitly specifying CurrentCulture (the default if the IFormatProvider argument is omitted), is essentially documentation that demonstrates that you have considered the above and that the string being generated should use the current user's culture. That's why FxCop recommends that you should specify the IFormatProvider argument.
If you do not specify the IFormatProvider (or equivalently pass null) most argument types will eventually fall through to being formatted according to CultureInfo.CurrentCulture. Where it gets interesting is that you can specify a custom IFormatProvider that can get first crack at formatting the arguments, or override the formatting culture depending on other context.
Note that CultureInfo.CurrentCulture affects argument formatting, not resource selection; resource selection is controlled by CultureInfo.CurrentUICulture.
No, you do not need to specify the culture unless your string contains culture specific elements such as decimal separators, currency, etc., which have to be rendered depending on the culture.
It is especially useful if you care about localization (Globalization) in your application. That is, if you want your app to support multiple languages and culture specific formats, then you should use that.