MSDN Magazine - November 2008 - (Page 17)

MelIttA ANderseN CLR InsIde Out International Applications Most programs present some sort of data to users. Clearly applications with a GUI, such as a Windows Presentation Foundation (WPF) or Windows Forms application, have been designed to provide information to users. However, even simple console applications display text. The process of globalization is making sure that your application can handle data that comes from different cultures. This can be as simple as making sure your calendar title is wide enough to handle Hawaiian month names or using the negative number format that your users expect. Globalization is different from localization, which is actually translating resources from your application into different languages. Your application needs to be aware of globalization even if it is only in one language. Here’s an example of how there can be variations, even in an application that has not been translated. Certain types of data, such as dates, can be formatted in a variety of ways. Figure 1 lists just a few formats that use English names for months and days of the week. All the entries represent the same piece of data. But users have certain expectations about date formats, and they can indicate their preference via settings in the control panel. So if your program makes a call to DateTime.Now.ToString, any number of strings could be returned. If you have not specified a format, ToString automatically picks up the user’s preferences. The date string “1/2/03” is meaningless unless you know what each part of the string represents. You would think that knowing the format string would help you interpret the meaning of the data. But even that is no guarantee. Not everyone uses the same calendar. In fact, the System.Globalization namespace currently supports 15 different calendars. So the string “6/26/1980” interpreted as “M/d/ yy” might represent different days in the Gregorian calendar and the Julian calendar. (There are a number of Web sites that can convert dates to different calendars.) Interestingly enough, the same interpretation issues apply to numbers. Some users might expect the decimal separator to be a period, while others are used to seeing a comma. So when one user expects 1.23, another might expect 1,23. It gets even more complicated when you’re dealing with negative numbers. If you look at System.Globalization.NumberFormatInfo.NumberNegativePattern, you will see that the Microsoft .NET Framework stores 5 patterns for the placement of the negative sign. And that’s with only one symbol. It stores 16 different patterns for negative currency values in NumberFormatInfo.CurrencyNegativePattern. Figure 1 Some Date Formats Date String 6/26/1980 26/6/1980 Thursday, June 26, 1980 June 26 1980-06-26 Thu, 26 June 1980 Format String M/d/yyyy d/M/yyyy dddd, MMMM dd, yyyy MMMM dd yyyy-MM-dd ddd, dd MMMM yyyy As you might guess, when storing data as strings you should always explicitly indicate the format you wish to follow and use that same format for both the ToString and Parse methods. Remember, some strings can be ambiguous without context. Of course, all this fancy formatting matters only for display purposes; it is a best practice to pick an invariant representation for stored data that will only be read by a machine. The Framework provides a mechanism for this with CultureInfo.InvariantCulture. With so many options for formatting, how are you to know which one to choose? Fortunately, the .NET Framework has an infrastructure in place for formatting data for display. As you’ve seen, user preferences can be followed automatically. But how does the Framework decide what to use when a user hasn’t specified? Taking a closer look at the System.Globalization namespace can help answer this question. The contents of System.Globalization are used to describe information about a culture. We already know that it contains 15 calendars and 16 ways to format negative currency values. In addition, it has other culture-specific properties for time and numbers, as well as classes for storing information about languages and regions. It also contains a mechanism to organize and group this information for use. That mechanism is the CultureInfo class, which stores information about a culture, including number formatting, date formatting, and calendar, as well as names for the culture and information about the writing system. CultureInfo objects are created using an identifier for a particular culture. For example, in order to create an object that contains This column is based on a prerelease version of Silverlight. All information is subject to change. Send your questions and comments to clrinout@microsoft.com. November 2008 17

Table of Contents Feed for the Digital Edition of MSDN Magazine - November 2008

Contents MSDN Magazine - November 2008 Toolbox CLR Inside Out Data Points Cutting Edge Security Briefs Test Your Security IQ Agile SDL Access Control Utility Spotlight RIA Test Run Wicked Code Foundations Team System End Bracket

MSDN Magazine - November 2008

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