Should I always specify which IFormatProvider to use?

Question

I tried running FxCop on a few assemblies of our product, and I get lots and lots of matches of the "Specify IFormatProvider" rule.

As it happens, some of those are legitimate, but it also matches code like this:

Logger.DebugFormat("Appending file {0}", fileName);

Which can be written as

Logger.DebugFormat(CultureInfo.InvariantCulture, "Appending file {0}", fileName);

The second variant is much harder to read.

So, is it actually recommended to always specifiy the IFormatProvider or is it "just" a limitation of the heuristic used in the rule?

Answer 1

It only applies to methods with an IFormatProvider overload.

To deal with this problem, I have two static classes, InvariantText and CulturedText, that work with strings in the invariant culture and current culture, respectively. For example, I have a Format method in each class. This way, I can do culture-neutral and culture-aware formatting without having to specify an IFormatProvider each time.

Example:

InvariantText.Format("0x{0:X8}",value);

CulturedText.Format("Appending file {0}",file);

InvariantText.Format and CulturedText.Format are simply wrappers to the String.Format method, and accordingly likewise return strings.

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You can even use this pattern to wrap other functions that require culture-neutral and culture-specific strings. For example, create two methods, InvariantLog and CulturedLog that wrap calls to Logger.DebugFormat in your question and take the appropriate IFormatProvider in each case.

Answer 2

It depends. You are aware how and where application will be used, so please consider following MSDN recommendations:

1. If the value will be displayed to the user, use the current culture. See System.Globalization.CultureInfo.CurrentCulture.
2. If the value will be stored and accessed by software (persisted to a file or database), use the invariant culture. See System.Globalization.CultureInfo.InvariantCulture.
3. If you do not know the destination of the value, have the data consumer or provider specify the culture.

PS: I believe FxCop follows the third rule and let you specify the right culture yourself.