Include If Else statement in String.Format

Question

I have the following statemnt.

  timespan = timespan.FromSeconds(236541)
  formattedTimeSpan = String.Format("{0} hr {1} mm {2} sec", Math.Truncate(timespan.TotalHours), timespan.Minutes, timespan.Seconds)

I have to have it formatted as "hrs mn sec" if there are more than one hour. I want to check this within the String.Format above.

Thanks.

Answer 1

Probably the cleanest way to do this is to write your own ICustomFormatter. Here's an example of a convenient pluralizer format:

using System;

public class PluralFormatter : IFormatProvider, ICustomFormatter {

   public object GetFormat(Type formatType) {
      if (formatType == typeof(ICustomFormatter))
         return this;
      else
         return null;
   }

   public string Format(string format, object arg, 
                          IFormatProvider formatProvider)
   {   
      if (! formatProvider.Equals(this)) return null;

      if (! format.StartsWith("^")) return null;

      String[] parts = format.Split(new char[] {'^'});
      int choice = ((int) arg) == 1 ? 1 : 2;
      return String.Format("{0} {1}", arg, parts[choice]);
   }

   public static void Main() {
      Console.WriteLine(String.Format(
         new PluralFormatter(),
         "{0:^puppy^puppies}, {1:^child^children}, and {2:^kitten^kittens}", 
         13, 1, 42
      ));
   }
}

The output is, as one might've guessed (and as seen on ideone.com):

13 puppies, 1 child, and 42 kittens

MSDN links

• Custom Formatting with ICustomFormatter
• System.ICustomFormatter
• System.IFormatProvider

Answer 2

One possibility is to make the plural part of the format string, and write:

formattedTimeSpan = String.Format("{0} hr{1} {2} mm {3} sec",
    Math.Truncate(timespan.TotalHours),
    Math.Truncate(timespan.TotalHours) == 1 ? "" : "s",
    timespan.Minutes,
    timespan.Seconds);

This will insert a "s" into the output if the output says anything other than "1 hr".

Note that this is not friendly to localization: other languages form plurals differently than English.

Answer 3

No magic here. Why would you code in whatever condition format may offer, when you can code in C#?

To avoid duplicated code, you might as promote some expressions to variables, and use the condition on them:

timespan = timespan.FromSeconds(236541);
int hours = Math.Truncate(timespan.TotalHours);
string hoursUnit = hours == 1 ? "hr" : "hrs";
formattedTimeSpan = String.Format("{0}{1} {2} mm {3} sec",
                        hours, hoursUnit, timespan.Minutes, timespan.Seconds);