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c#string-formatting

Why does percentage format specifier multiply by 100?

Why does the 'p' string format for percent multiply the value by 100 before formatting it with the percentage sign?

http://msdn.microsoft.com/en-us/library/dwhawy9k.aspx#PFormatString

The Percent ("P") Format Specifier

The percent ("P") format specifier multiplies a number by 100 and converts it to a string that represents a percentage. The precision specifier indicates the desired number of decimal places. If the precision specifier is omitted, the default numeric precision supplied by the current PercentDecimalDigits property is used.

Is there any way to prevent the value from being multiplied by 100 before formatting? Rather than doing:

(value / 100).ToString("p")
Solution

  • As to the why, "percent" literally means "out of one hundred", so 50% is mathematically equivalent to 0.50. As to formatting, why not just add a percent sign?

    value + "%"

    ... or something like this:

    value.ToString("#.00\\%")