C# String.Format with Nested Number Formatting

Question

I'm trying to create a generic specification string generator that can format to any number of decimal places, i.e. "Temperature must be 20.5 C to 40.0 C", "Humidity must be 15 % to 85 %", "Gas inlet pressure must be 2.25 ATM to 2.75 ATM", etc.

Right now, I'm doing the following which works but I feel that it can be simplified.

public static string SpecToString(double minimum, double maximum, int digits)
{
    string numberFormatMin = "{0:f" + digits + "}";
    string numberFormatMax = "{1:f" + digits + "}";

    return String.Format(numberFormatMin + " to " + numberFormatMax, minimum, maximum);
}

Is there anyway for String.Format to "nest" parameters like the following? As is, it throws an exception with input string not in the correct format.

public static string SpecToString2(double minimum, double maximum, int digits)
{
    return String.Format("{0:f{2}} to {1:f{2}}", minimum, maximum, digits);
}

The values are stored in a database at a reference unit of measure. Then they can be converted, i.e. pressure in bar, PSI, ATM, Torr all of which would display with different decimal places. — Adam Milecki, Commented Sep 18, 2015 at 20:03

Sten Petrov · Accepted Answer · 2015-09-18 19:45:59Z

1

You can use two String.Format calls if you find that "simpler"

var temp = string.Format("{{0:f{0}}} to {{1:f{0}}}", digits);
return string.Format(temp, minimum, maximum);

answered Sep 18, 2015 at 19:45

Sten Petrov

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