限制双精度字符的最大字符数

Question

Is there an elegant way to convert a double to a string so it's rounded to fit within a maximum total length but is otherwise similar to the default neutral culture format?

I don't want to just limit the number of decimal places because the number of characters used for sign and exponent might change, or it might not be in scientific notation.

Eg, with a maximum of 20 characters

-1.23456789012345E-67

should appear as

-1.2345678901235E-67

while

123 should appear as 123 , not 1.23E+02 .

Answer 1

As Sintar mentioned G format specifier should do all you need.

double s = 1.31956544564371E+28;
Console.WriteLine("{0:G5}",s);  // will print 1.3196E+28

The following is a extension method might be helpful:

public static class doubleExtensions
{
    public static string GetDoubleString(this double source,int numOfChars){
        string  temp = "{0:G" + numOfChars + "}";
        return string.Format(temp,source);
    }
}