variable decimal places in .Net string formatters?

Question

Fixed decimal places is easy

String.Format("{0:F1}", 654.321); 

gives

654.3 

How do I feed the number of decimal places in as a parameter like you can in C? So

String.Format("{0:F?}", 654.321, 2); 

gives

654.32 

I can't find what should replace the ?

Answer 1

The string to format doesn't have to be a constant.

int numberOfDecimalPlaces = 2; string formatString = String.Concat("{0:F", numberOfDecimalPlaces, "}"); String.Format(formatString, 654.321); 

Answer 2

Use NumberFormatInfo:

Console.WriteLine(string.Format(new NumberFormatInfo() { NumberDecimalDigits = 2 }, "{0:F}", new decimal(1234.567))); Console.WriteLine(string.Format(new NumberFormatInfo() { NumberDecimalDigits = 7 }, "{0:F}", new decimal(1234.5)));