The “c” (or currency) format specifier converts a number to a string that represents a currency amount.

string.Format("{0:c}", 112.236677) // $112.23 - defaults to system

Precision

Default is 2. Use c1, c2, c3 and so on to control precision.

string.Format("{0:C1}", 112.236677) //$112.2
string.Format("{0:C3}", 112.236677) //$112.237
string.Format("{0:C4}", 112.236677) //$112.2367
string.Format("{0:C9}", 112.236677) //$112.236677000

Currency Symbol

1. Pass CultureInfo instance to use custom culture symbol.

   string.Format(new CultureInfo("en-US"), "{0:c}", 112.236677); //$112.24
   string.Format(new CultureInfo("de-DE"), "{0:c}", 112.236677); //112,24 €
   string.Format(new CultureInfo("hi-IN"), "{0:c}", 112.236677); //₹ 112.24
   

2. Use any string as currency symbol. Use NumberFormatInfo as to customize currency symbol.

   NumberFormatInfo nfi = new CultureInfo( "en-US", false ).NumberFormat;
   nfi = (NumberFormatInfo) nfi.Clone();
   nfi.CurrencySymbol = "?";
   string.Format(nfi, "{0:C}", 112.236677); //?112.24
   nfi.CurrencySymbol = "?%^&";
   string.Format(nfi, "{0:C}", 112.236677); //?%^&112.24
   

Position of Currency Symbol

Use CurrencyPositivePattern for positive values and CurrencyNegativePattern for negative values.

NumberFormatInfo nfi = new CultureInfo( "en-US", false ).NumberFormat;        
nfi.CurrencyPositivePattern = 0;
string.Format(nfi, "{0:C}", 112.236677); //$112.24 - default
nfi.CurrencyPositivePattern = 1;
string.Format(nfi, "{0:C}", 112.236677); //112.24$
nfi.CurrencyPositivePattern = 2;
string.Format(nfi, "{0:C}", 112.236677); //$ 112.24
nfi.CurrencyPositivePattern = 3; 
string.Format(nfi, "{0:C}", 112.236677); //112.24 $

Negative pattern usage is the same as positive pattern. A lot more use cases please refer to original link.

Custom Decimal Separator

NumberFormatInfo nfi = new CultureInfo( "en-US", false ).NumberFormat;        
nfi.CurrencyPositivePattern = 0;
nfi.CurrencyDecimalSeparator = "..";
string.Format(nfi, "{0:C}", 112.236677); //$112..24