string - Decimal ToString() conversion issue in C# -

i facing problem when try convert decimal? string. scenario is

decimal decimalvalue = .1211; string value = (decimalvalue * 100).tostring(); 

current result : value = 12.1100

expected result : value = 12.11

please let me know, reason this.

decimal preserves trailing zeroes in decimal number. if want 2 decimal places instead:

decimal? decimalvalue = .1211m; string value = ((decimal)(decimalvalue * 100)).tostring("#.##") 

http://msdn.microsoft.com/en-us/library/0c899ak8.aspx

or

string value = ((decimal)(decimalvalue * 100)).tostring("n2") 

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

from system.decimal:

a decimal number floating-point value consists of sign, numeric value each digit in value ranges 0 9, , a scaling factor indicates position of floating decimal point separates integral , fractional parts of numeric value.

the binary representation of decimal value consists of 1-bit sign, 96-bit integer number, , scaling factor used divide 96-bit integer , specify portion of decimal fraction. scaling factor implicitly number 10, raised exponent ranging 0 28. therefore, binary representation of decimal value of form, ((-2⁹⁶ 2⁹⁶) / 10^{(0 28)}), -2⁹⁶-1 equal minvalue, , 2⁹⁶-1 equal maxvalue.

the scaling factor preserves trailing zeroes in decimal number. trailing zeroes not affect value of decimal number in arithmetic or comparison operations. however, >>trailing zeroes can revealed tostring method if appropriate format string applied<<.

remarks:

1. the decimal multiplication needs casted decimal, because nullable<decimal>.tostring has no format provider

2. as chris pointed out need handle case nullable<decimal> null. 1 way using null-coalescing-operator:

   ((decimal)(decimalvalue ?? 0 * 100)).tostring("n2") 

this article jon skeet worth reading:

decimal floating point in .net (seach keeping zeros if you're impatient)