Decimal ToString() conversion issue in C#

Question

I am facing a problem when I try to convert decimal? to 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, what could be reason for this.

Answer 1

Decimal preserves any trailing zeroes in a Decimal number. If you want two 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 is a floating-point value that consists of a sign, a numeric value where each digit in the value ranges from 0 to 9, and a scaling factor that indicates the position of a floating decimal point that separates the integral and fractional parts of the numeric value.

The binary representation of a Decimal value consists of a 1-bit sign, a 96-bit integer number, and a scaling factor used to divide the 96-bit integer and specify what portion of it is a decimal fraction. The scaling factor is implicitly the number 10, raised to an exponent ranging from 0 to 28. Therefore, the binary representation of a Decimal value is of the form, ((-2⁹⁶ to 2⁹⁶) / 10^{(0 to 28)}), where -2⁹⁶-1 is equal to MinValue, and 2⁹⁶-1 is equal to MaxValue.

The scaling factor also preserves any trailing zeroes in a Decimal number. Trailing zeroes do not affect the value of a Decimal number in arithmetic or comparison operations. However, >>trailing zeroes can be revealed by the ToString method if an appropriate format string is applied<<.

Remarks:

1. the decimal multiplication needs to be casted to decimal, because Nullable<decimal>.ToString has no format provider

2. as Chris pointed out you need to handle the case that the Nullable<decimal> is null. One way is using the Null-Coalescing-Operator:

   ((decimal)(decimalValue ?? 0 * 100)).ToString("N2")
   

This article from Jon Skeet is worth reading:

Decimal floating point in .NET (seach for keeping zeroes if you're impatient)

Answer 2

Since you using Nullable<T> as your decimal, Nullable<T>.ToString() method doesn't have overloading takes parameters that you can use for formatting.

Instead of, you can explicitly cast it to decimal and you can use .ToString() method for formatting.

Just use "0.00" format in your .ToString() method.

decimal? decimalValue = .1211M;
string value = ((decimal)(decimalValue * 100)).ToString("0.00");
Console.WriteLine(value);

Output will be;

12.11

Here is a DEMO.

As an alternative, you can use Nullable<T>.Value without any conversation like;

string value = (decimalValue * 100).Value.ToString("0.00");

Check out for more information from Custom Numeric Format Strings

Answer 3

Alternatively, you can specify the format "F2", like so: string val = decVal.ToString("F2") as this specifies 2 decimal places.

Answer 4

Use the fixed-point ("F) format specifier .

   string value = (decimalValue * 100).ToString("F");

The default precision specifier is based on value of NumberFormatInfo.NumberDecimalDigits property which by default has value 2. So if don't specify a digit aftyer "F" , it by default specifies two decimal digits.

F0 - No decimal places
F1 - One decimal place

Answer 5

In case you do not want to limit to a certain amount of decimal digits:

decimal? decimalValue = .1211;
string value = decimalValue == null 
               ? "0"
               : decimalValue == 0
               ? "0"
               : (decimalValue * 100).ToString().TrimEnd('0');

This will trim any (if any) trailing zeroes of the string and also return "0" if decimalValue is null. If the value is 0 then "0" is returned without trimming.

Answer 6

String.Format("{0:0.00}", decimalValue * 100);

You can use .Format() as an alternative to .ToString("0.00").

Answer 7

Since decimal? does not have a ToString(string format) overload, the easiest way is to use String.Format instead which will provide consistent results with the null case for decimalValue as well (resulting in an empty string) when compared to your original code:

string value = String.Format("{0:#.##}", decimalValue * 100);

But there are some other considerations for other numbers that you weren't clear on.

If you have a number that does not produce a value greater than 0, does it show a leading zero? That is, for 0.001211, does it display as 0.12 or .12? If you want the leading zero, use this instead (notice the change from #.## to 0.##):

string value = String.Format("{0:0.##}", decimalValue * 100);

If you have more than 2 significant decimal places, do you want those displayed? So if you had .12113405 would it display as 12.113405? If so use:

string value = String.Format("{0:#.############}", decimalValue * 100);

(honestly, I think there must be a better formatting string than that, especially as it only supports 12 decimal places)

And of course if you want both leading zeros and multiple decimal places, just combine the two above:

string value = String.Format("{0:0.############}", decimalValue * 100);