String.Format decimal with sign, fixed number of decimal places, no decimal separator

Question

What is the cleanest, most readable way to String.Format a decimal with the following criteria

start with a sign symbol (+ or -)
a fixed number of fraction digits
no decimal separator
right aligned
pre-padded with "0"'s

For example

123,45 would become "+0012345"
-1123,45 would become "-0112345"

Jamiec · Accepted Answer · 2012-06-26T11:16:07.287

You almost certainly want a Custom numeric format string to pass to the String.Format method.

The custom format string can contain 2 sections (first for positive, second for negative formatting) for which you can supply the literal + or -. So to format with 7 characters zero padded this is something like:

String.Format("{0:'+'0000000;'-'0000000}",yourValue);

However, this will truncate a decimal, and so your input gives

123.45 --> +0000123
-1123.45 --> -0001123

One simple solution is just multiply your number by 100 (to fix the number of decimal digits to 2) before passing it to the above

Live example: http://rextester.com/SZR8690 (C# - sorry, but only demo's the idea)

This could then be wrapped up into an extension method:

<Extension()> 
Public Function ToFixedFormat(ByVal value As Decimal, ByVal numFractionalDigits As Integer)
    Return String.Format("{0:'+'0000000;'-'0000000}",value * Math.Pow(10,numFractionalDigits))
End Function

Live example: http://rextester.com/LSAAA60214 (VB.NET)

Don't worry, I'm fluent in C# too ;) Multiplying: simple and brilliant :) — Boris Callens, Jun 26 '12 at 11:07
@BorisCallens - I thought C# would be ok, but we should always strive to provide code examples in the tagged language of choice. The fixed number of digits was the only part `String.Format` cant do (not without a decimal separator anyway) So your 2 choices are replace the decimal place (as per @Tim's answer) or multiply by the nth power of 10 (as per my answer). — Jamiec, Jun 26 '12 at 11:15

score 3 · Answer 2 · answered Jun 26 '12 at 10:49

Maybe there's something better because it looks a bit clumsy, but it works.

I specify the positive and negative format to enforce the plus-sign for positive numbers and a fixed size string. Then i use the InvariantCulture to enforce the point as decimal separator (i could have used other cultures too). The last step is to remove the point.

Dim value = -1123.45
Dim formatted = value.ToString(
        "+00000.00;-00000.00",
        System.Globalization.CultureInfo.InvariantCulture)
formatted = formatted.Replace(".", "")

As you can see i don't know how to specify no decimal separator.

String.Format decimal with sign, fixed number of decimal places, no decimal separator

2 Answers2