ExcelNumberFormat

.NET library to parse ECMA-376 number format strings and format values like Excel and other spreadsheet softwares.

Install via NuGet

If you want to include ExcelNumberFormat in your project, you can install it directly from NuGet

To install ExcelNumberFormat, run the following command in the Package Manager Console

PM> Install-Package ExcelNumberFormat

Usage

var format = new NumberFormat("#.##");
Console.WriteLine(format.Format(1234.56, CultureInfo.InvariantCulture));

Features

Parses and formats most custom number formats as expected: decimal, percent, thousands, exponential, fraction, currency, date/time, duration, text.
Supports multiple sections with conditions.
Formats values with relevant constants from CultureInfo.
Supports DateTime, TimeSpan and numeric values for date and duration formats.
Supports both 1900- and 1904-based numeric datetimes (Excel on Mac uses 1904-based dates).
Targets net20 and netstandard1.0 for max compatibility.

Formatting .NET types

The Format() method takes a value of type object as parameter. Internally, the value is cast or converted to a specific .NET type depending on the kind of number format:

Format Kind	Example	.NET type	Conversion strategy
Number	0.00	double	Convert.ToDouble()
Fraction	0/0	double	Convert.ToDouble()
Exponent	#0.0E+0	double	Convert.ToDouble()
Date/Time	hh:mm	DateTime	ExcelDateTime.TryConvert()
Duration	[hh]:mm	TimeSpan	Cast or TimeSpan.FromDays()
General	General	(any)	CompatibleConvert.ToString()
Text	;;;"Text: "@	string	Convert.ToString()

In case of errors, Format() returns the value from CompatibleConvert.ToString().

CompatibleConvert.ToString() formats floats and doubles with explicit precision, or falls back to Convert.ToString() for any other types. ExcelDateTime.TryConvert() uses DateTimes as is, or converts numeric values to a DateTime with adjustments for legacy Excel behaviors.

TODO/notes