System.Globalization.CultureInfo.InvariantCulture property
This article provides supplementary remarks to the reference documentation for this API.
The invariant culture is culture-insensitive; it's associated with the English language but not with any country/region. You specify the invariant culture by name by using an empty string ("") in the call to a CultureInfo instantiation method. This property, CultureInfo.InvariantCulture, also retrieves an instance of the invariant culture. It can be used in almost any method in the System.Globalization namespace that requires a culture. The objects returned by properties such as CompareInfo, DateTimeFormat, and NumberFormat also reflect the string comparison and formatting conventions of the invariant culture.
Unlike culture-sensitive data, which is subject to change by user customization or by updates to the .NET Framework or the operating system, invariant culture data is stable over time and across installed cultures and cannot be customized by users. This makes the invariant culture particularly useful for operations that require culture-independent results, such as formatting and parsing operations that persist formatted data, or sorting and ordering operations that require that data be displayed in a fixed order regardless of culture.
String operations
You can use the invariant culture for culture-sensitive string operations that are not affected by the conventions of the current culture and that are consistent across cultures. For example, you may want sorted data to appear in a fixed order or apply a standard set of casing conventions to strings regardless of the current culture. To do this, you pass the InvariantCulture object to a method that has a CultureInfo parameter, such as Compare(String, String, Boolean, CultureInfo) and ToUpper(CultureInfo).
Persisting data
The InvariantCulture property can be used to persist data in a culture-independent format. This provides a known format that does not change and that can be used to serialize and deserialize data across cultures. After the data is deserialized, it can be formatted appropriately based on the cultural conventions of the current user.
For example, if you choose to persist date and time data in string form, you can pass the InvariantCulture object to the DateTime.ToString(String, IFormatProvider) or DateTimeOffset.ToString(IFormatProvider) method to create the string, and you can pass the InvariantCulture object to the DateTime.Parse(String, IFormatProvider) or DateTimeOffset.Parse(String, IFormatProvider, DateTimeStyles) method to convert the string back to a date and time value. This technique ensures that the underlying date and time values do not change when the data is read or written by users from different cultures.
The following example uses the invariant culture to persist a DateTime value as a string. It then parses the string and displays its value by using the formatting conventions of the French (France) and German (Germany) cultures.
using System;
using System.IO;
using System.Globalization;
public class Example
{
public static void Main()
{
// Persist the date and time data.
StreamWriter sw = new StreamWriter(@".\DateData.dat");
// Create a DateTime value.
DateTime dtIn = DateTime.Now;
// Retrieve a CultureInfo object.
CultureInfo invC = CultureInfo.InvariantCulture;
// Convert the date to a string and write it to a file.
sw.WriteLine(dtIn.ToString("r", invC));
sw.Close();
// Restore the date and time data.
StreamReader sr = new StreamReader(@".\DateData.dat");
String input;
while ((input = sr.ReadLine()) != null)
{
Console.WriteLine("Stored data: {0}\n" , input);
// Parse the stored string.
DateTime dtOut = DateTime.Parse(input, invC, DateTimeStyles.RoundtripKind);
// Create a French (France) CultureInfo object.
CultureInfo frFr = new CultureInfo("fr-FR");
// Displays the date formatted for the "fr-FR" culture.
Console.WriteLine("Date formatted for the {0} culture: {1}" ,
frFr.Name, dtOut.ToString("f", frFr));
// Creates a German (Germany) CultureInfo object.
CultureInfo deDe= new CultureInfo("de-De");
// Displays the date formatted for the "de-DE" culture.
Console.WriteLine("Date formatted for {0} culture: {1}" ,
deDe.Name, dtOut.ToString("f", deDe));
}
sr.Close();
}
}
// The example displays the following output:
// Stored data: Tue, 15 May 2012 16:34:16 GMT
//
// Date formatted for the fr-FR culture: mardi 15 mai 2012 16:34
// Date formatted for de-DE culture: Dienstag, 15. Mai 2012 16:34
Imports System.Globalization
Imports System.IO
Module Example
Public Sub Main()
' Persist the date and time data.
Dim sw As New StreamWriter(".\DateData.dat")
' Create a DateTime value.
Dim dtIn As DateTime = DateTime.Now
' Retrieve a CultureInfo object.
Dim invC As CultureInfo = CultureInfo.InvariantCulture
' Convert the date to a string and write it to a file.
sw.WriteLine(dtIn.ToString("r", invC))
sw.Close()
' Restore the date and time data.
Dim sr As New StreamReader(".\DateData.dat")
Dim input As String = String.Empty
Do While sr.Peek() >= 0
input = sr.ReadLine()
Console.WriteLine("Stored data: {0}" , input)
Console.WriteLine()
' Parse the stored string.
Dim dtOut As DateTime = DateTime.Parse(input, invC, DateTimeStyles.RoundtripKind)
' Create a French (France) CultureInfo object.
Dim frFr As New CultureInfo("fr-FR")
' Displays the date formatted for the "fr-FR" culture.
Console.WriteLine("Date formatted for the {0} culture: {1}" ,
frFr.Name, dtOut.ToString("f", frFr))
' Creates a German (Germany) CultureInfo object.
Dim deDe As New CultureInfo("de-De")
' Displays the date formatted for the "de-DE" culture.
Console.WriteLine("Date formatted for {0} culture: {1}" ,
deDe.Name, dtOut.ToString("f", deDe))
Loop
sr.Close()
End Sub
End Module
' The example displays the following output:
' Stored data: Tue, 15 May 2012 16:34:16 GMT
'
' Date formatted for the fr-FR culture: mardi 15 mai 2012 16:34
' Date formatted for de-DE culture: Dienstag, 15. Mai 2012 16:34
Security decisions
If you are making a security decision (such as whether to allow access to a system resource) based on the result of a string comparison or a case change, you should not use the invariant culture. Instead, you should perform a case-sensitive or case-insensitive ordinal comparison by calling a method that includes a StringComparison parameter and supplying either StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase as an argument. Code that performs culture-sensitive string operations can cause security vulnerabilities if the current culture is changed or if the culture on the computer that is running the code differs from the culture that is used to test the code. In contrast, an ordinal comparison depends solely on the binary value of the compared characters.
