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Using the InvariantCulture Property

The CultureInfo.InvariantCulture property is neither a neutral nor a specific culture. It is a third type of culture that is culture-insensitive. It is associated with the English language but not with a country or region. You can use InvariantCulture in almost any method in the System.Globalization namespace that requires a culture. However, you should use the invariant culture only for processes that require culture-independent results, such as system services. In other cases, it produces results that might be linguistically incorrect or culturally inappropriate.

You should also use InvariantCulture when a security decision will be made based on the result of a string comparison or case change. The default implementations of methods such as String.Compare, String.ToUpper, and String.ToLower use the CultureInfo.CurrentCulture property. Code that performs culture-sensitive string operations can cause security vulnerabilities if CultureInfo.CurrentCulture is changed or if the culture on the computer on which the code runs differs from the culture the developer used to test the code. The behavior expected by the developer writing a string operation will differ from the code's actual behavior on the computer on which the operation runs. To eliminate cultural variations and ensure consistent results regardless of the value of CultureInfo.CurrentCulture, use overloads of the String.Compare, String.ToUpper and String.ToLower methods that accept a CultureInfo parameter, specifying the CultureInfo.InvariantCulture property for the CultureInfo parameter. For more information about using the InvariantCulture property to perform culture-insensitive string operations, see Culture-Insensitive String Operations.

The following example demonstrates how to initialize CultureInfo with the invariant culture by using an empty string ("") or CultureInfo.InvariantCulture.

' The following lines are equivalent.
CultureInfo Invc = New CultureInfo("")
CultureInfo Invc = CultureInfo.InvariantCulture
[C#]
// The following lines are equivalent.
CultureInfo Invc = New CultureInfo("");
CultureInfo Invc = CultureInfo.InvariantCulture;

The InvariantCulture is useful for storing data that will not be displayed directly to end users. Storing data in a culture-independent format guarantees a known format that does not change. When users from different cultures access the data, it can be formatted appropriately based on the user. For example, if you store DateTime types in a text file, formatted for the InvariantCulture, use the InvariantCulture property when you call the DateTime.ToString method to store the strings and the Date.Parse method to retrieve the strings. This will ensure that the underlying values of the DateTime types do not change when the data is read or written by users from different cultures.

The following code example illustrates writing a DateTime to a file as a string formatted for the InvariantCulture using the DateTime.ToString method. The string is then read from the file in the InvariantCulture format and parsed to a DateTime using the Date.Parse method. The DateTime is then formatted and displayed for the cultures "fr-FR" and "ja-JP".

Imports System
Imports System.IO
Imports System.Globalization
Imports Microsoft.VisualBasic

Public Class TextToFile
   Private const FILE_NAME As String = "MyDateFile.txt"   
   
   Public Shared Sub Main()
      If File.Exists(FILE_NAME) Then
         Console.WriteLine("{0} already exists!", FILE_NAME)
         Return
      End If

      Dim sw As StreamWriter = File.CreateText(FILE_NAME)
      
      'Creates a DateTime.
      Dim dtIn As DateTime = DateTime.Now
      Dim InvC As CultureInfo = CultureInfo.InvariantCulture
      ' Writes the string to the file formatted for InvariantCulture.
      sw.WriteLine(dtIn.ToString("d", InvC))
      sw.Close()
      
      If Not File.Exists(FILE_NAME) Then
         Console.WriteLine("{0} does not exist!", FILE_NAME)
         Return
      End If
      
      Dim sr As StreamReader = File.OpenText(FILE_NAME)
      Dim filedate As String
      filedate = sr.Readline()
      While Not filedate Is Nothing
         Console.WriteLine(ControlChars.Newline + "The date stored in _
            the file formatted for the invariant culture is:" + _
            ControlChars.Newline + " {0}", filedate )
         
         ' Creates a new DateTime and parses the 
         ' string stored in the file.
         Dim dtout as DateTime = DateTime.Parse(filedate, InvC)
         
         ' Creates a CultureInfo set to "fr-FR".
         Dim frc As New CultureInfo("fr-FR")
         ' Displays the date formatted for the "fr-FR" culture.
         Console.WriteLine(ControlChars.Newline + "The date read from _
            the file and formatted for the culture ""fr-FR"" is:" + _
            ControlChars.Newline + " {0}", dtout.ToString("d", frc))
         
         ' Creates a CultureInfo set to "ja-JP".
         Dim jpn As New CultureInfo("ja-JP")
         ' Displays the date formatted for the "ja-JP" culture.
         Console.WriteLine(ControlChars.Newline + "The date read from _
            the file and formatted for the culture ""ja-JP"" is:" + _
            ControlChars.Newline + " {0}", dtout.ToString("d", jpn))
        
        filedate = sr.Readline()
      End While
      
      Console.WriteLine(ControlChars.Newline + "The end of the stream _
         has been reached.")
      sr.Close()
   End Sub
End Class
[C#]
using System;
using System.IO;
using System.Globalization;

public class TextToFile 
{
   private const string FILE_NAME = "MyDateFile.txt";
   public static void Main(String[] args) 
   {
      if (File.Exists(FILE_NAME)) 
      {
         Console.WriteLine("{0} already exists!", FILE_NAME);
         return;
      }
      StreamWriter sw = File.CreateText(FILE_NAME);
      
      // Creates a DateTime.      
      DateTime dtIn = DateTime.Now;
      // Creates a CultureInfo set to InvariantCulture.
      CultureInfo InvC = new CultureInfo("");
      // Converts dt to a string formatted for InvariantCulture,
      // and writes it to a file.
      sw.WriteLine (dtIn.ToString("d",InvC));
      sw.Close();

      if (!File.Exists(FILE_NAME)) 
      {
         Console.WriteLine("{0} does not exist!", FILE_NAME);
         return;
      }
      StreamReader sr = File.OpenText(FILE_NAME);
      String date;
      while ((date=sr.ReadLine())!=null) 
      {
         Console.WriteLine("\nThe date stored in the file formatted for 
               the invariant culture is:\n{0}" , date);    

         // Parses the string stored in the file,
         // and stores it in a DateTime.
         DateTime dtout = DateTime.Parse(date, InvC);

         // Creates a CultureInfo set to "fr-FR".
         CultureInfo frc = new CultureInfo("fr-FR");
         // Displays the date formatted for the "fr-FR" culture.
         Console.WriteLine("\nThe date read from the file and formatted 
               for the culture \"fr-FR\" is:\n{0}" , dtout.ToString("d", 
               frc));

         // Creates a CultureInfo set to "ja-JP".
         CultureInfo jpn= new CultureInfo("ja-JP");
         // Displays the date formatted for the "ja-JP" culture.
         Console.WriteLine("\nThe date read from the file and formatted 
               for the culture \"ja-JP\" is:\n{0}" , dtout.ToString("d", 
               jpn));
      }
      Console.WriteLine ("\nThe end of the stream has been reached.");
      sr.Close();
   }
}

This code produces the following output:

The date stored in the file formatted for the invariant culture is:
07/24/2001

The date read from the file and formatted for the culture "fr-FR" is:
24/07/2001

The date read from the file and formatted for the culture "ja-JP" is:
2001/07/24

The end of the stream has been reached.

See Also

Developing World-Ready Applications | CultureInfo Class | CultureInfo.CurrentUICulture Property | CultureInfo.CreateSpecificCulture Method

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