String.ToLowerInvariant Method
Returns a copy of this String object converted to lowercase using the casing rules of the invariant culture.
Assembly: mscorlib (in mscorlib.dll)
The invariant culture represents a culture that is culture-insensitive. It is associated with the English language but not with a specific country or region. For more information, see Using the InvariantCulture Property.
If your application depends on the case of a string changing in a predictable way that is unaffected by the current culture, use the ToLowerInvariant method. The ToLowerInvariant method is equivalent to ToLower(CultureInfo.InvariantCulture). The method is recommended when a collection of strings must appear in a predictable order in a user interface control.
Note
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This method does not modify the value of the current instance. Instead, it returns a new string in which all characters in the current instance are converted to lowercase. |
Security Considerations
If you need the lowercase or uppercase version of an operating system identifier, such as a file name, named pipe, or registry key, use the ToLowerInvariant or ToUpperInvariant methods.
The following example defines a string array that contains a single word in a number of languages. The ToLowerInvariant method is used to populate the elements of a parallel array with the case-insensitive version of each word. The Array.Sort<TKey, TValue>(TKey[], TValue[], IComparer<TKey>) method is used to sort the case-sensitive array based on the order of elements in the lowercase array to ensure that elements appear in the same order regardless of language.
using System; public class Example { public static void Main() { string[] words = { "Tuesday", "Salı", "Вторник", "Mardi", "Τρίτη", "Martes", "יום שלישי", "الثلاثاء", "วันอังคาร" }; // Display array in unsorted order. foreach (string word in words) Console.WriteLine(word); Console.WriteLine(); // Create parallel array of words by calling ToLowerInvariant. string[] lowerWords = new string[words.Length]; for (int ctr = words.GetLowerBound(0); ctr <= words.GetUpperBound(0); ctr++) lowerWords[ctr] = words[ctr].ToLowerInvariant(); // Sort the words array based on the order of lowerWords. Array.Sort(lowerWords, words, StringComparer.InvariantCulture); // Display the sorted array. foreach (string word in words) Console.WriteLine(word); } } // The example displays the following output: // Tuesday // Salı // Вторник // Mardi // Τρίτη // Martes // יום שלישי // الثلاثاء // วันอังคาร // // Mardi // Martes // Salı // Tuesday // Τρίτη // Вторник // יום שלישי // الثلاثاء // วันอังคาร
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
In the sample this function seems does nothing: just keeps the string the same.
The Example and the ToLowerInvariant Method
The example uses the ToLowerInvariant method to convert any uppercase characters in the string array to lowercase to perform a case-insensitive sort. The actual lowercased string array, however, is not displayed. Instead, it is stored in a parallel array that is used to sort the primary array, which is then displayed in sorted order.
--Ron Petrusha
Common Language Runtime User Education
Microsoft Corporation
- 2/10/2012
- Dmitry-Rbiyk
- 2/13/2012
- R Petrusha - MSFT
