String.ToLowerInvariant Method

public:
 System::String ^ ToLowerInvariant();

public string ToLowerInvariant();

member this.ToLowerInvariant : unit -> string

Public Function ToLowerInvariant () As String

Returns

The lowercase equivalent of the current string.

Examples

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

open System

let words = 
 [| "Tuesday"; "Salı"; "Вторник"; "Mardi" 
 "Τρίτη"; "Martes"; "יום שלישי" 
 "الثلاثاء"; "วันอังคาร" |]
// Display array in unsorted order.
for word in words do
 printfn $"{word}"
printfn ""

// Create parallel array of words by calling ToLowerInvariant.
let lowerWords = 
 words |> Array.map (fun x -> x.ToLowerInvariant())

// Sort the words array based on the order of lowerWords.
Array.Sort(lowerWords, words, StringComparer.InvariantCulture)

// Display the sorted array.
for word in words do
 printfn $"{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

Module Example
 Public Sub Main()
 Dim words() As String = { "Tuesday", "Salı", "Вторник", "Mardi", _
 "Τρίτη", "Martes", "יום שלישי", _
 "الثلاثاء", "วันอังคาร" }
 ' Display array in unsorted order.
 For Each word As String In words
 Console.WriteLine(word)
 Next
 Console.WriteLine()

 ' Create parallel array of words by calling ToLowerInvariant.
 Dim lowerWords(words.Length - 1) As String
 For ctr As Integer = words.GetLowerBound(0) To words.GetUpperBound(0)
 lowerWords(ctr) = words(ctr).ToLowerInvariant()
 Next
 
 ' Sort the words array based on the order of lowerWords.
 Array.Sort(lowerWords, words, StringComparer.InvariantCulture)
 
 ' Display the sorted array.
 For Each word As String In words
 Console.WriteLine(word)
 Next
 End Sub
End Module
' 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

Remarks

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 the CultureInfo.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.

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.

See also

• ToUpperInvariant()
• ToLower(CultureInfo)
• ToLower()
• InvariantCulture