String.ToLower String.ToLower String.ToLower String.ToLower Method

定義

傳回此字串轉換為小寫的版本。Returns a copy of this string converted to lowercase.

多載

ToLower(CultureInfo) ToLower(CultureInfo) ToLower(CultureInfo) ToLower(CultureInfo)

使用指定之文化特性的大小寫規則,傳回這個字串轉換成小寫的複本。Returns a copy of this string converted to lowercase, using the casing rules of the specified culture.

ToLower() ToLower() ToLower() ToLower()

傳回此字串轉換為小寫的版本。Returns a copy of this string converted to lowercase.

ToLower(CultureInfo) ToLower(CultureInfo) ToLower(CultureInfo) ToLower(CultureInfo)

使用指定之文化特性的大小寫規則,傳回這個字串轉換成小寫的複本。Returns a copy of this string converted to lowercase, using the casing rules of the specified culture.

public:
 System::String ^ ToLower(System::Globalization::CultureInfo ^ culture);
public string ToLower (System.Globalization.CultureInfo culture);
member this.ToLower : System.Globalization.CultureInfo -> string
Public Function ToLower (culture As CultureInfo) As String

參數

culture
CultureInfo CultureInfo CultureInfo CultureInfo

提供文化特性大小寫規則的物件。An object that supplies culture-specific casing rules.

傳回

目前字串的小寫對應項。The lowercase equivalent of the current string.

例外狀況

範例

下列範例會使用英文(美國)和土耳其文-土耳其文化特性,將兩個大寫字元字串轉換成小寫字元,然後比較小寫字串。The following example converts two strings of uppercase characters to lowercase characters using the English-United States and Turkish-Turkey cultures, then compares the lowercase strings. 大寫字串完全相同,不同之處在于一個字串中每個出現的 Unicode 拉丁大寫字母 I,另一個字串包含上面加上點的拉丁大寫字母 I。The uppercase strings are identical except that for each occurrence of the Unicode LATIN CAPITAL LETTER I in one string, the other string contains LATIN CAPITAL LETTER I WITH DOT ABOVE.

// Sample for String::ToLower(CultureInfo)
using namespace System;
using namespace System::Globalization;
void CodePoints( String^ title, String^ s )
{
   Console::Write( "{0}The code points in {1} are: {0}", Environment::NewLine, title );
   System::Collections::IEnumerator^ myEnum = s->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      UInt16 u =  safe_cast<Char>(myEnum->Current);
      Console::Write( "{0:x4} ", u );
   }

   Console::WriteLine();
}

int main()
{
   String^ str1 = "INDIGO";
   
   // str2 = str1, except each 'I' is '\u0130' (Unicode LATIN CAPITAL I WITH DOT ABOVE).
   array<Char>^temp = {L'\u0130',L'N',L'D',L'\u0130',L'G',L'O'};
   String^ str2 = gcnew String( temp );
   String^ str3;
   String^ str4;
   Console::WriteLine();
   Console::WriteLine( "str1 = '{0}'", str1 );
   Console::WriteLine();
   Console::WriteLine( "str1 is {0} to str2.", ((0 == String::CompareOrdinal( str1, str2 )) ? (String^)"equal" : "not equal") );
   CodePoints( "str1", str1 );
   CodePoints( "str2", str2 );
   Console::WriteLine();
   
   // str3 is a lower case copy of str2, using English-United States culture.
   Console::WriteLine( "str3 = Lower case copy of str2 using English-United States culture." );
   str3 = str2->ToLower( gcnew CultureInfo( "en-US",false ) );
   
   // str4 is a lower case copy of str2, using Turkish-Turkey culture.
   Console::WriteLine( "str4 = Lower case copy of str2 using Turkish-Turkey culture." );
   str4 = str2->ToLower( gcnew CultureInfo( "tr-TR",false ) );
   
   // Compare the code points in str3 and str4.
   Console::WriteLine();
   Console::WriteLine( "str3 is {0} to str4.", ((0 == String::CompareOrdinal( str3, str4 )) ? (String^)"equal" : "not equal") );
   CodePoints( "str3", str3 );
   CodePoints( "str4", str4 );
}

/*
This example produces the following results:

str1 = 'INDIGO'

str1 is not equal to str2.

The code points in str1 are:
0049 004e 0044 0049 0047 004f

The code points in str2 are:
0130 004e 0044 0130 0047 004f

str3 = Lower case copy of str2 using English-United States culture.
str4 = Lower case copy of str2 using Turkish-Turkey culture.

str3 is equal to str4.

The code points in str3 are:
0069 006e 0064 0069 0067 006f

The code points in str4 are:
0069 006e 0064 0069 0067 006f
*/
// Sample for String.ToLower(CultureInfo)

using System;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    String str1 = "INDIGO";
    // str2 = str1, except each 'I' is '\u0130' (Unicode LATIN CAPITAL I WITH DOT ABOVE).
    String str2 = new String(new Char[] {'\u0130', 'N', 'D', '\u0130', 'G', 'O'});
    String str3, str4;

    Console.WriteLine();
    Console.WriteLine("str1 = '{0}'", str1);

    Console.WriteLine();
    Console.WriteLine("str1 is {0} to str2.", 
         ((0 == String.CompareOrdinal(str1, str2)) ? "equal" : "not equal"));
    CodePoints("str1", str1);
    CodePoints("str2", str2);

    Console.WriteLine();
    // str3 is a lower case copy of str2, using English-United States culture.
    Console.WriteLine("str3 = Lower case copy of str2 using English-United States culture.");
    str3 = str2.ToLower(new CultureInfo("en-US", false));

    // str4 is a lower case copy of str2, using Turkish-Turkey culture.
    Console.WriteLine("str4 = Lower case copy of str2 using Turkish-Turkey culture.");
    str4 = str2.ToLower(new CultureInfo("tr-TR", false));

    // Compare the code points in str3 and str4.
    Console.WriteLine();
    Console.WriteLine("str3 is {0} to str4.", 
         ((0 == String.CompareOrdinal(str3, str4)) ? "equal" : "not equal"));
    CodePoints("str3", str3);
    CodePoints("str4", str4);
    }

    public static void CodePoints(String title, String s)
    {
    Console.Write("{0}The code points in {1} are: {0}", Environment.NewLine, title);
    foreach (ushort u in s)
      Console.Write("{0:x4} ", u);
    Console.WriteLine();
    }
}
/*
This example produces the following results:

str1 = 'INDIGO'

str1 is not equal to str2.

The code points in str1 are:
0049 004e 0044 0049 0047 004f

The code points in str2 are:
0130 004e 0044 0130 0047 004f

str3 = Lower case copy of str2 using English-United States culture.
str4 = Lower case copy of str2 using Turkish-Turkey culture.

str3 is equal to str4.

The code points in str3 are:
0069 006e 0064 0069 0067 006f

The code points in str4 are:
0069 006e 0064 0069 0067 006f
*/
' Sample for String.ToLower(CultureInfo)
Imports System.Globalization

Class Sample
   Public Shared Sub Main()
      Dim str1 As [String] = "INDIGO"
      ' str2 = str1, except each 'I' is '\u0130' (Unicode LATIN CAPITAL I WITH DOT ABOVE).
      Dim str2 As New [String](New [Char]() {ChrW(&H0130), "N"c, "D"c, ChrW(&H0130), "G"c, "O"c})
      Dim str3, str4 As [String]

      Console.WriteLine()
      Console.WriteLine("str1 = '{0}'", str1)

      Console.WriteLine()
      Console.WriteLine("str1 is {0} to str2.", _
                         IIf(0 = [String].CompareOrdinal(str1, str2), "equal", "not equal"))
      CodePoints("str1", str1)
      CodePoints("str2", str2)

      Console.WriteLine()
      ' str3 is a lower case copy of str2, using English-United States culture.
      Console.WriteLine("str3 = Lower case copy of str2 using English-United States culture.")
      str3 = str2.ToLower(New CultureInfo("en-US", False))

      ' str4 is a lower case copy of str2, using Turkish-Turkey culture.
      Console.WriteLine("str4 = Lower case copy of str2 using Turkish-Turkey culture.")
      str4 = str2.ToLower(New CultureInfo("tr-TR", False))

      ' Compare the code points in str3 and str4.
      Console.WriteLine()
      Console.WriteLine("str3 is {0} to str4.", _
                         IIf(0 = [String].CompareOrdinal(str3, str4), "equal", "not equal"))
      CodePoints("str3", str3)
      CodePoints("str4", str4)
   End Sub

   Public Shared Sub CodePoints(title As [String], s As [String])
      Console.Write("{0}The code points in {1} are: {0}", Environment.NewLine, title)
      Dim c As Char
      For Each c In  s
         Console.Write("{0:x4} ", AscW(c))
      Next c
      Console.WriteLine()
   End Sub
End Class
'
'str1 = 'INDIGO'
'
'str1 is not equal to str2.
'
'The code points in str1 are:
'0049 004e 0044 0049 0047 004f
'
'The code points in str2 are:
'0130 004e 0044 0130 0047 004f
'
'str3 = Lower case copy of str2 using English-United States culture.
'str4 = Lower case copy of str2 using Turkish-Turkey culture.
'
'str3 is equal to str4.
'
'The code points in str3 are:
'0069 006e 0064 0069 0067 006f
'
'The code points in str4 are:
'0069 006e 0064 0069 0067 006f

備註

culture參數所指定之文化特性的大小寫規則,決定了字串大小寫變更的方式。The casing rules of the culture specified by the culture parameter determine the way the case of the string is changed.

注意

這個方法不會修改目前實例的值。This method does not modify the value of the current instance. 相反地,它會傳回新的字串,其中目前實例中的所有字元都會轉換成小寫。Instead, it returns a new string in which all characters in the current instance are converted to lowercase.

安全性考量Security Considerations

如果您將以外ToLower(CultureInfo) CultureInfo CultureInfo.InvariantCulture的物件傳遞給方法,則大小寫作業會將特定文化特性的規則納入考慮。If you pass the ToLower(CultureInfo) method a CultureInfo object other than CultureInfo.InvariantCulture, the casing operation will take culture-specific rules into account. 如果您需要作業系統識別碼的小寫或大寫版本,例如檔案名、具名管道或登錄機碼,請使用ToLowerInvariantToUpperInvariant方法。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 method. 這會在每個文化特性中產生相同的結果,並更有效率地執行。This produces the same result in every culture and performs more efficiently.

另請參閱

ToLower() ToLower() ToLower() ToLower()

傳回此字串轉換為小寫的版本。Returns a copy of this string converted to lowercase.

public:
 System::String ^ ToLower();
public string ToLower ();
member this.ToLower : unit -> string
Public Function ToLower () As String

傳回

小寫的字串。A string in lowercase.

範例

下列範例會將數個混合大小寫字串轉換成小寫。The following example converts several mixed case strings to lowercase.

using namespace System;
using namespace System::Collections;
int main()
{
   array<String^>^info = {"Name","Title","Age","Location","Gender"};
   Console::WriteLine( "The initial values in the array are:" );
   IEnumerator^ myEnum = info->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      String^ s = safe_cast<String^>(myEnum->Current);
      Console::WriteLine( s );
   }

   Console::WriteLine( " {0}The lowercase of these values is:", Environment::NewLine );
   IEnumerator^ myEnum1 = info->GetEnumerator();
   while ( myEnum1->MoveNext() )
   {
      String^ s = safe_cast<String^>(myEnum1->Current);
      Console::WriteLine( s->ToLower() );
   }

   Console::WriteLine( " {0}The uppercase of these values is:", Environment::NewLine );
   IEnumerator^ myEnum2 = info->GetEnumerator();
   while ( myEnum2->MoveNext() )
   {
      String^ s = safe_cast<String^>(myEnum2->Current);
      Console::WriteLine( s->ToUpper() );
   }
}
// The example displays the following output:
//       The initial values in the array are:
//       Name
//       Title
//       Age
//       Location
//       Gender
//       
//       The lowercase of these values is:
//       name
//       title
//       age
//       location
//       gender
//       
//       The uppercase of these values is:
//       NAME
//       TITLE
//       AGE
//       LOCATION
//       GENDER
using System;

public class ToLowerTest {
    public static void Main() {

        string [] info = {"Name", "Title", "Age", "Location", "Gender"};

        Console.WriteLine("The initial values in the array are:");
        foreach (string s in info)
            Console.WriteLine(s);

        Console.WriteLine("{0}The lowercase of these values is:", Environment.NewLine);        

        foreach (string s in info)
            Console.WriteLine(s.ToLower());

        Console.WriteLine("{0}The uppercase of these values is:", Environment.NewLine);        

        foreach (string s in info)
            Console.WriteLine(s.ToUpper());
    }
}
// The example displays the following output:
//       The initial values in the array are:
//       Name
//       Title
//       Age
//       Location
//       Gender
//       
//       The lowercase of these values is:
//       name
//       title
//       age
//       location
//       gender
//       
//       The uppercase of these values is:
//       NAME
//       TITLE
//       AGE
//       LOCATION
//       GENDER
Public Class ToLowerTest
    
    Public Shared Sub Main()
        Dim info As String() = {"Name", "Title", "Age", "Location", "Gender"}
        
        Console.WriteLine("The initial values in the array are:")

        Dim s As String
        For Each s In info
            Console.WriteLine(s)
        Next 

        Console.WriteLine("{0}The lowercase of these values is:", Environment.NewLine)

        For Each s In info
            Console.WriteLine(s.ToLower())
        Next 

        Console.WriteLine("{0}The uppercase of these values is:", Environment.NewLine)

        For Each s In  info
            Console.WriteLine(s.ToUpper())
        Next 
    End Sub 
End Class 
' The example displays the following output:
'       The initial values in the array are:
'       Name
'       Title
'       Age
'       Location
'       Gender
'       
'       The lowercase of these values is:
'       name
'       title
'       age
'       location
'       gender
'       
'       The uppercase of these values is:
'       NAME
'       TITLE
'       AGE
'       LOCATION
'       GENDER

備註

這個方法會考慮目前文化特性的大小寫規則。This method takes into account the casing rules of the current culture.

注意

這個方法不會修改目前實例的值。This method does not modify the value of the current instance. 相反地,它會傳回新的字串,其中目前實例中的所有字元都會轉換成小寫。Instead, it returns a new string in which all characters in the current instance are converted to lowercase.

安全性考量Security Considerations

呼叫ToLower()方法所產生的大小寫運算,會將目前文化特性的大小寫慣例納入考慮。The casing operation that results from calling the ToLower() method takes the casing conventions of the current culture into account. 如果您需要作業系統識別碼的小寫或大寫版本,例如檔案名、具名管道或登錄機碼,請使用ToLowerInvariantToUpperInvariant方法。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. 這會在每個文化特性(不同于ToLower()方法)中產生相同的結果,並更有效率地執行。This produces the same result in every culture (unlike the ToLower() method) and performs more efficiently.

給呼叫者的注意事項

使用字串的最佳作法中所述,我們建議您避免呼叫替代預設值的字串大小寫方法,而改為呼叫需要明確指定參數的方法。As explained in Best Practices for Using Strings, we recommend that you avoid calling string casing methods that substitute default values and instead call methods that require parameters to be explicitly specified. 若要使用目前文化特性的大小寫慣例,將字元轉換成小寫,請ToLower(CultureInfo)呼叫其culture參數CurrentCulture值為的方法多載。To convert a character to lowercase by using the casing conventions of the current culture, call the ToLower(CultureInfo) method overload with a value of CurrentCulture for its culture parameter.

另請參閱

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