String.IsInterned(String) String.IsInterned(String) String.IsInterned(String) String.IsInterned(String) Method

Definição

Recupera uma referência a um String especificado.Retrieves a reference to a specified String.

public:
 static System::String ^ IsInterned(System::String ^ str);
public static string IsInterned (string str);
static member IsInterned : string -> string
Public Shared Function IsInterned (str As String) As String

Parâmetros

str
String String String String

A cadeia de caracteres para pesquisar no pool interno.The string to search for in the intern pool.

Retornos

Uma referência a str se ele estiver no pool interno de Common Language Runtime; caso contrário, null.A reference to str if it is in the common language runtime intern pool; otherwise, null.

Exceções

Exemplos

O exemplo a seguir demonstra que as cadeias de caracteres literais sejam internalizadas automaticamente pelo compilador.The following example demonstrates that literal strings are interned automatically by the compiler.

// Sample for String::IsInterned(String)
using namespace System;
using namespace System::Text;
using namespace System::Runtime::CompilerServices;

// In the .NET Framework 2.0 the following attribute declaration allows you to 
// avoid the use of the interning when you use NGEN.exe to compile an assembly 
// to the native image cache.
[assembly:CompilationRelaxations(CompilationRelaxations::NoStringInterning)];
void Test( int sequence, String^ str )
{
   Console::Write( "{0} The string '", sequence );
   String^ strInterned = String::IsInterned( str );
   if ( strInterned == nullptr )
      Console::WriteLine( "{0}' is not interned.", str );
   else
      Console::WriteLine( "{0}' is interned.", strInterned );
}

int main()
{
   
   // String str1 is known at compile time, and is automatically interned.
   String^ str1 = "abcd";
   
   // Constructed string, str2, is not explicitly or automatically interned.
   String^ str2 = (gcnew StringBuilder)->Append( "wx" )->Append( "yz" )->ToString();
   Console::WriteLine();
   Test( 1, str1 );
   Test( 2, str2 );
}

//This example produces the following results:

//1) The string, 'abcd', is interned.
//2) The string, 'wxyz', is not interned.

//If you use NGEN.exe to compile the assembly to the native image cache, this
//example produces the following results:

//1) The string, 'abcd', is not interned.
//2) The string, 'wxyz', is not interned.

// Sample for String.IsInterned(String)
using System;
using System.Text;
using System.Runtime.CompilerServices;

// In the .NET Framework 2.0 the following attribute declaration allows you to 
// avoid the use of the interning when you use NGEN.exe to compile an assembly 
// to the native image cache.
[assembly: CompilationRelaxations(CompilationRelaxations.NoStringInterning)]
class Sample
{
    public static void Main()
    {
        // String str1 is known at compile time, and is automatically interned.
        String str1 = "abcd";

        // Constructed string, str2, is not explicitly or automatically interned.
        String str2 = new StringBuilder().Append("wx").Append("yz").ToString();
        Console.WriteLine();
        Test(1, str1);
        Test(2, str2);
    }

    public static void Test(int sequence, String str)
    {
        Console.Write("{0}) The string, '", sequence);
        String strInterned = String.IsInterned(str);
        if (strInterned == null)
            Console.WriteLine("{0}', is not interned.", str);
        else
            Console.WriteLine("{0}', is interned.", strInterned);
    }
}

//This example produces the following results:

//1) The string, 'abcd', is interned.
//2) The string, 'wxyz', is not interned.

//If you use NGEN.exe to compile the assembly to the native image cache, this
//example produces the following results:

//1) The string, 'abcd', is not interned.
//2) The string, 'wxyz', is not interned.

' Sample for String.IsInterned(String)
Imports System
Imports System.Text
Imports System.Runtime.CompilerServices

' In the .NET Framework 2.0 the following attribute declaration allows you to 
' avoid the use of the interning when you use NGEN.exe to compile an assembly 
' to the native image cache.
<Assembly: CompilationRelaxations(CompilationRelaxations.NoStringInterning)> 
Class Sample
    Public Shared Sub Main()
        ' String str1 is known at compile time, and is automatically interned.
        Dim str1 As [String] = "abcd"

        ' Constructed string, str2, is not explicitly or automatically interned.
        Dim str2 As [String] = New StringBuilder().Append("wx").Append("yz").ToString()
        Console.WriteLine()
        Test(1, str1)
        Test(2, str2)
    End Sub 'Main

    Public Shared Sub Test(ByVal sequence As Integer, ByVal str As [String])
        Console.Write("{0}) The string, '", sequence)
        Dim strInterned As [String] = [String].IsInterned(str)
        If strInterned Is Nothing Then
            Console.WriteLine("{0}', is not interned.", str)
        Else
            Console.WriteLine("{0}', is interned.", strInterned)
        End If
    End Sub 'Test
End Class 'Sample '

'This example produces the following results:

'1) The string, 'abcd', is interned.
'2) The string, 'wxyz', is not interned.

'If you use NGEN.exe to compile the assembly to the native image cache, this
'example produces the following results:

'1) The string, 'abcd', is not interned.
'2) The string, 'wxyz', is not interned.

Comentários

O common language runtime mantém automaticamente uma tabela, chamada pool interno, que contém uma única instância de cada constante de literal de cadeia de caracteres exclusiva declarado em um programa, bem como qualquer instância exclusiva do String você adicionar programaticamente chamando o Intern método.The common language runtime automatically maintains a table, called the intern pool, which contains a single instance of each unique literal string constant declared in a program, as well as any unique instance of String you add programmatically by calling the Intern method.

Armazenamento de cadeia de caracteres preserva a pool interno.The intern pool conserves string storage. Se você atribuir uma constante de cadeia de caracteres literal a diversas variáveis, cada variável é definida para referenciar a mesma constante no pool interno em vez de referenciar várias instâncias diferentes do String que têm valores idênticos.If you assign a literal string constant to several variables, each variable is set to reference the same constant in the intern pool instead of referencing several different instances of String that have identical values.

Este método pesquisa str no pool interno.This method looks up str in the intern pool. Se str já foi internalizadas, uma referência a essa instância é retornado; caso contrário, null será retornado.If str has already been interned, a reference to that instance is returned; otherwise, null is returned.

Compare este método para o Intern método.Compare this method to the Intern method.

Esse método não retorna um valor booliano.This method does not return a Boolean value. Se você chamar o método porque você deseja que um valor booliano que indica se uma determinada cadeia de caracteres é internalizada, você pode usar código como o seguinte.If you call the method because you want a Boolean value that indicates whether a particular string is interned, you can use code such as the following.

using System;

public class Example
{
   public static void Main()
   {
      string str1 = "a";
      string str2 = str1 + "b";
      string str3 = str2 + "c";
      string[] strings = { "value", "part1" + "_" + "part2", str3, 
                           String.Empty, null };
      foreach (var value in strings) {
         if (value == null) continue;
         
         bool interned = String.IsInterned(value) != null;
         if (interned)
            Console.WriteLine("'{0}' is in the string intern pool.", 
                              value);
         else
            Console.WriteLine("'{0}' is not in the string intern pool.",
                              value);                      
      }
   }
}
// The example displays the following output:
//       'value' is in the string intern pool.
//       'part1_part2' is in the string intern pool.
//       'abc' is not in the string intern pool.
//       '' is in the string intern pool.
Module Example
   Public Sub Main()
      Dim str1 As String = "a"
      Dim str2 As String = str1 + "b"
      Dim str3 As String = str2 + "c"
      Dim strings() As String = { "value", "part1" + "_" + "part2", str3, 
                                  String.Empty, Nothing }
      For Each value In strings
         If value Is Nothing Then Continue For
         
         Dim interned As Boolean = (String.IsInterned(value) IsNot Nothing)
         If interned Then
            Console.WriteLine("'{0}' is in the string intern pool.", 
                              value)
         Else
            Console.WriteLine("'{0}' is not in the string intern pool.",
                              value)                      
         End If
      Next
   End Sub
End Module
' The example displays the following output:
'       'value' is in the string intern pool.
'       'part1_part2' is in the string intern pool.
'       'abc' is not in the string intern pool.
'       '' is in the string intern pool.

Observação

Começando com o .NET Framework versão 2.0, você pode substituir o uso do pool interno de quando você usa o Ngen.exe (Native Image Generator) para instalar um assembly no cache de imagem nativa em um computador local.Starting with the .NET Framework version 2.0, you can override the use of the intern pool when you use the Ngen.exe (Native Image Generator) to install an assembly to the native image cache on a local computer. Para obter mais informações, consulte Considerações de desempenho na seção comentários para o Intern propriedade.For more information, see Performance Considerations in the Remarks section for the Intern property.

Aplica-se a

Veja também