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

定義

指定した String への参照を取得します。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

パラメーター

str
String String String String

インターン プールから検索する文字列。The string to search for in the intern pool.

戻り値

str が共通言語ランタイムのインターン プール内にある場合は、それへの参照。それ以外の場合は nullA reference to str if it is in the common language runtime intern pool; otherwise, null.

例外

次の例では、リテラル文字列がコンパイラによって自動的に隔離されてことを示します。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.

注釈

共通言語ランタイムの一意のインスタンスと同様に、プログラムで宣言されている各リテラルの一意の文字列定数の 1 つのインスタンスを含むインターン プールと呼ばれる、テーブルを自動的に維持するStringプログラムで呼び出すことによって追加します。Internメソッド。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.

インターン プールからは、文字列ストレージを節約できます。The intern pool conserves string storage. いくつかの変数にリテラル文字列定数を割り当てると、各変数は設定のいくつかの異なるインスタンスを参照する代わりに、インターン プール内の同じ定数を参照するString同一の値があります。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.

このメソッドを検索strインターン プールから。This method looks up str in the intern pool. 場合strが既にがそのインスタンスへの参照が返されます。 それ以外の場合、nullが返されます。If str has already been interned, a reference to that instance is returned; otherwise, null is returned.

このメソッドを比較、Internメソッド。Compare this method to the Intern method.

このメソッドは、ブール値を返しません。This method does not return a Boolean value. 特定の文字列がインターン プールに存在するかどうかを示すブール値の目的であるため、メソッドを呼び出す場合、次のコードを使用できます。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.

注意

以降、.NET Framework version 2.0 では、オーバーライドできますインターン プールからの使用を使用する場合、 Ngen.exe (ネイティブ イメージ ジェネレーター)ローカル コンピューター上のネイティブ イメージ キャッシュにアセンブリをインストールします。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. 詳細については、パフォーマンスに関する考慮事項は、「解説」を参照してください、Internプロパティ。For more information, see Performance Considerations in the Remarks section for the Intern property.

適用対象

こちらもご覧ください