String.IsInterned(String) Metoda
Definice
Důležité
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Načte odkaz na zadanou Stringhodnotu .
public:
static System::String ^ IsInterned(System::String ^ str);
public static string? IsInterned (string str);
public static string IsInterned (string str);
static member IsInterned : string -> string
Public Shared Function IsInterned (str As String) As String
Parametry
- str
- String
Řetězec, který chcete vyhledat ve fondu internů.
Návraty
Odkaz na str
to, jestli je ve fondu internů modulu CLR (Common Language Runtime), jinak . null
Výjimky
str
je null
.
Příklady
Následující příklad ukazuje, že řetězcové literály jsou interovány automaticky kompilátorem.
// 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)
open System
open System.Text
open 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)>]
do ()
let test sequence str =
printf $"%d{sequence}) The string, '"
let strInterned = String.IsInterned str
if isNull strInterned then
printfn $"{str}', is not interned."
else
printfn $"{strInterned}', is interned."
// String str1 is known at compile time, and is automatically interned.
let str1 = "abcd"
// Constructed string, str2, is not explicitly or automatically interned.
let str2 = StringBuilder().Append("wx").Append("yz").ToString()
printfn ""
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)
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
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
End Class
'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.
Poznámky
Modul CLR (Common Language Runtime) automaticky udržuje tabulku označovanou jako internový fond, který obsahuje jednu instanci každé jedinečné řetězcové konstanty literálu deklarované v programu a také libovolnou jedinečnou instanci String , kterou přidáte programově voláním Intern metody.
Fond internů šetří úložiště řetězců. Pokud přiřadíte řetězcovou konstantu literálu několika proměnným, každá proměnná je nastavená tak, aby odkazovaly na stejnou konstantu ve fondu internů místo odkazování na několik různých instancí String , které mají stejné hodnoty.
Tato metoda vyhledá str
ve fondu internů. Pokud str
již byla prováznuta, vrátí se odkaz na danou instanci. V opačném případě null
se vrátí.
Porovnejte tuto metodu s metodou Intern .
Tato metoda nevrací logickou hodnotu. Pokud voláte metodu, protože chcete logickou hodnotu, která označuje, jestli je určitý řetězec internovaný, můžete použít kód, například následující.
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.
open System
let str1 = "a"
let str2 = str1 + "b"
let str3 = str2 + "c"
let strings =
[| "value"; "part1" + "_" + "part2"; str3
String.Empty; null |]
for value in strings do
if value <> null then
let interned = String.IsInterned(value) <> null
if interned then
printfn $"'{value}' is in the string intern pool."
else
printfn $"'{value}' is not in the string intern pool."
// 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.
Poznámka
Použití fondu internů můžete přepsat, když použijete Ngen.exe (Generátor nativních imagí) k instalaci sestavení do mezipaměti nativních imagí na místním počítači. Další informace najdete v tématu Důležité informace o výkonu v části Poznámky pro Intern vlastnost.