FixedAddressValueTypeAttribute Konstruktor

Definisi

Ruang nama:

System.Runtime.CompilerServices

Rakitan:

System.Runtime.dll

Sumber:

FixedAddressValueTypeAttribute.cs

Menginisialisasi instans baru kelas FixedAddressValueTypeAttribute.

public:
 FixedAddressValueTypeAttribute();

public FixedAddressValueTypeAttribute ();

Public Sub New ()

Contoh

Contoh berikut mengilustrasikan penggunaan FixedAddressValueTypeAttribute atribut untuk menyematkan bidang statis dalam memori. Ini mendefinisikan Age struktur dan menginisialisasi dua kelas yang memiliki bidang statis jenis Age. Kelas kedua berlaku FixedAddressValueTypeAttribute untuk menyematkan alamat bidang. Sejumlah alokasi memori dibuat sebelum dan sesudah kedua objek ini dibuat dan pengumpul sampah dipanggil. Output dari contoh menunjukkan bahwa meskipun alamat bidang pertama Age telah berubah setelah pengumpulan sampah, alamat bidang yang FixedAddressValueTypeAttribute diterapkan belum.

using System;
using System.Runtime.CompilerServices;

public struct Age {
   public int years;
   public int months;
}

public class FreeClass
{
   public static Age FreeAge;
   
   public static unsafe IntPtr AddressOfFreeAge()
   { 
      fixed (Age* pointer = &FreeAge) 
      { return (IntPtr) pointer; } 
   }
}

public class FixedClass
{
   [FixedAddressValueType]
   public static Age FixedAge;
   
   public static unsafe IntPtr AddressOfFixedAge()
   { 
      fixed (Age* pointer = &FixedAge) 
      { return (IntPtr) pointer; } 
   }   
}

public class Example
{
   public static void Main()
   {
      AllocateMemory();
      
      // Get addresses of static Age fields.
      IntPtr freePtr1 = FreeClass.AddressOfFreeAge();
      AllocateMemory();
      
      IntPtr fixedPtr1 = FixedClass.AddressOfFixedAge();
      AllocateMemory();

      // Garbage collection.
      GC.Collect();
      GC.WaitForPendingFinalizers();
      
      // Get addresses of static Age fields after garbage collection.
      IntPtr freePtr2 = FreeClass.AddressOfFreeAge();
      IntPtr fixedPtr2 = FixedClass.AddressOfFixedAge();
        
      // Display addresses before and after garbage collection
      Console.WriteLine("Normal static: {0} -> {1}", freePtr1, freePtr2);
      Console.WriteLine("Pinned static:  {0} -> {1}", fixedPtr1, fixedPtr2);  
   }

   // Allocate memory for 100,000 objects.
   static public void AllocateMemory()
   {
      for (int ctr = 0; ctr <= 100000; ctr++)
      {
         object o = new object();      
      }
   }
}
// The example displays output similar to the following:
//       Normal static: 19932420 -> 19863704
//       Pinned static:  19985508 -> 19985508