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GC.GetGeneration Method (WeakReference)

Returns the current generation number of the target of a specified weak reference.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

public static int GetGeneration (
	WeakReference wo
)
public static int GetGeneration (
	WeakReference wo
)
public static function GetGeneration (
	wo : WeakReference
) : int
Not applicable.

Parameters

wo

A WeakReference that refers to the target object whose generation number is to be determined.

Return Value

The current generation number of the target of wo.

Exception typeCondition

ArgumentException

Garbage collection has already been performed on wo.

The following example demonstrates the use of the GetGeneration method to determine the age of a weak reference object.

using System;

namespace GCGetGenerationWeakExample
{
    public class MyGCCollectClass
    {
        private const long maxGarbage = 1000;
      
        static void Main()
        {
            // Create a strong reference to an object.
            MyGCCollectClass myGCCol = new MyGCCollectClass();

            // Put some objects in memory.
            myGCCol.MakeSomeGarbage();
            
            // Get the generation of managed memory where myGCCol is stored.
            Console.WriteLine("The object is in generation: {0}", GC.GetGeneration(myGCCol));
						
            // Perform a full garbage collection.
            // Because there is a strong reference to myGCCol, it will
            // not be garbage collected.
            GC.Collect();
			
            // Get the generation of managed memory where myGCCol is stored.
            Console.WriteLine("The object is in generation: {0}", GC.GetGeneration(myGCCol));
			
            // Create a WeakReference to myGCCol.
            WeakReference wkref = new WeakReference(myGCCol);
            // Remove the strong reference to myGCCol.
            myGCCol = null;
            
            // Get the generation of managed memory where wkref is stored.
            Console.WriteLine("The WeakReference to the object is in generation: {0}", GC.GetGeneration(wkref));
			
            // Perform another full garbage collection.
            // A WeakReference will not survive a garbage collection.
            GC.Collect();
		
            // Try to get the generation of managed memory where wkref is stored.
            // Because it has been collected, an exception will be thrown.
            try
            {
                Console.WriteLine("The WeakReference to the object is in generation: {0}", GC.GetGeneration(wkref));
                Console.Read();
            }
            catch(Exception e)
            {
                Console.WriteLine("The WeakReference to the object has been garbage collected: '{0}'", e);
                Console.Read();
            }
        }

        void MakeSomeGarbage()
        {
            Version vt;

            for(int i = 0; i < maxGarbage; i++)
            {
                // Create objects and release them to fill up memory
                // with unused objects.
                vt = new Version();
            }
        }
    }
}

package GCGetGenerationWeakExample ; 

import System.* ;

public class MyGCCollectClass
{
    private static final long maxGarbage = 1000;

    public static void main(String[] args)
    {
        // Create a strong reference to an object.
        MyGCCollectClass myGCCol = new MyGCCollectClass();

        // Put some objects in memory.
        myGCCol.MakeSomeGarbage();

        // Get the generation of managed memory where myGCCol is stored.
        Console.WriteLine("The object is in generation: {0}", 
            System.Convert.ToString(GC.GetGeneration(myGCCol)));

        // Perform a full garbage collection.
        // Because there is a strong reference to myGCCol, it will
        // not be garbage collected.
        GC.Collect();

        // Get the generation of managed memory where myGCCol is stored.
        Console.WriteLine("The object is in generation: {0}", 
            System.Convert.ToString(GC.GetGeneration(myGCCol)));

        // Create a WeakReference to myGCCol.
        WeakReference wkRef = new WeakReference(myGCCol);

        // Remove the strong reference to myGCCol.
        myGCCol = null;

        // Get the generation of managed memory where wkRef is stored.
        Console.WriteLine("The WeakReference to the object is in " 
            + "generation: {0}",
            System.Convert.ToString(GC.GetGeneration(wkRef)));

        // Perform another full garbage collection.
        // A WeakReference will not survive a garbage collection.
        GC.Collect();

        // Try to get the generation of managed memory where wkRef is stored.
        // Because it has been collected, an exception will be thrown.
        try {
            Console.WriteLine("The WeakReference to the object is in "
                +"generation: {0}",
                System.Convert.ToString(GC.GetGeneration(wkRef)));
            Console.Read();
        }
        catch (System.Exception e) {
            Console.WriteLine(
                "The WeakReference to the object has been garbage collected:" 
                + "'{0}'", e);
            Console.Read();
        }
    } //main

    void MakeSomeGarbage()
    {
        Version vt;

        for (int i = 0; i < maxGarbage; i++) {
            // Create objects and release them to fill up memory
            // with unused objects.
            vt = new Version();
        }
    } //MakeSomeGarbage
} //MyGCCollectClass

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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