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GC.Collect Method (Int32)

Forces an immediate garbage collection from generation zero through a specified generation.

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

public static void Collect (
	int generation
)
public static void Collect (
	int generation
)
public static function Collect (
	generation : int
)
Not applicable.

Parameters

generation

The number of the oldest generation that garbage collection can be performed on.

Exception typeCondition

ArgumentOutOfRangeException

generation is less than 0.

Use this method to try to reclaim memory that is inaccessible. However, using this method does not guarantee that all inaccessible memory in the specified generation is reclaimed.

If object aging is implemented, the garbage collector does not collect objects with a generation number that is higher than the specified generation. If object aging is not implemented, the garbage collector considers all objects during the garbage collection.

Use the MaxGeneration property to determine the maximum valid value of the generation parameter.

To have the garbage collector consider all objects regardless of their generation, use the version of this method that takes no parameters. To have the garbage collector reclaim objects based on a GCCollectionMode setting, use the System.GC.Collect(System.Int32,System.GCCollectionMode) method overload.

The following example demonstrates how to use the Collect method to perform a collection on individual layers of memory. The code generates a number of unused objects, and then calls the Collect method to clean them from memory.

using System;

namespace GCCollectIntExample
{
    class MyGCCollectClass
    {
        private const long maxGarbage = 1000;
      
        static void Main()
        {
            MyGCCollectClass myGCCol = new MyGCCollectClass();

            // Determine the maximum number of generations the system
	    // garbage collector currently supports.
            Console.WriteLine("The highest generation is {0}", GC.MaxGeneration);
            
            myGCCol.MakeSomeGarbage();

            // Determine which generation myGCCol object is stored in.
            Console.WriteLine("Generation: {0}", GC.GetGeneration(myGCCol));
            
            // Determine the best available approximation of the number 
	    // of bytes currently allocated in managed memory.
            Console.WriteLine("Total Memory: {0}", GC.GetTotalMemory(false));
            
            // Perform a collection of generation 0 only.
            GC.Collect(0);
            
            // Determine which generation myGCCol object is stored in.
            Console.WriteLine("Generation: {0}", GC.GetGeneration(myGCCol));
            
            Console.WriteLine("Total Memory: {0}", GC.GetTotalMemory(false));
            
            // Perform a collection of all generations up to and including 2.
            GC.Collect(2);
            
            // Determine which generation myGCCol object is stored in.
            Console.WriteLine("Generation: {0}", GC.GetGeneration(myGCCol));
            Console.WriteLine("Total Memory: {0}", GC.GetTotalMemory(false));
            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 GCCollectIntExample; 

import System.* ;

class MyGCCollectClass
{
    private static final long maxGarbage = 1000;

    public static void main(String[] args)
    {
        MyGCCollectClass myGCCol = new MyGCCollectClass();

        // Determine the maximum number of generations the system
        // garbage collector currently supports.
        Console.WriteLine("The highest generation is {0}", 
            System.Convert.ToString(GC.get_MaxGeneration()));
        myGCCol.MakeSomeGarbage();

        // Determine which generation myGCCol object is stored in.
        Console.WriteLine("Generation: {0}", 
            System.Convert.ToString(GC.GetGeneration(myGCCol)));

        // Determine the best available approximation of the number 
        // of bytes currently allocated in managed memory.
        Console.WriteLine("Total Memory: {0}", 
            System.Convert.ToString(GC.GetTotalMemory(false)));

        // Perform a collection of generation 0 only.
        GC.Collect(0);

        // Determine which generation myGCCol object is stored in.
        Console.WriteLine("Generation: {0}", 
            System.Convert.ToString(GC.GetGeneration(myGCCol)));
        Console.WriteLine("Total Memory: {0}", 
            System.Convert.ToString(GC.GetTotalMemory(false)));

        // Perform a collection of all generations up to and including 2.
        GC.Collect(2);

        // Determine which generation myGCCol object is stored in.
        Console.WriteLine("Generation: {0}", 
            System.Convert.ToString(GC.GetGeneration(myGCCol)));
        Console.WriteLine("Total Memory: {0}", 
            System.Convert.ToString(GC.GetTotalMemory(false)));
        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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