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GC.Collect Method (Int32, GCCollectionMode)

Forces a garbage collection from generation zero through a specified generation, at a time specified by a GCCollectionMode value.

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

public static void Collect(
	int generation,
	GCCollectionMode mode


Type: System.Int32
The number of the oldest generation that garbage collection can be performed on.
Type: System.GCCollectionMode
One of the GCCollectionMode values.


generation is not valid.


mode is not one of the GCCollectionMode values.

Use the mode parameter to specify whether garbage collection should occur immediately or only if the time is optimal to reclaim objects. Using this method does not guarantee that all inaccessible memory in the specified generation is reclaimed.

To adjust the intrusiveness of garbage collection during critical periods in your application, set the LatencyMode property.

The garbage collector does not collect objects with a generation number higher than specified by the generation parameter. Use the MaxGeneration property to determine the maximum valid value of generation.

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 up to a specified generation of objects, use the GC.Collect(Int32) method overload. When you specify the maximum generation, all objects are collected.

The following example forces a garbage collection for generation 2 objects with the Optimized setting.

using System;

class Program
    static void Main(string[] args)
        GC.Collect(2, GCCollectionMode.Optimized);

.NET Framework

Supported in: 4, 3.5 SP1, 3.0 SP1, 2.0 SP1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.