GC.Collect Method ()

 

Forces an immediate garbage collection of all generations.

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

Public Shared Sub Collect

Use this method to try to reclaim all memory that is inaccessible. It performs a blocking garbage collection of all generations.

All objects, regardless of how long they have been in memory, are considered for collection; however, objects that are referenced in managed code are not collected. Use this method to force the system to try to reclaim the maximum amount of available memory.

Starting with the .NET Framework 4.5.1, you can compact the large object heap (LOH) by setting the GCSettings.LargeObjectHeapCompactionMode property to GCLargeObjectHeapCompactionMode.CompactOnce before calling the Collect method, as the following example illustrates.

GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce
GC.Collect()      

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

Class MyGCCollectClass
     Private Const maxGarbage As Integer = 1000

     Shared Sub Main()
         'Put some objects in memory.
         MyGCCollectClass.MakeSomeGarbage()
         Console.WriteLine("Memory used before collection:       {0:N0}", 
                           GC.GetTotalMemory(False))

         'Collect all generations of memory.
         GC.Collect()
         Console.WriteLine("Memory used after full collection:   {0:N0}", 
                           GC.GetTotalMemory(True))
     End Sub

     Shared Sub MakeSomeGarbage()
         Dim vt As Version

         Dim i As Integer
         For i = 0 To maxGarbage - 1
             'Create objects and release them to fill up memory with unused objects.
             vt = New Version()
         Next 
     End Sub
 End Class
' The output from the example resembles the following:
'       Memory used before collection:       79,392
'       Memory used after full collection:   52,640

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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