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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)

'Declaration
Public Shared Function GetGeneration ( _
	wo As WeakReference _
) As Integer

Parameters

wo
Type: System.WeakReference

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

Return Value

Type: System.Int32
The current generation number of the target of wo.

ExceptionCondition
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.

Imports System

Namespace GCGetGenerationWeakExample

   Class MyGCCollectClass
      Private maxGarbage As Long = 1000

      Public Shared Sub Main()
         ' Create a strong reference to an object. 
         Dim myGCCol As 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. 
         Dim wkref As New WeakReference(myGCCol)
         ' Remove the strong reference to myGCCol.
         myGCCol = Nothing 

         ' 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 e As Exception
            Console.WriteLine("The WeakReference to the object " & _
                              "has been garbage collected: '{0}'", e)
            Console.Read()
         End Try 
      End Sub 


      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 i
      End Sub 
   End Class 
End Namespace

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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