VB.Net/Development/Garbage Collection
Содержание
Force a garbage collect
Imports System
Imports System.Drawing
Imports System.Data
Imports System.IO
Imports System.Collections
Imports System.Windows.Forms
Imports System.Drawing.Printing
Public Class MainClass
Shared Sub Main()
Dim o As MyObject = New MyObject
o = Nothing
GC.Collect()
End Sub
End Class
Public Class MyObject
" Constructor - called when the object is started...
Public Sub New()
Console.WriteLine("Object " & GetHashCode() & " created.")
End Sub
" Finalize - called when the object is removed from memory...
Protected Overrides Sub Finalize()
MyBase.Finalize()
" tell the user we"ve deleted...
Console.WriteLine("Object " & GetHashCode() & " finalized.")
End Sub
End Class
Force Garbage Collection
Imports System.IO
Module Module1
Sub Main()
Dim c1 As New Contact("Name 1", "111-555-1111", "1@1.ru")
Dim c2 As New Contact("Name 2", "222-555-1212", "2@2.ru")
Dim c3 As New Contact("Name 3", "333-555-1212", "3@3.ru")
c1 = Nothing " Discard the object
GC.Collect()
Console.WriteLine("Back from first collection")
c3 = Nothing " Discard the object
GC.Collect()
Console.WriteLine("Back from second collection -- Press Enter")
End Sub
End Module
Class Contact
Public Name As String
Public Phone As String
Public EMail As String
Sub New(ByVal ContactName As String, ByVal ContactPhone As String, ByVal ContactEmail As String)
Console.WriteLine("Name: " & ContactName & " Phone " & ContactPhone & " Email " & ContactEmail)
Name = ContactName
Phone = ContactPhone
EMail = ContactEmail
End Sub
Protected Overrides Sub Finalize()
Console.WriteLine("In Finalize for " & Name)
End Sub
End Class
Garbage collection started
Imports System
Public Class MainClass
Shared Sub Main(ByVal args As String())
Dim myform As New Form1()
End Sub
End Class
Public Class Form1
Public Running As Boolean
Private Class Junk
Public MyForm As Form1
Public Sub New(ByVal my_form As Form1)
MyForm = my_form
End Sub
" Garbage collection started.
Protected Overrides Sub Finalize()
" Stop making objects.
MyForm.Running = False
End Sub
End Class
Public Sub New()
Running = True
Dim new_obj As Junk
Dim max_i As Long
For i As Long = 1 To 100000
new_obj = New Junk(Me)
If Not Running Then
max_i = i
Exit For
End If
Next i
Console.WriteLine("Allocated " & max_i.ToString & " objects")
End Sub
End Class
GC Suppress Finalize me
Imports System
Imports System.Drawing
Imports System.Data
Imports System.IO
Imports System.Collections
Imports System.Windows.Forms
Imports System.Drawing.Printing
Public Class MainClass
Shared Sub Main()
Dim file As New MyFile("c:\FinalizeDemo.txt")
" now, clear the reference to the object...
file.Dispose()
file = Nothing
" wait for the user to press return...
Console.WriteLine("Press Return to collect the garbage...")
" force a collect...
GC.Collect()
" wait for the user to quit...
Console.WriteLine("Press Return to quit...")
End Sub
End Class
Public Class MyFile
Implements IDisposable
Private stream As FileStream
Private isDisposed As Boolean
Public Sub New(ByVal filename As String)
stream = New FileStream("test.txt", FileMode.OpenOrCreate)
Console.WriteLine("Object " & GetHashCode() & " created.")
Console.WriteLine("Using file: " & filename)
End Sub
Public Sub Dispose() Implements System.IDisposable.Dispose
If isDisposed = True Then Return
stream.Close()
stream = Nothing
isDisposed = True
GC.SuppressFinalize(Me)
Console.WriteLine("Object " & GetHashCode() & " disposed.")
End Sub
Protected Overrides Sub Finalize()
Dispose()
Console.WriteLine("Object " & GetHashCode() & " finalized.")
End Sub
End Class
Get GC generation
Module Module1
Sub Main()
Dim myObject As Object = New Object()
Dim i As Integer
For i = 0 To 3
Console.WriteLine(String.Format("Generation = {0}", _
GC.GetGeneration(myObject)))
GC.Collect()
GC.WaitForPendingFinalizers()
Next i
Console.Read()
End Sub
End Module
Object Generation
Imports System
Imports System.Text
Imports System.Text.RegularExpressions
Public Class MainClass
Shared Sub Main( )
Dim myObject As Object = New Object()
Dim i As Integer
For i = 0 To 3
Console.WriteLine(String.Format("Generation = {0}", _
GC.GetGeneration(myObject)))
GC.Collect()
GC.WaitForPendingFinalizers()
Next i
End Sub "Main
End Class
Request garbage collection
Imports System
Public Class MainClass
Shared Sub Main(ByVal args As String())
Console.WriteLine("Students before instantiation: " & Student.Count)
Dim student1 As Student = New Student("A", "B")
Dim student2 As Student = New Student("C", "D")
" output of student2 after instantiation
Console.WriteLine("Students after instantiation: " & vbCrLf & _
"via Student.Count: " & Student.Count)
" display name of first and second student
Console.WriteLine(vbCrLf & "Students 1: " & _
student1.FirstName & " " & student1.LastName & _
vbCrLf & "Student 2: " & student2.FirstName & " " & _
student2.LastName)
" mark student1 and student2 for garbage collection
student1 = Nothing
student2 = Nothing
System.GC.Collect() " request garbage collection
End Sub
End Class
" Class Student uses Shared variable.
Class Student
Inherits Object
Private mFirstName As String
Private mLastName As String
" number of objects in memory
Private Shared mCount As Integer
" Student constructor
Public Sub New(ByVal firstNameValue As String, _
ByVal lastNameValue As String)
mFirstName = firstNameValue
mLastName = lastNameValue
mCount += 1 " increment shared count of students
Console.WriteLine _
("Student object constructor: " & mFirstName & _
" " & mLastName)
End Sub " New
" finalizer method decrements Shared count of students
Protected Overrides Sub Finalize()
mCount -= 1 " decrement mCount, resulting in one fewer object
Console.WriteLine _
("Student object finalizer: " & mFirstName & _
" " & mLastName & "; count = " & mCount)
End Sub " Finalize
" return first name
Public ReadOnly Property FirstName() As String
Get
Return mFirstName
End Get
End Property " FirstName
" return last name
Public ReadOnly Property LastName() As String
Get
Return mLastName
End Get
End Property " LastName
" property Count
Public Shared ReadOnly Property Count() As Integer
Get
Return mCount
End Get
End Property " Count
End Class " Student