Memory in windows forms

[Marina]

Hi,
Consider the following situation
I have the following routine running repeatedly (curControl is a UserControl
with say 1000 textboxes and a big array of strings):

Public Sub AddControl(ByVa l ctlName As String)
If Not IsNothing(curCo ntrol) Then
Me.Controls.Rem ove(curControl)
End If

Dim assemb As [Assembly] = [Assembly].Load("MyContro lAssembly")
curControl = CType(assemb.Cr eateInstance(ct lName), UserControl)
curControl.Loca tion = New Point(150, 20)
Me.Controls.Add (curControl)
End Sub

Now, running this Sub over and over, the memory stays more or less the same.
That is to say, it goes up a litte bit - maybe 4-20K, but nothing huge.

Now, consider this version:

Public Sub AddControl(ByVa l ctlName As String)
If Not IsNothing(curCo ntrol) Then
curControl.Disp ose()
End If

Dim assemb As [Assembly] = [Assembly].Load("MyContro lAssembly")
curControl = CType(assemb.Cr eateInstance(ct lName), UserControl)
curControl.Loca tion = New Point(150, 20)
End Sub

Now, in this version, the control is not being added to the form - it is
just created.

In this case, the memory goes up by about .5 MB every time this code runs.

Now, the questions is, why is it that in the first scenario, the control is
cleaned up properly - but in the second scenario (where Dispose is actually
being closed), it is not. The memory keeps climbing up and up.

Thanks

In the second example, you're calling dispose, but you're not removing the
control, so a reference to it remains. You should call
Me.Controls.Rem ove(curControl) then curControl.Disp ose() in both case. It's
not an either/or situation.

Pete

"Marina" <so*****@nospam .com> wrote in message
news:uZ******** ******@TK2MSFTN GP09.phx.gbl...

Hi,
Consider the following situation
I have the following routine running repeatedly (curControl is a UserControl with say 1000 textboxes and a big array of strings):

Public Sub AddControl(ByVa l ctlName As String)
If Not IsNothing(curCo ntrol) Then
Me.Controls.Rem ove(curControl)
End If

Dim assemb As [Assembly] = [Assembly].Load("MyContro lAssembly")
curControl = CType(assemb.Cr eateInstance(ct lName), UserControl)
curControl.Loca tion = New Point(150, 20)
Me.Controls.Add (curControl)
End Sub

Now, running this Sub over and over, the memory stays more or less the same. That is to say, it goes up a litte bit - maybe 4-20K, but nothing huge.

Now, consider this version:

Public Sub AddControl(ByVa l ctlName As String)
If Not IsNothing(curCo ntrol) Then
curControl.Disp ose()
End If

Dim assemb As [Assembly] = [Assembly].Load("MyContro lAssembly")
curControl = CType(assemb.Cr eateInstance(ct lName), UserControl)
curControl.Loca tion = New Point(150, 20)
End Sub

Now, in this version, the control is not being added to the form - it is
just created.

In this case, the memory goes up by about .5 MB every time this code runs.

Now, the questions is, why is it that in the first scenario, the control is cleaned up properly - but in the second scenario (where Dispose is actually being closed), it is not. The memory keeps climbing up and up.

Thanks

[Marina]

I apologize for the misprint. That line that adds the control is actually
commented out in my experiment for test #2.

<pd******@hotma il.com> wrote in message
news:15******** *************** *******@news.me ganetnews.com.. .

In the second example, you're calling dispose, but you're not removing the
control, so a reference to it remains. You should call
Me.Controls.Rem ove(curControl) then curControl.Disp ose() in both case. It's not an either/or situation.

Pete

"Marina" <so*****@nospam .com> wrote in message
news:uZ******** ******@TK2MSFTN GP09.phx.gbl...

Hi,
Consider the following situation
I have the following routine running repeatedly (curControl is a

UserControl

with say 1000 textboxes and a big array of strings):

Public Sub AddControl(ByVa l ctlName As String)
If Not IsNothing(curCo ntrol) Then
Me.Controls.Rem ove(curControl)
End If

Dim assemb As [Assembly] = [Assembly].Load("MyContro lAssembly")
curControl = CType(assemb.Cr eateInstance(ct lName), UserControl)
curControl.Loca tion = New Point(150, 20)
Me.Controls.Add (curControl)
End Sub

Now, running this Sub over and over, the memory stays more or less the

same.

That is to say, it goes up a litte bit - maybe 4-20K, but nothing huge.

Now, consider this version:

Public Sub AddControl(ByVa l ctlName As String)
If Not IsNothing(curCo ntrol) Then
curControl.Disp ose()
End If

Dim assemb As [Assembly] = [Assembly].Load("MyContro lAssembly")
curControl = CType(assemb.Cr eateInstance(ct lName), UserControl)
curControl.Loca tion = New Point(150, 20)
End Sub

Now, in this version, the control is not being added to the form - it is
just created.

In this case, the memory goes up by about .5 MB every time this code runs.
Now, the questions is, why is it that in the first scenario, the control

is

cleaned up properly - but in the second scenario (where Dispose is

actually

being closed), it is not. The memory keeps climbing up and up.

Thanks

[Cor Ligthert]

Hi Marina,

You got no further answers I see, my thought was that the dispose is maybe
not well done in your usercontrol. However just a gues and therefore such a
late answer.

In your example 1 you set a reference to the control and remove that
reference
In your example 2 you set no reference to the control so there is nothing to
remove

So example 2 should work the same as example 1 even without the dispose.
That would mean in my opinion that in the dispose a reference is set.

However just guessing.

Cor

[Marina]

In the first example, I do not call Dispose at all. I just add the control
so it is visible - and then remove it.
However, the control is cleaned up properly, and its memory released.

In the second version, I tried doing everything the same exact the
add/remove. The memory was now not released properly.

I then tried adding the Dispose, just in case. This didn't help.

The questions is: why is adding/removing the control to the form, somehow
clean up its memory when the control is no longer referenced by anything.
But just creating it, and dereferencing it, does not?

"Cor Ligthert" <no**********@p lanet.nl> wrote in message
news:ut******** ******@tk2msftn gp13.phx.gbl...

Hi Marina,

You got no further answers I see, my thought was that the dispose is maybe
not well done in your usercontrol. However just a gues and therefore such a late answer.

In your example 1 you set a reference to the control and remove that
reference
In your example 2 you set no reference to the control so there is nothing to remove

So example 2 should work the same as example 1 even without the dispose.
That would mean in my opinion that in the dispose a reference is set.

However just guessing.

Cor

[Cor Ligthert]

Hi Mariane,

I thought that you would have done as you said and that that was your start,
in my opinion is this a typical question for Jon.

It seems as you said that the add and/or the remove are adding/removing
references more than only the reference to the parent.

However why would there be a reference.

I do not like this kind of problems anymore, it is following deep the code
and than reading somewhere else suddenly why this behaviour is.

Cor

[Jon Skeet [C# MVP]]

Cor Ligthert <no**********@p lanet.nl> wrote:

I thought that you would have done as you said and that that was your start,
in my opinion is this a typical question for Jon.

It seems as you said that the add and/or the remove are adding/removing
references more than only the reference to the parent.

However why would there be a reference.

I do not like this kind of problems anymore, it is following deep the code
and than reading somewhere else suddenly why this behaviour is.

Okay, I'll have a look.

Marina, could you come up with a short but complete example which
demonstrates the problem?

See http://www.pobox.com/~skeet/csharp/complete.html

(Don't worry, you don't need to write it in C# - I just want to be able
to paste your code into an empty text file and compile it from the
command line.)

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Marina]

Ok, here is a complete program. First file is the form, second is the
UserControl in question.

Run it and click button1 repeatedly. Memory will keep growing and growing
with every click (500K at a time or so).

Stop it, and run it again. This time click button2 repeatedly. Memory will
grow at first, but remain steady - growing maybe 4-20K at a time - so barely
noticeable.

Thanks for your interest...

Form:

Public Class Form1
Inherits System.Windows. Forms.Form
#Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'This call is required by the Windows Form Designer.
InitializeCompo nent()
'Add any initialization after the InitializeCompo nent() call
End Sub
'Form overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Disp ose()
End If
End If
MyBase.Dispose( disposing)
End Sub
'Required by the Windows Form Designer
Private components As System.Componen tModel.IContain er
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
Friend WithEvents Button1 As System.Windows. Forms.Button
Friend WithEvents Button2 As System.Windows. Forms.Button
<System.Diagnos tics.DebuggerSt epThrough()> Private Sub InitializeCompo nent()
Me.Button1 = New System.Windows. Forms.Button
Me.Button2 = New System.Windows. Forms.Button
Me.SuspendLayou t()
'
'Button1
'
Me.Button1.Loca tion = New System.Drawing. Point(24, 24)
Me.Button1.Name = "Button1"
Me.Button1.TabI ndex = 0
Me.Button1.Text = "Button1"
'
'Button2
'
Me.Button2.Loca tion = New System.Drawing. Point(24, 64)
Me.Button2.Name = "Button2"
Me.Button2.TabI ndex = 1
Me.Button2.Text = "Button2"
'
'Form1
'
Me.AutoScaleBas eSize = New System.Drawing. Size(5, 13)
Me.ClientSize = New System.Drawing. Size(552, 598)
Me.Controls.Add (Me.Button2)
Me.Controls.Add (Me.Button1)
Me.Name = "Form1"
Me.Text = "Form1"
Me.ResumeLayout (False)
End Sub
#End Region
Dim curControl As UserControl
Private Sub Button1_Click(B yVal sender As System.Object, ByVal e As
System.EventArg s) Handles Button1.Click
If Not IsNothing(curCo ntrol) Then
curControl.Disp ose()
End If
curControl = New UserControl1
End Sub
Private Sub Button2_Click(B yVal sender As System.Object, ByVal e As
System.EventArg s) Handles Button2.Click
If Not IsNothing(curCo ntrol) Then
Controls.Remove (curControl)
End If
curControl = New UserControl1
curControl.Loca tion = New Point(50, 50)
Controls.Add(cu rControl)
End Sub
End Class

UserControl:

Public Class UserControl1
Inherits System.Windows. Forms.UserContr ol
#Region " Windows Form Designer generated code "
Public Sub New()
MyBase.New()
'This call is required by the Windows Form Designer.
InitializeCompo nent()
'Add any initialization after the InitializeCompo nent() call
init()
End Sub
'UserControl1 overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
If Not (components Is Nothing) Then
components.Disp ose()
End If
End If
MyBase.Dispose( disposing)
End Sub
'Required by the Windows Form Designer
Private components As System.Componen tModel.IContain er
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<System.Diagnos tics.DebuggerSt epThrough()> Private Sub InitializeCompo nent()
'
'UserControl1
'
Me.Name = "UserContro l1"
Me.Size = New System.Drawing. Size(392, 424)
End Sub
#End Region
Dim myData As New ArrayList
Public Sub init()
For i As Integer = 1 To 1000
Dim t As TextBox = New TextBox
t.Location = New Point(0, i * 40)
t.Text = i & "test"
Me.Controls.Add (t)
myData.Add(i & "test")
Next
End Sub
End Class

"Jon Skeet [C# MVP]" <sk***@pobox.co m> wrote in message
news:MP******** *************** *@msnews.micros oft.com...

Cor Ligthert <no**********@p lanet.nl> wrote:

I thought that you would have done as you said and that that was your start, in my opinion is this a typical question for Jon.

It seems as you said that the add and/or the remove are adding/removing
references more than only the reference to the parent.

However why would there be a reference.

I do not like this kind of problems anymore, it is following deep the code and than reading somewhere else suddenly why this behaviour is.

Okay, I'll have a look.

Marina, could you come up with a short but complete example which
demonstrates the problem?

See http://www.pobox.com/~skeet/csharp/complete.html

(Don't worry, you don't need to write it in C# - I just want to be able
to paste your code into an empty text file and compile it from the
command line.)

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Cor Ligthert]

Hi Marina/Jon,

Can you try this also,

With me it was not the add handler that triggered the cleaning up of the
memory however it seems to me the changing of the form, (or how you want to
say that).

(I added that dispose in button2 proc because otherwise the program went
completly down).

With visible is true the behaviour as described by Marina the same by me,
with visible = false seems the behaviour for Button1 and Button2 the same.
(I used the taskmanager and nothing more).

However maybe I thougth it alone.

Cor
\\\\
Private Sub Button1_Click(B yVal sender As System.Object, _
ByVal e As System.EventArg s) Handles Button1.Click
For i As Integer = 0 To 100
If Not IsNothing(curCo ntrol) Then
curControl.Disp ose()
End If
curControl = New UserControl1
Next
End Sub
Private Sub Button2_Click(B yVal sender As System.Object, _
ByVal e As System.EventArg s) Handles Button2.Click
For i As Integer = 0 To 100
If Not IsNothing(curCo ntrol) Then
Controls.Remove (curControl)
curControl.Disp ose()
End If
curControl = New UserControl1
curControl.Loca tion = New Point(50, 50)
curControl.Visi ble = False 'this to change
Controls.Add(cu rControl)
Next
End Sub
////

[Armin Zingler]

"Marina" <so*****@nospam .com> schrieb

Private Sub Button1_Click(B yVal sender As System.Object, ByVal e
As System.EventArg s) Handles Button1.Click
If Not IsNothing(curCo ntrol) Then
curControl.Disp ose()
End If
curControl = New UserControl1
End Sub Private Sub Button2_Click(B yVal sender As System.Object, ByVal e
As System.EventArg s) Handles Button2.Click
If Not IsNothing(curCo ntrol) Then
Controls.Remove (curControl)
End If
curControl = New UserControl1
curControl.Loca tion = New Point(50, 50)
Controls.Add(cu rControl)
End Sub

Maybe it's too simple, but I think the solution is that clicking Button2
uses much more memory because the control is added to the Form. This causes
the garbage collection and memory to be freed. With Button1, you also need
a lot of memory, but not as much as when making the Usercontrol including
1000 textboxes visible as done in Button2_click, so Button1_click consumes
much less memory and consequently GC isn't started.
Simply leave out curControl.disp ose in Button1_click and you will see that
memory is freed earlier. I also suggest to add this to the Usercontrol:

Protected Overrides Sub Finalize()
Debug.WriteLine ("finalize " & Date.Now.TimeOf Day.ToString)
MyBase.Finalize ()
End Sub

In Sub New:
Debug.WriteLine ("Sub New " & Date.Now.TimeOf Day.ToString)

In Sub Dispose:
Debug.WriteLine ("Dispose " & Date.Now.TimeOf Day.ToString)

Now, without curControl.disp ose in Button1_click, pressing Button1 consumes
memory faster and you will see that GC will take place after few clicks
(after 6 here at my machine). Try this also including curControl.disp ose and
you'll see the difference.
In other words:
When calling dispose, less memory is consumed than when not calling dispose.
Consequently GC takes place later and memory is freed later.
When not calling dispose, memory is consumed faster and GC takes place
earlier. Consequently memory is freed earlier.

I'm not 100% sure but I think this can be the explanation.
--
Armin

How to quote and why:
http://www.plig.net/nnq/nquote.html
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