.net - Release DC Before Or After Graphics.Dispose?
Jun 1, 2012
On the back of a Windows Form, I get a window DC, create a Graphics object with Graphics.FromHdc, and then dispose the Graphics object before releasing the DC.
Private Declare Function GetWindowDC Lib "user32.dll" (ByVal hwnd As IntPtr) As IntPtr
Private Declare Function ReleaseDC Lib "user32.dll" (ByVal hwnd As IntPtr, ByVal hdc As IntPtr) As Integer
Dim hdc As IntPtr = GetWindowDC(Me.Handle)
[code]....
Why did they do it this way?Should the DC be released before or after Graphics.Dispose?It is possible that the wrong order can cause resource leaks or memory corruption?
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Apr 13, 2010
An application that has 3 Webbrowsers instantiated at design time navigates to webbrowser2 15 times every minute with a different webpage. Webbrowser2 is disposed of after each web page is received and processed. The size of the private application memory continues to grow as when the disposal was not instigated. The application memory grows to 1GB and then the program stops responding. Any suggestions? [Code]
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Jun 14, 2009
I have an app that loads a jpg into a picyure box, then updates exif data in exifworks classThe problem is that when I save the image(from image used for picture box) or class (to save exif data) then try to delete, sometimes I get success, others it won't allow delet I have gone to the trouble of using gc.collect, do events, put the delete in a timer & wait for the delete before continuing & still get the problem
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Oct 23, 2008
Is there a way to have a form within a program that doesn't dispose when you close it? I have a form in my project and a menu item to show it. When I declare the form globally and show in menuItem.click, then the click event breaks because the form no longer exists. When I declare the form within menuItem.click, then this creates a new form every time I click and that's not what I want.
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Jun 25, 2012
I looked at the Dispose() method in System.Data.SqlClient.SqlTransaction (using a decompiler):
[Code]....
Why does everyone say in forums that it is Rolling back in the dispose? Where does it rollback?
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Sep 23, 2011
We have a GIS application that has some performance issues. It creates and sends an image to a web browser. We start with a Bing Maps imager, add complex polygons (complete with transparent fill), save the finished image as a PNG, and send it to the browser.
The idea has come up that we could possibly install a graphics card and use DirectX or OpenGL to improve performance. I believe this would be the case even though we ultimately generate an image instead of sending the data the the screen. I believe our processes could still make use of the API and the hardware acceleration it provides. Our process is not unlike what CGI film makers do to render individuals frames of a film, though we simply render a single image and send it, as opposed to the hundreds of thousands of images needed for a single CGI film.
So my question is: would a powerful graphics card and use of DirectDraw or OpenGL provide us a worthwhile performance boost? It can take us 20-30 seconds to render a more complex map. Which is a long time to wait on a web page...
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Nov 19, 2010
Im working on a project that needs to print a report of one client.Everything went smooth untill i came across my multiline input text data.When i display it in the PrintPagePreview the text go's outside my page. Even when im printing it only the halve of my text is displayed. I googled and looked everywhere but i can't get a clear fix for it.
[Code]...
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Jan 22, 2011
I used to program with Visual Basic 6, so I have alot of old programs that I'm updating, plus I'm learning the new VB2008 methods. I'm writing a program that replaces the old "BitBlit" function which is no longer supported by Visual Basic 2008. It involves three picture boxes, one holds the sprite bitmap, a second holds the mask (silhouette) of the sprite bitmap, and a third has a background image.
[Code]...
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Aug 14, 2009
drawing text on a window which is not the current form's window.I remember doing this in Win32 api with getwindowdc(handle) to obtain a DC for the Window, then textout() on the DC.
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Jan 12, 2011
Ok, I want to create a class that will handle a special rectangle graphic.In my form, I want to have two of these special rectangles. So, basically, I need two instances of that class in my form, right?I manage to initialize two, alright. But, how exactly am I supposed tomanage drawing/graphics etc in a class, and the results to be displayed in my form?
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Oct 29, 2008
Using graphics paths for designing...but am getting an error when trying to add a shape to : _shapelist.add(createshape())
It says : Value of type 'system.drawing.drawing2d.graphicspath' cannot be converted to '1-dimensional array of system.drawing.drawing2d.graphicspath'
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Sep 27, 2010
[code]...
ok, i know the code is a little rough, but it should be good to give you an idea of what im trying to do, if not i will still explain.simply draw 2 lines one from left to right, another from top to bottom, intersecting through the tip of the mouse.ok, theres no problem there the lines draw perfectally the way i want them.... BUT! now heres the issue im having.i cant get rid the previous lines.i did a bit of good old "Google'ing" and ran across a few links that all pointed me to the ReDrawWindow API, so i tried (as you can see in the above code) but i just cant seem to get it worked out.
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Jan 19, 2011
So I decided to make my famous tile selector project, but instead of drawing in a form's graphics, do it inside a tabpage.Well, I managed to get it working, but it seems to... flicker.Normally, setting the form's DoubleBuffered property to True would help a lot there, but apparently, the tabpage has no such property.
When I invalidate the tabpage, I draw two images and fill one rectangle.Following past advice, those two images were created before, just once, and are stored in a variable so I don't create them every time I invalidate the tabpage.
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Aug 1, 2010
Ok I have this: This makes a sub called 'graphicspaint' then writes "demo version" to a picturebox1
Code:
Imports System.Drawing
Imports System.Windows.Forms
[code]......
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Dec 5, 2011
i whant do my own shadow effect. i can do the shandow. but how can i plus 2 bitmap images(1 above the other)?
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Oct 20, 2011
My application is all centered around one form with lots of graphics drawings on it.All these drawings take place from within a paint event handler. However, the amount of code within that sub is becomming unwieldy.I have been trying to move sonme of it to another class and use the "dim temp as Graphics = e.graphics" construction to continue to draw graphics. However, I get all kind of argument exception runtime arreors when doing so (and I do not get these with the same graphics operations directly from the original paint event handler. I have also tried to pass on the original e argument, but with the same result.Is my conclusion that there is no solution to this so to continue with the unwieldy amount of code,correct, or am I mistaken somewhere. the "dim temp as graphics = e graphics" is recommended.
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Oct 28, 2011
I load my picturebox with a jpeg. If I put my DrawObjects() sub into picturebox paint event.When ever a picturebox.refresh or picturebox.visible = true (vb.net seems to draw my DrawObjects() first, then load the jpeg Image over my drawing - erasing drawing) Is there a way to get the picturebox to redraw the jpg image first then draw on it, in picturebox paint event?
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Aug 21, 2008
In a Previous Thread, I asked some questions about how to create graphics. Everything was OK, until I realized that the graphics are really slow. While I was trying to find out what the problem was, I realized that the processor load was about 50% and my graphics card was not used at all. So doesn't Visual Basic use the Graphics Accelerator to process graphics? What I made is not a real program. It's like an experiment (I tried to make an image flip). Here is the Code:
[Code]...
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Sep 27, 2009
Ho to use xxx.DISPOSE() under VB.net
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Oct 13, 2009
I have a program, and there is a timer to run it every 15 minutes. Every time it run, it will create a new exe / thread, (I monitor this thru an external software called TCPView). With the thread growing, it may slow down the performance, is there a way to dispose the thread before a new one is created?
Private Sub Processing()
Dim tmrThreadingTimer As Threading.Timer
Try
[code]....
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May 13, 2011
I am having fun working with System.Threading.Tasks. Many of the code samples I see, however, look something like so:
Dim lcTask = Task.Factory.StartNew(Sub() DoSomeWork())
Dim lcTaskLong = Task.Factory.StartNew(Sub() DoSomeWork(), TaskCreationOptions.LongRunning)
Task.WaitAll(lcTask, lcTaskLong)
That's the extent of the sample.Tasks implement IDisposable, so obviously I'm supposed to dispose of them, but what if I just want to "Fire and Forget"?If I don't dispose, will I leak threads/handles/memory/karma?Am I using tasks "wrong"? (Should just use a delegate and leave tasks alone?)
Can I dispose in a "ContinueWith()"? (That seems like playing Russian Roulette.)[URL]..
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Jan 28, 2009
When is it appropriate to apply the dispose method to controls?For example in a form that has five group boxes, once the first group box is used to gather user entries and is no longer needed, is it worth it to apply the dispose method to the first group box? Is it needed for local variables, for example a StringBuilder used within a private function which is only used while the function is executing?
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Mar 1, 2011
[Code]...
Here I am Clear the object using Dispose( Mycmd.Dispose()). Can I Use here Nothing ( Mycmd = Nothing?. Which is the Best ?
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Sep 21, 2009
I attempting to dispose / close a startup form from a sub. Basically, I using the filesystemwatcher to watch for file creation, if the file is created, run some code and close the form.how to pass in some reference form. Using and new to vs2008. A bit of leap from VB 6.0.
Imports System.IO
Public watchfolder As System.IO.FileSystemWatcher
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
[code]....
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Dec 11, 2010
Hello, I have a WPF Window that I show with Window.Show(). When I click X the form closes. But it is still in memory and the GC never comes and cleans it up. Also I do not have any refrences/handles to it.
I am using the following code with the window:
Code:
Public Class PageWindow
Implements System.IDisposable
Public UserPressedExit As Boolean
[Code]....
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Jan 7, 2010
I was experimenting with ways to get rid of some memory leaks within my application the other day when I realized that I know virtually nothing about cleaning up my resources. I did some research, and hoped that just calling the .dispose() would solve all of my problems. We have a table in our database that contains about 65,000 records. Obviously when I fill my dataset from the dataadapter, the memory usage can get pretty high. When I called the dispose method on the dataset, I was surprised to find out that NONE of the memory got released.
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Jul 22, 2010
Out of pure curiosity, is there a way to free the memory used by a StringBuilder, other than the obvious MyBuilder = New StringBuilder and MyBuilder.Remove(0, Length) (although I guess the later wouldn't free anything, would it?)
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Jan 2, 2012
I create class as Person and include a public sub Insert_DB I write down this code in form
vb
Dim MyPerson As New Person MyPerson.Insert_DB(Me.TextBox1.Text, Me.TextBox2.Text, Me.TextBox3.Text)
I tried to set Dispose to MyPerson (MyPerson.Dispose)but didn't show me Dispose
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Feb 12, 2012
hi everyone i created a thumbnail dll for my file type my class dll create thumb for my files type but my class no dispose after create thumbnail this is my project : HPTShellExtThumbnailHandler.rar
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Apr 7, 2011
I am trying to do a game application similar to chess, where i need to move the game peaces(graphics) over another graphics which is the game board. using the mouse. How can I do multiple layers of graphics and control their movement(without using direct x, i know nothing about it)? Note: I have visual basic 2010 express, windows xp home
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