System.NullReferenceException : System.Windows.Forms

TheMSsForum.com: The Microsoft Software Forum

The MSS Forum ‹ Winforms
- Archive
  - Biz
  - MCSE
  - CRM
  - Drivers
  - Framework
  - ADO
  - ASP
  - Compact
  - Forms
  - Dotnet
  - C#
  - VB
  - FontpageGen
  - Excel
  - WorkSheet
  - Exchange
  - Setup
  - Fox
  - Fontpage
  - ASP
  - IIS
  - Entourage
  - Money
  - Messanger
  - PocketPC
  - Powerpoint
  - Project
  - Publisher
  - Excel
  - VB
  - Security
  - Portal
  - Services
  - SQLServerDev
  - SVCS
  - SQLServer
  - VB
  - VC
  - MFC
  - ExcelGen

- Previous
  - 1
    - Ensuring a Form Object is set to Nothing Say I create a form as a child in the following fashion dim Mainfrm as frmMachine ' Globa public sub CreateForm( Mainfrm = New frmMachin Mainfrm.MdiParent = M Mainfrm.Show( end su Now when I close the form (clicking the x), the form gets closed but Mainfrm is still referencing the form address How do I ensure that Mainfrm gets set to Null, so that I can test for the forms existence? Is Mainfrm a type of hanging pointer What happens when, after the form has been closed and CreateForm() is called again? Does the original object get freed or overwritten? Will I have a memory leak? Is the memory freed as I read that memory is only freed when no objects are referencing that memory Am I approaching this incorrectly thanks in advanc Dyla Tag: System.NullReferenceException : System.Windows.Forms Tag: 72687
  - 2
    - Catching events in separate thread? Hi all, I have a windows form that uses an imported COM class to talk to a legacy system. The COM object works asynchronously - An even is fired when data has been returned. This works fine, except that Im getting too many events fired! Thus my windows form becomes pretty sluggish and unresponsive, and CPU utilistaion is pretty high. Is there any way I can set up another thread to recieve and handle these events instead? Do threads have event loops? If so, how do I "direct" events to them? Am I tackling this in the wrong way? Thanks! Spammy Tag: System.NullReferenceException : System.Windows.Forms Tag: 72686
  - 3
    - axWebBrowser View Mode I was unable to get any information on this in microsoft.public.dotnet.framework.windowsforms.controls and I wonder if anybody in this group can give me any pointers? When using the axWebBrowser to look at a folder/directory is it possible to set the view to 'Details' programmatically rather than having to keep using the context menu? -- Jeff Gaines - Damerham Hampshire UK Tag: System.NullReferenceException : System.Windows.Forms Tag: 72685
  - 4
    - Richtextbox clipregion I want to draw a rule on left hand side of a richtextbox, it would have line numbers and should scroll whenever richtextbox scrolls To do that; i've two options 1. Place ruler and richtextbox on an panel; but the problem is that how can i synronize sroll operation! 2. Extend richtextbox and draw a ruler; but how can i tell base class not to draw over my ruler! Does anyone have an idea either one of them! I would be great to see a c# code :) Tag: System.NullReferenceException : System.Windows.Forms Tag: 72681
  - 5
    - ThreadPooling in Grid Control Dear All, We have a Grid Control that fires a WebService in a thread to make UI responsive while the Grid Control is fetching the data...we had used ThreadPool.QueueUserWorkItem for this...this works fine if there is a single Grid object in a Form...if there are more than 3 Grid objects in the same form then we start getting http 404 errors... I would like to execute the population of the Grid one after the other...I guess this is not possible using ThreadPool.QueueUserWorkItem... Is using ThreadPool.RegisterWaitForSingleObject and Mutex the right approach for this? Any ideas? Please help... TALIA Many Regards Jack Tag: System.NullReferenceException : System.Windows.Forms Tag: 72678
  - 6
    - user control host form gets disabled My main form contains a panel which I use to host user controls After I have added and then removed all instances of my user controls from the panel, then move focus away from and back to my app, my main form appears disabled Is there something I need to be doing in my user control? If I use a standard control e.g. Button I don't get the problem A simplified version of my code is shown below using System using System.Windows.Forms namespace WindowsApplication public class MyControl: UserContro public MyControl( this.Controls.Add(new Button()) public class Form1 : For private Panel PanelMain private MyControl t1 public Form1( MenuItem menuAdd = new MenuItem("&Add",new System.EventHandler(this.Add_Click)) MenuItem menuRemove = new MenuItem("&Remove",new System.EventHandler(this.Remove_Click)) this.Menu = new MainMenu(new MenuItem[]{menuAdd,menuRemove}) PanelMain = new Panel() t1 = new MyControl() this.Controls.Add(PanelMain) [STAThread static void Main() Application.Run(new Form1()) private void Add_Click(object sender, System.EventArgs e this.PanelMain.Controls.Add(t1) t1.Focus() private void Remove_Click(object sender, System.EventArgs e this.PanelMain.Controls.Remove(t1); Tag: System.NullReferenceException : System.Windows.Forms Tag: 72676
  - 7
    - Controlbox MDI form Hi, I'm french and I don't find the answer at my question. You are my last chance and sorry for my english... I'm in VB .NET 2002 I have a MDI form with the property ControlBox at FALSE. When the MDI Form appears, no problem, we have not ther controlbox. But when I maximize the MDI Form, the controlBox appears and I DON'T WANT THAT !!!!! How Can I do for that this controlbox don't appears in this MDI form Thanks Sylo Tag: System.NullReferenceException : System.Windows.Forms Tag: 72675
  - 8
    - No Touch and single instance applications not compatible? H I would like to build a single instance application. This means tha if the app is launched a second time it will simply pass any comman line arguements to the instance that is already running and won' start another instance (se http://www.codeproject.com/vb/net/sing_inistan.asp) This all works fine locally but fails under "No Touch" deployment. Th error is "Cannot find the assembly SingleInstance Version=1.0.1615.28371, Culture=neutral, PublicKeyToken=null" If you have any suggestions please send them to mark.evans@DELETETHISstats.govt.n Cheer Mar Tag: System.NullReferenceException : System.Windows.Forms Tag: 72669
  - 9
    - No Touch and single instance applications not compatible? Hi I would like to build a single instance application. This means that if the app is launched a second time it will simply pass any command line arguements to the instance that is already running and won't start another instance (see http://www.codeproject.com/vb/net/sing_inistan.asp). This all works fine locally but fails under "No Touch" deployment. The error is "Cannot find the assembly SingleInstance, Version=1.0.1615.28371, Culture=neutral, PublicKeyToken=null". Please email any advice to mark.evans@stats.govt.nz Cheers Mark Tag: System.NullReferenceException : System.Windows.Forms Tag: 72667
  - 10
    - Checking for instantiated form How do I check to see if a form is already instantiated in an MDI app? Tag: System.NullReferenceException : System.Windows.Forms Tag: 72666
  - 11
    - TreeView flashing when resizing a form I've seen several posts from people who have seen this flashing in TreeView's when resizing a form. I've noticed it in my app, but only in the child windows. For example, my main form has a splitter with a TreeView and I do not get the flickering with it. I created a new Form based Windows app. Added a TreeView (dock left), then a splitter and a property grid on the right (dock fill). For this test, I added a panel and button at the bottom so I could create the child form. I created a second form and created it the exact same way - TreeView on the left, splitter and a property grid on the right. In the click handler for the button on the first form, I create a new "Form2" and call "ShowDialog" passing "this" in as a parameter to make the main form the parent for the dialog. After adding some nodes to each of the tree views, fire up the app. If you resize the main form, you won't see flickering in the tree view. Click the button to show the parent form and resize it - you will see horrible flickering. Now, why is that? With the exception of the extra panel to hold the button on the main form, they are identical, yet the child displayed with ShowDialog shows terrible flickering. If I had to guess (which I guess I am guessing right now :-) I'd say Microsoft was expecting that forms shown with "ShowDialog" would not be made resizable so they left out paint optimizations when resizing. If that is the case, how do we get rid of the flickering when resizing a dialog? Thanks, Terry Tag: System.NullReferenceException : System.Windows.Forms Tag: 72665
  - 12
    - ListView Control I am wondering if it is possible to easily duplicate the ListView control behavior in the Windows explorer when a new folder is defined. I am talking about the scenario where the user wants to create a new folder, the control displays a folder called New Folder which is highlighted inside a rectangle so that the user can easily change the name of New Folder. That is a really slick interface but I know that Microsoft is famous for having slick interfaces that are very difficult for most developers to implement. I am wondering if the rectangle is a special owner-drawn customized implementation. Please advise. Thanks for your help. Best Regards, Paul J. Lay Tag: System.NullReferenceException : System.Windows.Forms Tag: 72658
  - 13
    - activating windows from a separate thread Hi: I'm running a chat application that when called by a remote caller, opens a chat window. Currently, I'm using Application.Run() to create each new window, because I am having problems accessing the window from the non-gui thread. However, I imagine this is very resource intensive, and would rather find a cleaner approach, if possible. In testing possible scenarios, I've noted that a form instantiated inside the constructor of the main window can be called (invoked, actually) from a different thread....if it has already been shown before. By that, I mean if a call to show has been placed on the child form from the parent's gui thread, then subsequent calls work out fine. In debugging, I noted that if the form hasn't already been shown, then the first InvokeRequired call to the form comes back as false. Obviously, this isn't true, since I do need to view the form from the thread that instantiated it. I've tried tricks to get around this with no avail. I've set a flag up so that the first time Load is called from the child form, it's visible flag is set to false. I've done the same with calling hide the first time; i've combined the two. I've called Close on them (which has cancel set to true and hide set). Then I've called them first from the parent's constructor with Show(). They child window doesn't hide. I've tried calling invoke directly without testing...I get an exception because the window hasn't been created yet. I'm running out of options. The only other option I can think of right now is to setup an invisible button and invoke it, which will show the window. I think....that would work...I don't know, though. I've always had problems for some reason with the button.PerformClick() method. Does anyone have any suggestions on ways to get the gui to do its loadup stuff without displaying the child window, so I can call the child window from another thread safely? Any help given is greatly appreciated. Steve Tag: System.NullReferenceException : System.Windows.Forms Tag: 72657
  - 14
    - How do I add a column of buttons to a bound DataGrid control? I have been trying to do this for hours with only limited success. I have no idea why MS makes something that should be so straight forward a real pain. Can anyone point me in the right direction? Tag: System.NullReferenceException : System.Windows.Forms Tag: 72650
  - 15
    - Changing alignment of column in datagrid I thought I had done this before, but I'm apparently overlooking something. All I want to do is set the alignment of the first column to the right. The dataset gives me 5 columns and will auto-format the grid, but I really want to align just one column. Thus the code below. However, the app blows right past my attempt to impose a new table style and auto-formats the grid with everything aligned to the left (I have deleted all table styles from the Datagrid properties, so there is no "default"). Is it possible to set alignment for one column or do ALL need to be manually aligned? Anything else I'm overlooking? DataGrid1.TableStyles.Clear() Dim tblStyle As New DataGridTableStyle tblStyle.MappingName = "History" Dim dgColumn1 As New DataGridTextBoxColumn Dim dgColStyleRight As DataGridColumnStyle dgColumn1 = New DataGridTextBoxColumn dgColumn1.Alignment = System.Windows.Forms.HorizontalAlignment.Center tblStyle.GridColumnStyles.Add(dgColumn1) DataGrid1.CaptionText = "History" DataGrid1.ReadOnly = True DataGrid1.TableStyles.Add(tblStyle) Tag: System.NullReferenceException : System.Windows.Forms Tag: 72642
  - 16
    - Setting a margin in a label Is there a way to set the margins in a label. Specifically, what I need to do is make sure that the text begins 6 pixels to the left of the label border and that the baseline of the text is 5 pixels above the lower border of the label. Is there any way to accomplish this with the standard label or am I going to have to create my own label control? Thanks. Pete Davis Tag: System.NullReferenceException : System.Windows.Forms Tag: 72640
  - 17
    - Using TextBox as a buffer Is there a simple way to use a textbox as a buffer that holds the last N lines or characters for logging info? Thanks. -- Bud Tag: System.NullReferenceException : System.Windows.Forms Tag: 72639
  - 18
    - Turn off inheritance of properties (e.g. Font weight) Hello NG, i have a form (c#) with a tab control. If I change the weight of the font in the tab control all other fonts in the form (e.g. labels) also become this weight. It is a inheritence. How can i turn off this? Thanks, Roland Tag: System.NullReferenceException : System.Windows.Forms Tag: 72638
  - 19
    - Shortcut/accelerator keys Hello all I have two forms open in my app, and they share a same shortcutkey for a drop down box. The same forms in framework 1.0 when the alt+shortcut key is pressed, the drop down box on the form that has focus would be activated. This is expected and desired behaviour. We converted the forms to new framework 1.1. Here when I press alt+shortcut key the focus toggles between the two forms even though only one form has focus. I am not sure if this is a bug with winforms. Tag: System.NullReferenceException : System.Windows.Forms Tag: 72636
  - 20
    - .NET Form and Message Loop Hi, I am using C# code to create a window, get its HWND and pass it to an unmanaged C++ DLL. This DLL has the code to process messages. My problem is that I don't receive the WM_QUIT event so, my application never quits. If I replace the WNDPROC with mine using a call to SetWindowLongPtr, and just check for messages before passing them to the original WNDPROC, I don't even get a WM_DESTROY message. Any idea why this is happening? Any idea how to fix this? Eric Robert Tag: System.NullReferenceException : System.Windows.Forms Tag: 72635
  - 21
    - 3-tiers of vb.net Dear all, i have a question about 3-tiers of vb.net, the presentation tiers is form the database tiers is databas and how about the business tier if i write some dot net component , is it a business tie or if i write some com+ is it a business tie or web service is ?? Tag: System.NullReferenceException : System.Windows.Forms Tag: 72634
  - 22
    - Problem debugging ActiveX component in Windows Form I've added an ActiveX component to a Windows Form and this seems to be working fine. However, I now need to debug the ActiveX component, but can't step into the component - I can step in the Windows Form code, but can't go into any of the code referenced by the ActiveX component, even though this has all been built with a debug solution configuration. Does anyone know how I can get debugging to work in the ActiveX component ? Thanks for any help, Steve Tag: System.NullReferenceException : System.Windows.Forms Tag: 72630
  - 23
    - MDI Mouse Move & KeyPress Events Hi guys, This might be an already answered question, but I was wondering if there is a way to catch the Mouse Move and the KeyPress events if a have a MDI window because it doesn't fire these events (for instance, if I don't have any child form... just the main container). On the other hand, if there is a way to know if an application gets out of an idle state. I know how to control the Application.Idle method and attach it with a handler to method that should be triggered before having an idle state, but I don't see how to manage it if the application is receiving interaction from the user again and I want to reset a timer (for example). Any help or ideas would be appreciated. Thanks, Gustavo Ortega Software Engineer University of CR Tag: System.NullReferenceException : System.Windows.Forms Tag: 72627
  - 24
    - ListView taking a long time to select. I have a ListView that I am showing in 'Detail' mode. The list contains about 740 items and I have a button that tries to go through all items in the list and select them and change the image icon. This seems to take over a minute or two just to do something like foreach(ListViewItem item in listView.Items item.Selected = true item.ImageIndex = 1 Does anyone have any suggestions on how to speed this up? I would hate to guess how long it would take if I had 7000 items in the list. What is taking so long? I have tried to suspend the layout as is done during the Windows initialization but this did not seem to have any effect Thank you for your suggestions Kevin Tag: System.NullReferenceException : System.Windows.Forms Tag: 72625
  - 25
    - How to host a .NET MDI Child Window inside a VB6 MDI Application Hi folks, a bit of a tricky problem to solve for you. I have a scenario where I have a legacy VB6 MDI application that I want to act as a host for a MDI child form that resides in a .NET assembly. I can do the simple stuff such as exposing the .NET Form as a COM object and registering the assembly for COM Interop, the issue is how can I force the .NET Form to become a MDI child of the parent VB6 MDI Parent Window. Any suggestions would be most welcome Tag: System.NullReferenceException : System.Windows.Forms Tag: 72623
- Next
  - 1
    - Focus question I have a form with many controls and I want the focus to stay on a particular textbox no matter what the user does. I don't want to have to code an event for absolutely everything the user can do. I tried the leave event, but the problem with that is if the next event puts text in the textbox then the cursor is at the beginning of the text not the end. I know ways to accomplish this, however I just trying to see if there is a better way. Maybe there is an event that is executed after everything else. Thanks in advance, Will Tag: System.NullReferenceException : System.Windows.Forms Tag: 72620
  - 2
    - Update Problem with Combobox DataGrid I have downloaded DataBound combo box sampl I have got combobox data grid sample from http://www.syncfusion.com/FAQ/WinForms/FAQ_c44c.asp#q480q I added code to update changed records but it does not work.Have some one idea how add update ,new and delete functionality to data grid with combobox coloum.Data grid displays data from two tables,related by foreign key relation.that is typical case often encountered in database applications I have downloaded DataBound combo box sample.My code is based on this sample.Btw can yo tell me about the same problem with other samples.however my primary concern is about databound combo box sampl Tag: System.NullReferenceException : System.Windows.Forms Tag: 72615
  - 3
    - linking to an external file from a application i am using webbrowser control and i want it to display a file when a form loads the file is included in the project but how do i link it AxWebBrowser1.Navigate(" ??? " p.s. - i am a beginner also can i open this newsgroups in outlook express ? Tag: System.NullReferenceException : System.Windows.Forms Tag: 72610
  - 4
    - .Net Windows Application Assembly Downloading Question I have a question on the .Net Windows Application Assembly Downloading Problem I have a windows application with some dlls dependencies. And I have put it into a Web Site with a link to let user to click on the link for the application downloading from the web server automatically. All the exe & dlls are strong name signed already I found that sometimes, some computer cant download some dependencies, which causing the application cant run Do anyone know the reason on that Thanks for the help~~ Tag: System.NullReferenceException : System.Windows.Forms Tag: 72606
  - 5
    - Image within Splitter - Bubbling Click Event I've got a WinForms question, that hopefully isn't too twisty! I'm working with a [Splitter] object, and what I'm wanting to do is maintina good control over it's visual appearance. I'm settings it's BackgroundImage, but what I also want to do is insert an Image within it (which is a visual representation of something to grab - like the grabber image at the bottom-right of a form). For scaling and positional reasons I can't have the grabber icon as part of the actual BG image. Here's the problem: I can insert the image into the [Splitter], and position it just fine. But when the user clicks on it, the [Splitter] won't move, because it is the image recieving the click action, not the containing [Splitter]. Is there some way I can bubble the click event up to the containing [Splitter], so that it thinks it has been clicked, rather that it's child Image control? Thanks everyone. === Phil (Auckland | Aotearoa) Tag: System.NullReferenceException : System.Windows.Forms Tag: 72601
  - 6
    - Help with FlatStyle.System and font Hi, I've tried to search the answer but can't find it so far: Can someone shed some light on how the font was used when button's flat style is FlatStyle.System?? I've tried all sorts of ways, but the button's font always got changed when its container's font was set. Is there a way to set it back to Windows' default? Thanks!! Alan Tag: System.NullReferenceException : System.Windows.Forms Tag: 72600
  - 7
    - OnResize Before Constructor Makes Babies Cry I noticed that my application was throwing an exception in OnResize because an overridden version of OnResize in a class derived from Panel is called before the instance's constructor completes. In fact, OnResize is called before the constructor even starts (!). Sure enough, the MSDN documentation for .NET 1.1 says that this can happen. This means that every class that overrides OnResize has to manually make sure that the instance information used in OnResize is initialized before OnResize uses it. This is quite ridiculous and seems like a bug in the Framework -- imagine if every instance method had to check if its constructor had completed. Why does OnResize behave this way? Are there any other methods that behave like this? Is this going to be fixed? Andrew Tag: System.NullReferenceException : System.Windows.Forms Tag: 72599
  - 8
    - Tab order problem Hi all; I m facing problem in setting tab order . I have to group boxes GB1 and GB2. GB1 has two text boxes T1 and T3. GB2 has two text boxes T2 and T4. I want that tab movement should be T1, T2, T3 and T4 repectively... how can i do that.. Even though I have set the tab index in that order but not getting proper result.... Any suggestion? Thanks in advance.. Ansari Tag: System.NullReferenceException : System.Windows.Forms Tag: 72593
  - 9
    - EventsTab issue with PropertyGrid at runtime I program a simple forms editor like the VS.NET one and got the most of the stuff working. One problem is still unsolved and I need a bit help. The components I want to edit request the EventsTab for the PropertyGrid: [PropertyTab(typeof(System.Windows.Forms.Design.EventsTab), PropertyTabScope.Component)] public class MyControl : UserControl { /// } In the main form I add the type and assign the Site of the current component: this.propertyGrid.PropertyTabs.AddTabType(typeof(System.Windows.Forms.Design.EventsTab)); this.propertyGrid.Site = component.Site; I have also implemented IEventBindingService to handle the code generation: serviceContainer.AddService(typeof(IEventBindingService), new EventBindingService(this)); If I start my form the PropertyGrid shows the EventsTab with the lightning bolt and the BindingService works as expected. If I add another control with the same PropertyTab Attribute on it, the EventsTab disappear and whatever I do it will never come back. The type of control doesn't matter, the first shows the tab and the second removes it. Alongside with the EventsTab appears the standard properties Tab, to let the user switch back to properties view. This automagically added Tab does not disappear and become selected and the standard properties are shown, after the EventsTab button disappers - very strange behavior. Does anybody has a clue what happens here? Do I miss any other interfaces I should implement especially for events handling in my micro-IDE? What exactly do the Site property of the PropertyGrid? I've tried some other ISite implementations, but nothing worked. Do I need to change the property during runtime? Thank you for any idea or pointer to articles. -Joerg Tag: System.NullReferenceException : System.Windows.Forms Tag: 72590
  - 10
    - Windows Forms in web pages with Apache general question Hi! I am wandering if it is possible to host a C# winform in IE 6+ using Apache for the server In the lousy Professional Windows Forms by Wrox, there is a lousy chapter on doing so with IIS. Why can't it be done with Apache ? What does IIS do to support this functionality ? Any help is greatly appreciated Thank you in advance --Sam Tag: System.NullReferenceException : System.Windows.Forms Tag: 72587
  - 11
    - Capturing another window I've got an application (WinForms) with an MDI parent form and several MDI child forms, which all run maximized in the parent. This program needs to integrate in with another program that we have no control over. What I'd like to be able to do is capture another window (one from this other app) and have it appear as an MDI child window in the C# application I've written. First, is this even possible? Maybe not exactly this, but something that would at least achieve a similar appearance? Second, does anyone know how I can go about doing this? Thanks a lot. Ryan Gregg Tag: System.NullReferenceException : System.Windows.Forms Tag: 72580
  - 12
    - string length limit in args sent by ISynchronizeInvoke? I'm raising an event in a component, using ISynchronizeInvoke.Invoke, and my event args object contains a string as one of its members. If the string is longer than 63 bytes, the Invoke call pulls an unhandled exception in System.Windows.Forms.dll, to the effect that the string length must be less than 64. If I trim the string to 31 characters (62 bytes) everything's fine and the event goes as intended. But if the string length is 32 or greater, the unhandled exception gets thrown. Is there some kind of limit in the marshaling that's going on with Invoke? Or what? I've looked on groups.google.com but haven't yet stumbled on search terms that produce any discussion of this. Any ideas? Thanks, Tom Dacon Dacon Software Consulting Tag: System.NullReferenceException : System.Windows.Forms Tag: 72579
  - 13
    - Memory in windows forms 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(ByVal ctlName As String) If Not IsNothing(curControl) Then Me.Controls.Remove(curControl) End If Dim assemb As [Assembly] = [Assembly].Load("MyControlAssembly") curControl = CType(assemb.CreateInstance(ctlName), UserControl) curControl.Location = 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(ByVal ctlName As String) If Not IsNothing(curControl) Then curControl.Dispose() End If Dim assemb As [Assembly] = [Assembly].Load("MyControlAssembly") curControl = CType(assemb.CreateInstance(ctlName), UserControl) curControl.Location = 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 Tag: System.NullReferenceException : System.Windows.Forms Tag: 72578
  - 14
    - "Frames" in windows forms Hi, Just wondering if there is any sort of concept of "frames", as in HTML in windows forms, where different forms can be loaded into different frames. So one of the frames might be loaded with different forms at different times. Or are user controls what one would use to accomplish this sort of thing. Thanks. Tag: System.NullReferenceException : System.Windows.Forms Tag: 72572
  - 15
    - How to create a form looks like the Outlook Form Hi ng, how can i create a form that looks like the DesktopNotification Form from (Office) Outlook 2003. The Form fades in when you receive a new email. I tried to build this form, but it doesn't work. Has someone an idea or an example? thx, Patrick Tag: System.NullReferenceException : System.Windows.Forms Tag: 72566
  - 16
    - System.NullReferenceException in unknown module during startup Hello, I am currently developing some control library for windows forms application in c#. But for some of the test application it throws up error box saying "System.NullReferenceException" in the unknown module as occured. Upon debugging I found that the error is thrown from the garbage collector thread. I could figure out the name of the dll and the method name which is throwing the exception. It occurs in mscorwks.dll!CallFinalizer() method. I do not have clue how this exception is getting generated. When the exception occurs the various constructors of the controls and their embeded constructor is getting called. It occurs before main form load event. The other observation is also that the exception started while we introduced resx file for the various resources in the control library. Any pointer? Thanks Kachra Tag: System.NullReferenceException : System.Windows.Forms Tag: 72553
  - 17
    - form dimensions I have just started trying out vb.net coming from vb6 which i know extremely well My problem is very strange, is it just me or is the top property returning werid values ie. -4. it should be in theory 0 relative to the internal client rect of course that could be the screen position but i can't actually find the equivilent properties from vb6 forms for the internal client rectangle ie. scalewidth etc It just seems like a completely different language, although it does seem more like c++ which i like my only grevience is that it's like learning from scratch again which is quite annoying when you spend all that time learning the details of the core vb stuff then they just change it all in a drop of a hat grr... Tag: System.NullReferenceException : System.Windows.Forms Tag: 72549
  - 18
    - Interpret empty datagrid cells as empty strings When I clear a cell in a datagrid, the corresponding (string) field in the underlying datatable becomes null. I would prefer that it be an empty string, as the corresponding database field is not nullable. Does anyone have any tips as to how to accomplish this? Thomas Berg Tag: System.NullReferenceException : System.Windows.Forms Tag: 72538
  - 19
    - Change a disable control color Hi Does anyone know how to set a color to a disable control (I.E. a textbox when you set the disable property to true you get the gray windows disable color, and I would like to set it in blue I already tried to override the event - OnEnableChange - but it doesn't wor Any tips or trick? Tag: System.NullReferenceException : System.Windows.Forms Tag: 72537
  - 20
    - "MDAC required" but it's installed... Hi, I'm having this error in a VB.NET-application at the moment that I attempt to read data from an SQL Server: The .Net Data SQL Provider (System.Data.SqlClient) requires Microsoft Data Access Components(MDAC) version 2.6 or later. at System.Data.SqlClient.ConnectionPool.GetConnection(Boolean& isInTransaction) at System.Data.SqlClient.SqlConnectionPoolManager.GetPooledConnection(SqlConnec tionString options, Boolean& isInTransaction) at System.Data.SqlClient.SqlConnection.Open() Failed to Load Call Data Call Data Failure However the MDAC 2.7 is installed! And when I look into the registry it is indicated as installed too: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DataAccess\FullInstallVer = "2.71.9040.2" The .NET Framework is installed (1.1), and it is on a Windows NT (Sp 6a) pc. Does anybody know about thisp roblem? And some solution? Could it be because of some restictions (although I do have full Admin rights on the pc). I'ts really urgent and bothering me (I have to do a demo in 20 minutes, hehe). Thanks a lot in advance, any help, hints etc will be really appreciated! Pieter Tag: System.NullReferenceException : System.Windows.Forms Tag: 72536
  - 21
    - Close & restart an application Hi, I would like close & restart the same application automatically. How can I achieve this. Please suggest Thanks & Regards CV Tag: System.NullReferenceException : System.Windows.Forms Tag: 72535
  - 22
    - Control.CreateControl does not create Handle According to the .NET doc, calling the CreateControl() will create a handle for the winform control and its child. But I doesn't seem to get it work. I have a code like this : private void button6_Click(object sender, System.EventArgs e) { m_Form2 = new Form2(); m_Form2.CreateControl(); // This should show me TRUE. But instead, it show me FALSE which is // the not expected. MessageBox.Show(m_Form2.IsHandleCreated.ToString()); } Is this a know issue or I miss out something ? Tag: System.NullReferenceException : System.Windows.Forms Tag: 72532
  - 23
    - DataSource property to control design time I want to add a DataSource property to my control that, at design time, will allow the designer to drop down a list of valid datasource components just like the DataGrid control. The type on the DataSource property is just 'object', so I know it isn't that. Is there a special designer attribute I have to use on my property Actually my Control has a Combobox and i just want to enable the combobox's (DataSource, DisplayMember, ValueMember) properties If I map the properties 1to1 like this [Category("Data"), DefaultValue(null), Description("The datasource that is used to populate the list with items.") public object DataSourc get{return this.comboBox.DataSource; set{this.comboBox.DataSource = value; [DefaultValue(""), Description("Gets or sets the column for display."), Category("Data") public string DisplayMembe get{return this.comboBox.DisplayMember; set{this.comboBox.DisplayMember = value; [DefaultValue(""), Description("Gets or sets the column for value."), Category("Data") public string ValueMembe get{return this.comboBox.ValueMember; set{this.comboBox.ValueMember = value; It breakes the Designers ability to show a dropdown list of avaiable DataSource's. Tag: System.NullReferenceException : System.Windows.Forms Tag: 72527
  - 24
    - How can I get the name of a ToolBarButton object. I need to iterate the Buttons collection in a toolbar and get the name of each button. The objects in the collection are not normal Button objects. They are ToolBarButton objects, which do not appear to have a Name property. Is there some other place to get the name? Tag: System.NullReferenceException : System.Windows.Forms Tag: 72524
  - 25
    - Visual inheritance bug? Hello gurus! In my C# project I have a localized form that I use as the prototype for two others. The prototype form has a ListBox control data bound to an ArrayList containing data elements of a custom class type. At design time its Items collection is empty and is populated by data binding only when the application is executed and the underlying ArrayList collection is created. The inherited forms' ListBox controls seem to somehow mysteriously inherit not only the properties of the prototype form's ListBox control, but also its Items collection. It sounds crazy, but I get errors at compile time which are caused by the code Windows Forms Designer automatically inserts into the InitializeComponent() method. This is what it looks like: this.lstItems.Items.AddRange(new object[] { ((object)(resources.GetObject("lstItems.Items"))), ((object)(resources.GetObject("lstItems.Items1"))), ((object)(resources.GetObject("lstItems.Items2"))), ((object)(resources.GetObject("lstItems.Items3")))}); This line is inserted automatically every time I save the inherited form. It seems that VS caches the number of elements in the Items collection the last time the application is run in debug mode and assumes the elements exist in the resource file, which they don't. Any ideas how to get rid of this annoying behaviour? P.S. If you reply directly, please remove the anti-spamming proclamation from my e-mail address. Tag: System.NullReferenceException : System.Windows.Forms Tag: 72520

Hi,

I've been trying to trace this exception but I can't seem to find the source
of the problem:

Message: "Object reference not set to an instance of an object."

StackTrace: at
System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)\r\n at
System.Windows.Forms.ComponentManager.System.Windows.Forms.UnsafeNativeMetho
ds+IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason,
Int32 pvLoopData)\r\n at
System.Windows.Forms.ThreadContext.RunMessageLoopInner(Int32 reason,
ApplicationContext context)\r\n at
System.Windows.Forms.ThreadContext.RunMessageLoop(Int32 reason,
ApplicationContext context)\r\n at System.Windows.Forms.Application.Run(Form
mainForm)\r\n

Thanks,

RF

Top

Re: System.NullReferenceException : System.Windows.Forms by pdavis68

pdavis68
Thu Jun 03 09:52:32 CDT 2004

Please post the code where this is happening and point out the exact line.
You should be able to find the exact line by stepping through the code. You
may need to add some Debug.WriteLine() statements to help you find the
method/event/property where this is happening.

Pete

"RF" <randy.foz@SPAMdialexia.com> wrote in message
news:uZMgwWXSEHA.1764@TK2MSFTNGP10.phx.gbl...
> Hi,
>
> I've been trying to trace this exception but I can't seem to find the
source
> of the problem:
>
> Message: "Object reference not set to an instance of an object."
>
> StackTrace: at
> System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)\r\n at
>
System.Windows.Forms.ComponentManager.System.Windows.Forms.UnsafeNativeMetho
> ds+IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32
reason,
> Int32 pvLoopData)\r\n at
> System.Windows.Forms.ThreadContext.RunMessageLoopInner(Int32 reason,
> ApplicationContext context)\r\n at
> System.Windows.Forms.ThreadContext.RunMessageLoop(Int32 reason,
> ApplicationContext context)\r\n at
System.Windows.Forms.Application.Run(Form
> mainForm)\r\n
>
>
> Thanks,
>
> RF
>
>

Top