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Hello!
I'm creating a simple VB.NET data application. I have a MDIparent form which will open up my child forms. I have no problem opening up my child forms with a menu bar.
Although for looks, I have added a toolbar to the MDI parent window, so a user can select the form of choice by cliking on a picture (like a pushbutton). I have a toolbar set with 4 icons, for my 4 different forms. I have an imagelist made to complement the buttons so they look nice and pretty.
Now for the problem...When I add code for the toolbar to signify which button is pressed (I wrote case statements), I can only open up one form. If I open up another form after closing the first one, or try to open up 2 forms at one time, I get the following error when in Debug mode:
"An unhandled exception of type 'System.Data.NoNullAllowedException' occurred in system.windows.forms.dll
Additional information: Column 'ID_uniqe' does not allow nulls."
The debug will highlight in Green my show() statement of the form I try to open. Here is my code for signigiy which button is pressed on the toolbar:
Private Sub ToolBar1_ButtonClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ToolBarButtonClickEventArgs) Handles ToolBar1.ButtonClick
Dim m As New DataForm_Main
Dim p As New DataForm_PrHist
Select Case ToolBar1.Buttons.IndexOf(e.Button)
Case Is = 0
m.MdiParent = Me
m.Show()
Case Is = 1
p.MdiParent = Me
p.Show()
End Select
End Sub
AS A NOTE: This coding works fine if I decide to not have child windows. If I completely remove the "m.MdiParent = Me" statements, then the forms open up nicely with no errors - Errors seem to only produce when I have them set for MDI's.
Should I even be using case statement? How can I show the forms in MDI child windows within my parent form?
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First, you might want to move the Dim statements into the Case Is blocks. Its a better idea to allocate the new forms as you need them, not before you determine that. This will save the garbage collector some time because it doesn't have to destroy objects that were never used.
Second, the problem doesn't appear to be in your code snippet. I can use the exact same code and create new forms all day. Judging by the error message, the problem appears to be in the child form itself, not with the parent. You might be doing something that is not allowed in a child form, although I can't fathom what that might be. Its also possible you might have a data binding problem where pages/records/fields are getting locked and a bind is failing on the second form.
You'll have to trace into the creation of the child form to find out whats going on. Set a breakpoint on the Show statement and run your app. When you click on the button to create the new child, the debugger will stop on the Show statement. Hit F11 to step into the child form to see what's going on.
RageInTheMachine9532
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hello
i have written an application to take pictures from a webcam (using APIs) and to save the picture into database.its working fine ...
But when i try to close my application its NOT CLOSING PERFECTLY. some times it hangs too.(expect this problem the application is running smoothly)
i am calling the "EndAppln" procedure in a closebutton_click and in the queryunload event of the main form
please see the code below . . . .
Any one please suggest any changes to be made to my application TO SAFELY CLOSE MY APPLICATION ?.
'***** variables declared in a bas module
Public Const CAP_START = &H400
Public Const CAP_GET_CAPSTREAMPTR = CAP_START + 1
Public Const CAP_SET_CALLBACK_ERROR = CAP_START + 2
Public Const CAP_SET_CALLBACK_STATUS = CAP_START + 3
Public Const CAP_SET_CALLBACK_YIELD = CAP_START + 4
Public Const CAP_SET_CALLBACK_FRAME = CAP_START + 5
Public Const CAP_SET_CALLBACK_VIDEOSTREAM = CAP_START + 6
Public Const CAP_SET_CALLBACK_WAVESTREAM = CAP_START + 7
Public Const CAP_DRIVER_CONNECT = CAP_START + 10
Public Const CAP_DRIVER_DISCONNECT = CAP_START + 11
'*****
private sub EndAppln
' the below given are functions declared a module and called from the main form
capSetCallbackOnError = SendMessage(lwnd,CAP_SET_CALLBACK_ERROR, 0,lpProc)
capSetCallbackOnStatus = SendMessage(lwnd,CAP_SET_CALLBACK_STATUS,0,lpProc)
capSetCallbackOnYield = SendMessage(lwnd,CAP_SET_CALLBACK_YIELD, 0,lpProc)
capSetCallbackOnFrame = SendMessage(lwnd,CAP_SET_CALLBACK_FRAME,0,lpProc)
capSetCallbackOnVideoStream = SendMessage(lwnd,CAP_SET_CALLBACK_VIDEOSTREAM, 0,lpProc)
capSetCallbackOnWaveStream = SendMessage(lwnd,CAP_SET_CALLBACK_WAVESTREAM, 0,lpProc)
capSetCallbackOnCapControl = SendMessage(lwnd,CAP_SET_CALLBACK_CAPCONTROL, 0,lpProc)
''''' end of the callback
DoEvents
capDriverDisconnect (mywdc)
capCaptureStop (mywdc)
DestroyWindow (mywdc) ' the API declared in the bas module
UnLoad Me
End
End Sub
Thanks in advance
Mohan G
Mohan G
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The problem might not be in your application at all. It's possible that it's in the API for the webcam. Usually, something like this happens because not all resources and handles are freed before you quit. Check to make absolutely sure you free all the resources you allocate and close any handles you have and make sure your shutting down the API correctly so it can free up any resources that it has allocated.
After doing that you'd have to get ahold of developer support for the API to find a solution. Hey! Maybe you've found a bug! 
RageInTheMachine9532
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thank you rage
i am puzzled here, how to debug my application exactly. will you please help me to fix this problem.i will send the whole application . ok.
Mohan G
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It's just a thorough code review. If you can eliminate everything YOUR doing as a possible cause, then the cause is in the API your using.
RageInTheMachine9532
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thank you rage
i have gone through my code. I am not good in working with API.This is a simple application (i mean less no. of lines of code).can you please check my code.(this is very urgent for me to fix this problem).so i look forward for an helping hand like you.
Mohan G
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Send it to my email address. I'm also going to need the address to pick up a copy of the SDK your using.
RageInTheMachine9532
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I've saved a few things in strings that I wanted to write...What I am is making a sort of robot for a game I play. The particular part I am working on right now is supposed to be easy for people to use to edit the .ini file.
I've saved a few things in strings that I did not want to continually write in... so heres what It looks like...
Write #1, strSaved.string
Write #2, strSaved2.string
But when I go to run, I get an invalid qualifier message...
what can i do to fix this?
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VB6?
It all depends on how strSaved and strSaved2 are declared. If they are declared as string, which I think they are, then you don't need the ".string" at the end of each variable. If they are declared as TextBoxes, then you use ".Text" instead of ".string" to return the contents of the TextBox.
RageInTheMachine9532
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I've started playing around with connecting a VB 6.0 form to my new SQL server (indeed, I am new to SQL server, as well as it is a new installation) using an ADO control. I've done plenty of connecting to an Access DB with ADO controls and programming, so I figured that trying to connect to SQL was the next logical step. The server installed fine, and the form connected to the server without incident.
However, when I ran the form, I had some major issues. When my textboxes lost focus, the inputs were returned to null strings as though nothing had been entered into the control. I have an assignment statement passing the string in the control to a variable in the Lost Focus event, and stepped through the code with the debugger, and this problem is happening before that line of code is being fired.
I figure it has to be something wrong with my ADO connection, because as soon as I take the control off the form, the problem goes away. I am using the correct connection string, as far as I know (ie the connection for SQL Server). However...I kinda need to be connected to the database for this to be effective 
Any thoughts? Please keep in mind I'm used to connecting to Access but kinda guessing and checking with the SQL server, so ANY input will be helpful.
THX
--------------------
Tim Perry
"Remember, comments are there to make people laugh, not to help them fix your code later...because you're code is always perfect"
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 I want to create a custom form control library but the documentation says the Class Library template is not available in the std edition of VB. Can I Use the New Class or New Module to create these controls and just include the class/module in my project? If yes, Can I add the control to the Forms Designer Toolbox?
Ricks
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The Template your looking for is the Windows Control Library Template. Your right, this template doesn't come with the Standard Edition compiler. You COULD write the code out by hand, but the problem is the Standard Edition compiler won't compile into a .DLL. You can check this by starting a project and clicking on Properties on the Project menu (all the way at the bottom.) Make sure your looking at the General tab on the left, and click on the Output Type dropdown list. If Class Library is not listed, you can't compile controls at all.
RageInTheMachine9532
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how do i control registry on any remote computer on the network, and add/delete/modify keys or values.
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You have to use the OpenRemoteBaseKey function of the RegistryKey class to get a RegistryKey object returned for the key that you want. In order for you to get this connection, both the Client AND Server machines MUST be running the Remote Registry Service AND have Remote Administration enabled. On top of that, you have to have appropriate rights to the target machine registry for what you want to do.
Docs on this can be found here[^].
RageInTheMachine9532
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thank u very much that was a great help
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Dear sir/madam ,
I had a problem in visual basic 6.0.
I would like to crate files at the runtime on VB 6.0 and after that I would like store the same file in the LOB data type provided by the oracle. I am using BLOB for the same and oracle 8i database.
After storing the data to the oracle, I would like to open the same file runtime on the application and then after I like to store the same file on the physical disk.
Application is about creating any type of file at runtime on the from and adding the same file to the database and on the other node I like to open the same and store file on to the physical disk. Mainly we are going to store image file ,PDF, xls. , and Doc files
Kindly provided help on the same.
If you can provide me the method and source code then It would be grate help to me
Looking forward to your immediate reply.
Thanking you in Anticipation
with warm regards.
Yogesh Dwivedi
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outlook2000 is connected Exchange server.
how to open outlook2000 "Contact people" interface use VB code?
thanks
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what do u need help on
Game Tester
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Can I use C++ For video Game Programming. If u can please let me
know or reply
Game Tester
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Yes, but asking in the Visual C++ forum would be more sensible.
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what about visaul basic and i do viedo game programmin g for visual basic and can uu send me an email do so that I can dounload and install msdn libary
Game Tester
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You can't download the MSDN Library unless your a subscriber. In that case you'll get the thing on DVD anyway. The other option is to use the library on the web at http://msdn.microsoft.com/library/default.asp[^].
You can download and install the Platform SDK from here[^]. Be warned - it's a HUGE download...
RageInTheMachine9532
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whats platform SDK
Game Tester
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