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I am quoting a clear example of the Junction table, in Northwind sample database.
When employing this database in a DataGrid, I receive DataConstraint Exception Error in the Junction table "Order Details" or in the "Orders" table, with the following error message:
"Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints."
On displaying one of the errant tables, each row complains as below:
"ForeignKeyConstraint, Shipper_Order (for example) requires the child key values ????? to exist in the parent table.
NOTES:
1- I established Relations just according to the ones in MS Access application.
2- The Same Database is Functioning normally inside MS Access application.
3- I am mainly concerned about the Junction table.
I need professional guidance as this is a study project, I am working on.
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is it possible to develop a GUI designer that will generate code in java using vb?
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Yes, but you'll have to supply all the code for writing the Java code and stringing it together properly for creating your UI. The .NET Framework doesn't have anything to do it for you.
Your next stop should be Google and "java UI designer source". But with all the ones that currently exist, why would you want to reinvent the wheel, again?
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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1.How can I allocate memory(dinamic) in vb 6?
2. How can I create aLinked List in VB 6?
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1. Depends on what you mean by "allocate memory dynamically", and what you're using it for. VB6 doesn't have anything to allocate memory like C/C++ can, and doesn't support pointers like it either.
2. Easy. Google for "vb6 linked list[^]".
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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Hi everybody
I wrote a program in Vb.Net, it can open a text file (*.txt). But I don't know how to make my program that when I click on any text file (*.txt) then my program will run and open this text file.
Vo Duy Hien
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Set that up in your folder options under file types. For the txt file type set your program to open instead of notepad or whatever.
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Dear all
I am New to Vb.net
i want to add item in database , by entring data in datagrid.Grid should show one row at startup and when I press Another Key Like down Arrow , Then New Row must be Shown to insert the item .
please suggest me how it can be do.
Can VB.net support another third party grid.
Thanks in Advance
Tusar
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Fill your dataset, create a dataview based on row number in dataset, bind dataview to datagrid. In KeyUp event, +/- row selection.
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Hi gurus
I have a newbie question
I have a test plan for the mechanical device, which look a bit like
1. measure this voltage
2. write down the color of the wire
2.1 ....
2.2 ....
3. etc
I would like to create the front end, which would diplay the plan from the excel spreadsheet and allow technician to respond to the items of the plan. Sometimes technician must put the yes/no answer and sometimes put the comment as a result of the test.
I don't want to invent bisycle and assume somebody already done this. Could you point me to the good article/book or ready made program for fulfilling such task?
I put the question into VB forum, because my research up to now shows that such ready-made-program doesn't exist and I will need to write one.
Shura
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I'm writing a class project in visual studio 2003.
Part of the data used by the classes is stored in xml files that the user will be able to edit.
The classes are used by other applications and an end user could have more than one of these applications on their machine.
How do I distribute the classes so that they know where to find the xml data files every time and they are only saved once.
I had originally used the Application.StartupPath to find the folder where the class dll file is stored but, when I create another application the value returned by Application.StartupPath doesn't return the folder where the xml data files are stored it returns (quite rightly) the folder of the original application.
Any idea on how I go about distributing and accessing these xml files?
Any help would be gratefully received as this is a project I intend to open up on a 'do-what-you-want' licence without copyright and for all to use.
Thanks in advance
An optimist's glass is half full.
A pesimist's glass is half empty.
An engineer goes and gets the right size glass.
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Hi All
Its a very simple code.
Project has 3 forms. On load of the first form say Form1 I am creating a new thread. Under this thread I am intitializing the timers of Form2. And then show a different form say Form3 using showdialog
but I am not able to understand why doent the timer event of the timers present on Form2 gets called inspite of being intialized under the start of the thread.
Please help me to find the reason why doesnt this code work
See the code below
Public Class Form1<br />
Inherits System.Windows.Forms.Form<br />
Public NewThread As System.Threading.Thread<br />
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load<br />
NewThread = New Threading.Thread(AddressOf StartNewThread)<br />
NewThread.Start()<br />
<br />
Dim objFrm As New Form3<br />
objFrm.ShowDialog()<br />
End Sub<br />
Private Sub StartNewThread()<br />
Dim obj As New Form2<br />
While True<br />
If (obj.Timer1.Enabled = False) Then<br />
obj.Timer1.Start()<br />
End If<br />
If (obj.Timer2.Enabled = False) Then<br />
obj.Timer2.Start()<br />
End If<br />
End While<br />
End Sub<br />
End Class<br />
<br />
<br />
Public Class Form2<br />
Inherits System.Windows.Forms.Form<br />
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick<br />
MsgBox("Inside timer event of timer1")<br />
End Sub<br />
<br />
Private Sub Timer2_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer2.Tick<br />
MsgBox("inside timer event of TIMER2")<br />
End Sub<br />
End Class<br />
<br />
<br />
Public Class Form3<br />
Inherits System.Windows.Forms.Form<br />
Private Sub Form3_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load<br />
Application.DoEvents()<br />
End Sub<br />
End Class
Thanks,
~VanitaJ
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Well, I've never put Form's-based Timers in other threads. In theory, though, they're not working because the Timer Tick events are not getting to the forms because those forms are on seperate threads from the main UI thread of your application.
In the example code you've posted, there is no need for seperate threads at all. You shouldn't be putting different forms on seperate threads. All your forms go on the UI thread, while background work goes into seperate threads and uses Invoke method calls back to their parent forms to have the forms update themselves with new data.
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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Thanks Dave.
I have to achieve something similar. Hence trying out a small example with 3 forms.
~VanitaJ
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How can I set focus on a TextBox in a given row in a DataGrid?
Thanks
-- modified at 8:51 Monday 5th December, 2005
Or How can I change the Tabstop propery to false on certain column in a Datagrid?
I've tried this but it does not work.
grdColumnStyle2.TextBox.TabStop = False
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I want to use the serial port to flash a led. Is there a simple way to acces the serial port.
Al I want is a snippet that can put a signal on the serial port where the led is connected
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The serial port is a poor choice to do this because you would have to constantly raise a signal to keep the LED lite. The parallel port is a much better choice and there are plenty of examples on how to do it.
Also, there is no "easy" way to do this. Low-level hardware control is beyond the ability of VB.NET or C# code alone. You need a .DLL that runs inside Ring 0 (device drivers) to handle the hardware for you.
You can find a pretty good example of parallel port control at http://www.logix4u.net. For more than that, just Google for "VB parallel LED".
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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Thanks, but ...
The parallel port is already in use.
The only thing i have to do is after pressing a button on the screen send a single pulse to the serial port for opening a lock. I have a opto coupler for saftey, so a single flash from the led is all it takes.
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The problem with that is the pulse comming from the serial port usually isn't long enough to allow an LED to completely illuminate.
You can TRY this (lifted from Experts Exchange):
MSComm1.CommPort = 1 'select your com port either 1 or 2 or 3 if you have it
MSComm1.Settings = "9600,n,8,1" 'this must be configured to your specifications
'9600 is the baud rate, n is no parity bits, 8 data bits and 1 stop bit
MSComm1.PortOpen = True 'opens the port
End Sub
'To send data from the com port
Private Sub cmdSend_Click()
MSComm1.Output = "111111111111111"
End Sub
It uses the old MSCOMM control from the VB6 days. There's virtually no examples of doing this, because of the problems with using the serial port to do anything useful with an LED.
RageInTheMachine9532
"...a pungent, ghastly, stinky piece of cheese!" -- The Roaming Gnome
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You could use a microcontroller and send data via the rs232 port!
I don’t know your electronics abilities, but a simple PIC16F84 or PIC16F628 would be suitable, you can even use BASIC to program the PIC. Just create a basic selection program and control it via VB.NET.
Trust me there are thousands of examples on the net!
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Hello,
I am coding a text editor program. I creat my main form with a menu. While the user hit a menu item, a different form would come out and ask for input. After that, I would like the change reflected in the main form, say, TextBox1 in the main form.
Can somebody give suggestions?
Best,
Hui
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Different way of accomplishing it.
Common one, and easiest, is:
sub form1clickwhattever....
form2.show
me.textbox1.text = form2.controlwithdata.text
end sub
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Thanks for the reply. I tried to use the code in my program. However, it does not work. I would like the me.textbox1.text get changed after the user click on an OK button in the 2nd form. The code above replaces the textbox1.text with a blank string, since the user has not filled out the info yet. I guess that I need to refer to the caller (main form) in the called form (child form), but I don't know how to refer to the main form in the child form. In Visual Basic 6, I think I can just call its name but not in Visual Basic .Net. Any suggestions?
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Well my code has an error or better it was missing the form2.showdialog (so that the next line is executed only after the form2 has been hidden/closed with the button).
So if you replace .show with .showdialog then it works.
Anyway if you want a more precise answer you should provide more precise informations. Which versione of FW are you using 1.x or 2? VS2003 or VS2005.
In VS2003 you can refer to the calling form only if it's public declared.
Module x
public fmain as new frmMain
end module
then in the form2 button click event handler:
fmain.textbox1.text = ....
In VS2005 in most cases you can state immediatly the form without instancing it. This means you can have a direct access to frmMain (considering the previous example) unless you're running an instance created by you (than you fallback in the former case).
Another way of doing it is by raising an event.
In form2 you'll have:
...
raisevevent OKClicked()
and in form1
private sub ClickOnForm2() handles frm2.OKClicked
me.textbox1.text = frm2.textbox1.text
end sub
or using parameters ...
public class frm2eventargs
inherits eventargs
public t as string
end class
on form2 before you raise the event...
dim e as new frm2eventargs
e.t = (text to pass)
raiseevent OKClicked(me,e)
and then on the mainform
private sub frm2OKClick(sender as object,e as frm2eventargs) handles frm2.OKClicked
me.textbox1.text = t
end sub
So as you can see lot of options depending on the approach you want and what you're using.
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