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Really, the user shouldn't be entering Primary Key values. They should either be autogenerated and/or built from fields in the data, otherwise known as a compound Key. Part of this reason isn't necessarily because of the possibility of duplicate keys, but getting the keys entered consistantly.
The only way to verify that the new Key doesn't exist is to look it up in the database and see if it returns anything. Performance can become an issue if your table contains a large number of rows and/or you don't have your index built correctly.
Dave Kreskowiak
Microsoft MVP - Visual Basic
-- modified at 22:43 Thursday 29th June, 2006
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thanks.
two month ago i was working on a project for a small bussiness, i validate a "IDNO" field by using table search for new number. that table had only 140 records. but the most important issue is the performance in such a large tables with 10000 or above records.
thanks.
-- modified at 15:18 Friday 30th June, 2006
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Hi again to Alex@UEA and other nice helpers:
I am making a prototype for my dissertation. The prototype is expected to have a view ( form) similar to the MS Access "Relationship" view.
Question in details:
1. Brief background/requirements. In my form/view, there may be one to many floating stuffs (e.g. controls/forms/thumbnails), which can be linked through drag-and-drop. A link between these stuffs is presented using a "line" (chart). User can arrange floating stuffs into a fancy layout. When move a floating stuff, the linking line is able to move, yet snap the two related stuffs automatically.
2. My solution. Floating stuffs are to be implemented with floating forms or withevent controls which are allowed to drop/move. The linking line is drawn using System.Drawing functions.
3. Question point: How to make the linking line automatically snap to floating stuffs? More advanced if possible, the line can go round other stuffs on the way when it's moving?
Can any genius advise me with a shortcut to implement this described above?
Or indicate a code sample reference? Thanks a lot.
abc
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While I have to spend much time in figuring out the codes, it really is a good reference. Thanks anyway.
abc
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Is there a way to get Visual Basic to read a file and tell you how many lines with text are in the file?
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Sure. All you have to do is open the file and call ReadLine until it fails. With each read, increment a counter.
BTW: This question reeks of homework...
Dave Kreskowiak
Microsoft MVP - Visual Basic
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hellow to all
i am looking for a way tp patch my program for updates on other computers , is there any way to creat it ?
thxxx
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That depends on what you mean by "patch". The tools that come with Visual Studio offer very limited "patch" support. Basically, it only supports upgrading the entire installation of a previously installed package. Anything else and you'll have to either manually make changes to the .MSI package using something like Microsoft's Orca, or use Wise for Windows Installer, Install Shield, Advanced Installer, or some other professional MSI authoring package.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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I have a window service which is using a web service.
Now the window service is calling a web service function after a particular interval, so eash time a new web service object is created.
Is there a way i can use a single object but since it's a web service function the problem is if i use a single object then it will retain the previous request values which i dont want.
Can anyone help?
Thanx in advance
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I need PGP implementation in .Net. Also from where to download PGP.
punam
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What's wrong with typing PGP VB.NET into Google[^]?
Dave Kreskowiak
Microsoft MVP - Visual Basic
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I am relatively new to the VB.NET environment (comming from C/C++/C#) and need to do some code maintenace.
I am currently trying to find the Pre and Post build steps in the compiler options but have had no luck.
Do they exist?
Thanks in Advance
Paul
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Select menu "Project properties"
Select tab "Compile"
Press button "Build events" and a dialog appears for you to enter pre and post build events.
'--8<------------------------
Ex Datis:
Duncan Jones
Merrion Computing Ltd
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If you're using VB 2003 they don't exist but there is an MS add-in that provides them.
Kevin
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I have an application that is supposed to post data to a servlet (possibly written in java?) by using HTTP:POST
The servlet wants a form filled in which has two text fields and a file upload field e.g.
<form id="ServletTest" method="post">
<input id="Username" name="Username" type="text" />
<input id="Password" maxlength="100" name="Password" type="text" />
<input id="theFile" name="theFile" type="file" />
<input id="SubmitButton" type="submit" value="submit" />
</form>
Unfortunately the servlet is not yet developed, so I need to emulate this behaviour to test my code.
When it is created I will be using something like:-
Dim webReq As WebRequest = WebRequest.Create(My.Settings.ServletURL)
With webReq
.Method = "POST" 'set the request method to POST
.ContentType = "multipart/form-data"
End With
Dim newStream As Stream
Try
newStream = webReq.GetRequestStream()
Catch exPV As ProtocolViolationException
My.Application.Log.WriteException(exPV)
Return False
Exit Function
Catch exW As WebException
'Pass this exception on to the caller to decide what to do with it,
'as it may indicate a temporary problem
Throw
Catch ex As Exception
My.Application.Log.WriteException(ex)
Return False
Exit Function
End Try
How would I create an application that my code can run against to post this form to?
'--8<------------------------
Ex Datis:
Duncan Jones
Merrion Computing Ltd
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Hi,everybody
A difficulty happens to me when i programming.I heartly need your help.
My program is:
i read datas from a test equipment once per 100ms.At the same time,i draw this data to coordinate.As follow:
Private Sub Timer1_Elapsed(ByVal sender As System.Object, ByVal e As System.Timers.ElapsedEventArgs) Handles Timer1.Elapsed
tg = Me.Panel1.CreateGraphics
' tg.TranslateTransform(xtran, ytran)
'tg.ScaleTransform(xscaletran, yscaletran)
xaxis2 += 5.0 ' x coordinate add 5 pixles once
yaxis2 = Tesle() * 10 ' tesle() is a function reading data from
'test equipment
rwrecord += 1
tg.DrawLine(dpen, xaxis, -yaxis, xaxis2, -yaxis2)
xaxis = xaxis2
yaxis = yaxis2
xredraw(rwrecord) = xaxis
yredraw(rwrecord) = yaxis
tg.Dispose()
End Sub
Private Sub Tesle()
Dim inbuffer As String
Do
inbuffer = AxMSComm1.Input
Loop Until InStr(inbuffer, vbCr)
Dim readdata As String
Dim istart As Integer
Dim mstart As Integer
Try
istart = inbuffer.IndexOf("-")
mstart = inbuffer.IndexOf("+")
If istart < 0 Then
Tesle = inbuffer.Substring(mstart, 8)
Else
Tesle = inbuffer.Substring(istart, 8)
End If
Catch ex As Exception
End Try
End Sub
Above is the main code.If i do nothing(such as moving the form),it will draw chart exactly.But when i moved the form(any action activate paint event),It will not draw the point at that time point.after paint event over,it will draw chart well.
i have do something to debug the problem.i find that when form paint event activated.the data read from test equiment is null.here the problem is.
And now i want to get your help.How can i sove the problem.
Waitting for your reply.
Any reply will be appreciated
ICQ:258-235-734
MSN:msnadair@hotmail.com
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The solution is surprisingly simple. Don't draw on the Panel surface. Draw to a Bitmap object that same size as the panel. Set the BackgroundImage property of the panel to the Bitmap. now, when you draw on the Bitmap, just call Refresh on the Panel.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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Thank you for your reply.
Do you think the issue is on the "drawing"????
I think it is on the reading data from test equipment.
when i moving(or other actions) form.at the time i am releasing left mouse,the data readed from test equipment is null.
So i think the issue is between timer_elapsed event and communicating between pc and test equipment.
when i am doing form events,the communication will not happen.but the timer is going on. So the fucntion tesle() returns value 0.Here the problem is.
and also,i have a test.i set the timer.interval to 300 or more.the problem will not happen.
And now if it as i am saying.How can i resolve it.
Best gardness!
ICQ:258-235-734
MSN:msnadair@hotmail.com
-- modified at 21:07 Thursday 29th June, 2006
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First, you're doing some drawing in a Timer event. Don't! Any drawing you do to the screen should be done only in the Paint event.
Second, you're using a Timer out of the ToolBox?? This passes its Timer Tick as an event, which is routed through the app's message pump. This means that other events can pile up VERY rapidly before the Timer Tick event, such as moving the form. Using an event based Timer isn't really a good idea.
Also, 100ms doesn't leave your code very much time to do anything. Painting can take an eternity (>100ms) if not done correctly.
While you're collecting data, draw to a Bitmap. Then you don't have to worry about painting, and repainting, old data continously. You paint your data once on the Bitmap and it'll be persisted between Paint events.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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Thank you for your reply heartly!
Well.i will try to do some changes as follow:
1> take the drawing action out of timer event
2> I havn't drawn graphics to bitmap before.but i will try.
By the way.what does this sentence mean?
Dave Kreskowiak wrote: you're using a Timer out of the ToolBox??
I am using the timer control from toolbox.it is a system.timer but windows.forms.timer.
ICQ:258-235-734
MSN:msnadair@hotmail.com
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codeadair wrote: I am using the timer control from toolbox.it is a system.timer but windows.forms.timer.
This is the Timer I was asking about. It's not the most accurate and it's event can be bogged down by other events the form has to process.
Dave Kreskowiak
Microsoft MVP - Visual Basic
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I agree with you.
And now i am using doublebuffer method.It is really very useful .
But it is going on.and now i have to work off.
I believe i could do well to resolve the problem with your help.
Thank you very much for you help.Please follow the problem.
By the way.what's your time now?
ICQ:258-235-734
MSN:msnadair@hotmail.com
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codeadair wrote: By the way.what's your time now?
To you, it's comming up on Saturday. I'm still on Friday morning.
Dave Kreskowiak
Microsoft MVP - Visual Basic
-- modified at 9:51 Friday 30th June, 2006
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