Anyone have any idea why this code does not work?
FileOpen(1, "c:\JUNK\MYTEST .TXT", OpenMode.Binary ,
OpenAccess.Read Write, OpenShare.Share d)
Dim X As Integer
For X = 1 To 26
FilePut(1, Chr(X + 64))
Next
Lock(1, 5, 10)
When it hits the lock I get this message:
An unhandled exception of type 'System.Argumen tOutOfRangeExce ption' occurred
in mscorlib.dll
Additional information: Non-negative number required.
I ran into this problem in a program I'm trying to port from VB6. I created
this simplified code to illustrate the problem.
Does VB.Net not support file locking????
Gary
14  3823 
Gary,
A couple of things I noticed
(a) Why would you lock a series of records you just inserted. It seems to
me that you would only lock these records if you were to edit them. Based
on your code it appears that the file is opened for sequential access and
according to the help:
"If the file has been opened for sequential input or output, Lock and Unlock
affect the entire file, regardless of the range specified by FromRecord and
ToRecord."
If you change your code to open in Random mode you should not have a problem
locking
FileOpen(filenu m, "c:\temp\mytest .txt", OpenMode.Random ,
OpenAccess.Read Write, OpenShare.Share d)
(b) If you really need to lock records you may want to consider using a
database instead of a file.
Good Luck,
Dan
"Gary Nelson" <gn@contanet.es > wrote in message
news:%2******** ********@TK2MSF TNGP12.phx.gbl. .. Anyone have any idea why this code does not work?
FileOpen(1, "c:\JUNK\MYTEST .TXT", OpenMode.Binary ,
OpenAccess.Read Write, OpenShare.Share d)
Dim X As Integer
For X = 1 To 26
FilePut(1, Chr(X + 64))
Next
Lock(1, 5, 10)
When it hits the lock I get this message:
An unhandled exception of type 'System.Argumen tOutOfRangeExce ption'
occurred in mscorlib.dll
Additional information: Non-negative number required.
I ran into this problem in a program I'm trying to port from VB6. I
created this simplified code to illustrate the problem.
Does VB.Net not support file locking????
Gary
Hi Gary,
Thanks for using Microsoft MSDN Managed Newsgroup. My name is Peter, and I
will be assisting you on this issue.
First of all, I would like to confirm my understanding of your issue.
From your description, I understand that when you Open File as
OpenMode.Binary and want to lock the file from 5 to 10 record(byte). and
you get error.
Have I fully understood you? If there is anything I misunderstood, please
feel free to let me know.
I think this is by design, if you really want to do so, you may need to
open the file as OpenMode.Random as solex suggest.
Best regards,
Peter Huang
Microsoft Online Partner Support
Get Secure! - www.microsoft.com/security
This posting is provided "AS IS" with no warranties, and confers no rights.
Dan, (a) Why would you lock a series of records you just inserted.
As I stated: "I ran into this problem in a program I'm trying to port from
VB6. I created
this simplified code to illustrate the problem."
The reason I inserted data was to illustrate that it wasn't an empty file,
or I wasn't trying to lock beyond the eof.
It seems to
me that you would only lock these records if you were to edit them.
Obviously. And only when multiple users are attacking the data
simultaneously.
Based
on your code it appears that the file is opened for sequential access
Wrong. Look again. The file is being opened for Binary access.
and
according to the help:
"If the file has been opened for sequential input or output, Lock and
Unlock affect the entire file, regardless of the range specified by FromRecord
and ToRecord."
If that were the case, Lock would lock the whole file, not return an error.
If you change your code to open in Random mode you should not have a
problem locking
Random mode won't do. I am dealing with binary data. I want to lock a series
of bytes, which the help files says CAN be done.
(b) If you really need to lock records you may want to consider using a
database instead of a file.
What I want can not be handled by Access nor SQL.
Gary
Peter,
Thanks for your answer. First of all, I would like to confirm my understanding of your issue.
From your description, I understand that when you Open File as
OpenMode.Binary and want to lock the file from 5 to 10 record(byte). and
you get error.
Exactly. This is a simplified example of what I need to do, but if you
execute the code you will see what happens.
Have I fully understood you? If there is anything I misunderstood, please
feel free to let me know.
You have understood.
I think this is by design, if you really want to do so, you may need to
open the file as OpenMode.Random as solex suggest.
It is clearly NOT by design. The help file clearly states:
Parameters
FileNumber
Required. Any valid file number.
FromRecord
Optional. Number of the first record or byte to lock or unlock.
ToRecord
Optional. Number of the last record or byte to lock or unlock.
Note that it clearly mentions "first record or BYTE" and "last record or
BYTE"
Also further down in the help file, the example given is this:
FileOpen(1, "c:\people.txt" , OpenMode.Binary )
Why would the example show OpenMode.Binary if Lock can not handle binary
files?
Also the help file mentions as exceptions the following:
Exceptions/Errors
Exception type Error number Condition
IOException 52 FileNumber does not exist.
IOException 54 File mode is invalid.
I am not getting either of these exceptions, therefore I assume that it must
be a bug in VB.Net.
And on the other hand Random is no good for my purpose. In the situation I
am working on right now I am dealing with a binary file which at a certain
position has a double precision number which must be locked, read, added to,
and unlocked.As the file is accessed by multiple users simultaneously. Any
failure on the lock will produce incorrect results, therefore not locking is
not an alternative.
By the way, this worked perfectly with VB6.
Gary
"Gary Nelson" <gn@contanet.es > schrieb I think this is by design, if you really want to do so, you may
need to open the file as OpenMode.Random as solex suggest.
It is clearly NOT by design. The help file clearly states:
I can't help you, just want to let you know that I also think it is not by
design. I also think it should work. I don't know why the negative values
are calculated. It also works in VB6.
--
Armin http://www.plig.net/nnq/nquote.html http://www.netmeister.org/news/learn2quote.html
On Tue, 20 Jan 2004 10:52:45 -0000, Gary Nelson wrote:
Does VB.Net not support file locking????
Just a thought, could the Lock method depend on the position of the file
pointer? Perhaps if you tried to seek back to the beginning of the file
before attempting the lock. Also, what if you close and then reopen the
file before attempting the lock.
Finally, I notice that your hardcoding the file handle. Perhaps it would
be batter to call freefile. Maybe file handle number 1 is already in use.
Have you verified that the file was inded created and the correct data
exists in it?
It looks like it should work the way you have it. Hope these ideas can
help a little.
--
Chris
To send me an E-mail, remove the underscores and lunchmeat from my E-Mail
address.
Gary,
After looking further into this out of curiosity I decided to try the
example in the docs under "Lock, Unlock" and there is a problem in the docs,
they use the FilePut function incorrectly, at least according to the docs
the FilePut overloaded functions all begin with the FileNumber and in the
example they are using some record index.
I am also trying to read the data back but cannot seem to get it to work
according to the docs under "Seek" the FileGet is supposed to accept a
structure as a parameter but in my IDE I get the error "Overload Resolution
Failed" Sample provided below.
Anyway I have included a modified example that appears to work, I ran it
from 2 different project in the IDE and I can write records at the same time
as long as the recNum paramaters are different. If I attempt to write the
same record number an error is generated as expected.
Out of curiosity what is it that you are trying to do that a database could
not do?
Regards,
Dan
<Sample Code>
Structure Person
Dim Name As String
Dim ID As Integer
End Structure
Public Sub Test()
InsertData(1)
End Sub
Public Sub InsertData(ByVa l recNum As Integer)
Dim x As New Person
x.Name = "Chuck Kiedra"
x.ID = 13
PutInLockedFile (recNum, x)
x = Nothing
End Sub
Public Sub PutInLockedFile (ByVal index As Integer, ByVal onePerson As
Person)
Try
Dim filenum As Integer = FreeFile()
If index > 1 Then index *= Len(onePerson)
FileOpen(filenu m, "c:\temp\people .txt", OpenMode.Binary , _
OpenAccess.Read Write, OpenShare.Share d)
Lock(filenum, index)
FilePut(filenum , onePerson, index)
Unlock(filenum, index)
FileClose(filen um)
Catch ex As Exception
MsgBox(ex.ToStr ing)
End Try
End Sub
Public Sub ReadData()
Dim onePerson As Person
Try
Dim filenum As Integer = FreeFile()
FileOpen(filenu m, "c:\temp\people .txt", OpenMode.Binary , _
OpenAccess.Read Write, OpenShare.Share d)
Seek(filenum,1)
' the following line will not compile
FileGet(filenum , onePerson)
Debug.WriteLine (onePerson.ID, onePerson.Name)
FileClose(filen um)
Catch ex As Exception
MsgBox(ex.ToStr ing)
End Try
End Sub
</Sample Code>
"Gary Nelson" <gn@contanet.es > wrote in message
news:OU******** ******@TK2MSFTN GP10.phx.gbl... Dan,
(a) Why would you lock a series of records you just inserted.
As I stated: "I ran into this problem in a program I'm trying to port
from VB6. I created
this simplified code to illustrate the problem."
The reason I inserted data was to illustrate that it wasn't an empty file,
or I wasn't trying to lock beyond the eof.
It seems to
me that you would only lock these records if you were to edit them.
Obviously. And only when multiple users are attacking the data
simultaneously.
Based
on your code it appears that the file is opened for sequential access
Wrong. Look again. The file is being opened for Binary access.
and
according to the help:
"If the file has been opened for sequential input or output, Lock and
Unlock affect the entire file, regardless of the range specified by FromRecord
and ToRecord."
If that were the case, Lock would lock the whole file, not return an
error. If you change your code to open in Random mode you should not have a problem locking
Random mode won't do. I am dealing with binary data. I want to lock a
series of bytes, which the help files says CAN be done.
(b) If you really need to lock records you may want to consider using a
database instead of a file.
What I want can not be handled by Access nor SQL.
Gary
Dan, I am also trying to read the data back but cannot seem to get it to work
according to the docs under "Seek" the FileGet is supposed to accept a
structure as a parameter but in my IDE I get the error "Overload
Resolution Failed" Sample provided below.
Option Strict Off
Anyway I have included a modified example that appears to work
The problem is that you are only locking the first byte, not the whole
series of bytes you are writing to.
Out of curiosity what is it that you are trying to do that a database
could not do?
There are a lot of things you can do much more efficiently with a binary
file than with a database.
If you want to add a lot of speed to your programs do a little experimenting
with binary files.
Gary
Chris, Just a thought, could the Lock method depend on the position of the file
pointer?
No
Perhaps if you tried to seek back to the beginning of the file
before attempting the lock.
No. Besides the fact that it doesn't change a thing, it would be a waste of
tiime.
Also, what if you close and then reopen the
file before attempting the lock.
Another waste of time, which by the way does not make a bit of difference.
It still doesn't work.
Finally, I notice that your hardcoding the file handle. Perhaps it would
be batter to call freefile. Maybe file handle number 1 is already in use.
As I stated in my post: "I created this simplified code to illustrate the
problem."
If you examine the code, you'll see that no files are open. Besides, the
error is not produced when the file is opened. The error occurs on the lock.
Have you verified that the file was inded created and the correct data
exists in it?
Yes.
It looks like it should work the way you have it.
It should.
Hope these ideas can help a little.
Not much. Personally I think it's a bug in VB.Net.
Gary This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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