Re: Multiple user accessing single DB - C# Discussion Boards

OriginalGriff16-Jun-09 1:11

16-Jun-09 1:11

Or use ReadAllLines to read each file into a string array and then loop though with nested foreach loops.

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Le centriste16-Jun-09 2:18

Le centriste

16-Jun-09 2:18

Luc Pattyn wrote:
Your try-finally construct will swallow any exception that may occur

Are you sure? Since the catch is missing, the finally block will be executed and the exception rethrown, no?

Luc Pattyn16-Jun-09 2:42

Luc Pattyn

16-Jun-09 2:42

Hi,

my mistake, you are right, try-finally without catch does not influence exception throwing/catching at all.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

Multiple user accessing single DB

kallileo16-Jun-09 2:46

kallileo

16-Jun-09 2:46

Thank you guys...
I did what Luc said and it worked.

Hum Dum16-Jun-09 0:50

Hum Dum

16-Jun-09 0:50

Hello to everybody....

I have developed an application in C# which one is intended to interact with a database file. Well, as it is not supposed to be a large and complex database, I chose to work with MS Access. So far so good.....

Now, my application is already developed and the database as well, but the following issue came out to my mind: whether it would be possible a multi-user access to be performed upon the database. The number of users is expected to be up to 10.

How to use same MDB file over LAN network, and performing operation parallely from multiple users.

Any article/hint or clue will be highly appreciated and exceptionally helpful! Smile | :)

regards

Tom Deketelaere16-Jun-09 1:22

Tom Deketelaere

16-Jun-09 1:22

Hum Dum wrote:
How to use same MDB file over LAN network

Place the db on a place that is accessible for all the pc's in the network (that use your program).
Then you need to alter you connectionstring so that it points to the path where the db is.

Where it comes to locks and performance, it depends on how you'v written your program.
Access isn't the best solution for a multi user environment. And depending on how you'v written your code it could cause db locks or strange behavior when more than 1 user is altering the same data.
Only testing will tell you that.

Hum Dum16-Jun-09 18:55

Hum Dum

16-Jun-09 18:55

thanks for reply.

Tom Deketelaere wrote:
need to alter you connectionstring

can i use open dialog box control, so that user can locate the MDB file for 1st time, then store this path on local pc for next uses.
Is it correct way?

Tom Deketelaere wrote:
And depending on how you'v written your code it could cause db locks

I am using DataAdapter, then uploading all data in datasets, datatable, then updating back the changes back to original DB as user updates.

Its very helpful of your if you point out to some article or reading stuff, as i know very little about distributed/client-server environment.

I want to know in detail.

regards

Tom Deketelaere16-Jun-09 21:09

Tom Deketelaere

16-Jun-09 21:09

Hum Dum wrote:
can i use open dialog box control, so that user can locate the MDB file for 1st time, then store this path on local pc for next uses.
Is it correct way?

That would be the best way yes.
To store the path you can use the settings file (go to project properties --> tab settings).

As to the db locks and such, if there only be 10 users the changes of something going wrong are small, but like others have said you might want to consider going to a different server (sql-express), performance will be better and possible locks are handled better.
If you are staying with access, you might want to consider creating a service or a small tool to 'repair and compress' the database, since it will grow with every update/insert/delete you do.

I don't know of any articles so can't link to them.

Nagy Vilmos16-Jun-09 2:35

Nagy Vilmos

16-Jun-09 2:35

Further to Tom's reply, if the data layer is seperate to the client, it would be better to have an process running locally to the server that can manage the access to the Access DB. With ~10 users it is unlikely, unless it is for data entry, to hit concurrency problems.

A better solution would be to look at migrating the database to one which supports multiple users.

Panic, Chaos, Destruction.
My work here is done.

Hum Dum16-Jun-09 18:58

Hum Dum

16-Jun-09 18:58

thanks for reply.

will you plz point me to some article or website from where i can gain the required knowledge?

about server-client approach i know very little.

OriginalGriff16-Jun-09 4:40

controling cells in TableLayoutPanel

16-Jun-09 4:40

Further to Nagys' reply, it is worth planning for the future. If it is intended for 10 users, then plan for 30! Access is not brilliant at multi-user, and you may find bandwidth problems if the DB gets large (as the query is executed at the local machine, rather than on the server hosting the DB.)
I would sugest a client - server approach would be appropriate - nothing too complex, but have a server app to interface with the DB and keep all unnecessary data off the network. This also allows you to control concurrency issues better than just letting several apps access the same DB directly.

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samy10016-Jun-09 0:43

samy100

16-Jun-09 0:43

Hi,

i am trying to do a matrix (2X3 cells) in which i want to set each cell to be with different backcolor and text , and to be able to detect a click event on a cell so i could change the cell backcolor and text.

can i do it wuth the TableLayoutPanel control? how?

thanks,
Samy

Re: controling cells in TableLayoutPanel

OriginalGriff16-Jun-09 1:05

Remote Desktop Connection

16-Jun-09 1:05

samy100 wrote:
can i do it wuth the TableLayoutPanel control

Yes.

samy100 wrote:
how?

Create your panel, with the rows and columns you want.
Add a label control to each, and set its Dock property to Fill.
Set its TextAlign property to MiddleCenter.

Set each label Click event to the same click handler.
Make your click event look like this:

private void label_Click(object sender, EventArgs e)
    {
    if (sender is Label)
        {
        Label lab = sender as Label;
        if (lab.BackColor == Color.Red)
            {
            lab.BackColor = Color.AntiqueWhite;
            lab.Text = "Hello";
            }
        else
            {
            lab.BackColor = Color.Red;
            lab.Text = "Goodbye";
            }
        }
    }

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singhdurgesh16-Jun-09 0:17

singhdurgesh

16-Jun-09 0:17

We want to open an FTP link in remote desktop machine?
after opening the link we need file information on the FTP link.

How would that happen?

Any help would be appreciated........

Thanks

Re: Remote Desktop Connection [modified]

Baran M16-Jun-09 1:38

Baran M

16-Jun-09 1:38

do you need to get some files from the remote machine ? if so you could directly put ftp commands in a file and you can run it like,

open machine name
username
password
get a.txt
bye

why are you trying to open a link in the relate machine

Education is not a way to escape poverty — it is a way of fighting it.

modified on Tuesday, June 16, 2009 7:46 AM

singhdurgesh16-Jun-09 1:56

singhdurgesh

16-Jun-09 1:56

Thanks,

we have requirement to open an FTP link which can only be run in remote machines(any port setting is there perhaps).

Baran M16-Jun-09 2:03

Baran M

16-Jun-09 2:03

what do you mean by opening a FTP link in remote machine ?

Education is not a way to escape poverty — it is a way of fighting it.

singhdurgesh16-Jun-09 2:17

singhdurgesh

16-Jun-09 2:17

We have to access a file and that file is on a ftp location and that ftp location can only be accessed by remotely connected server.So the steps that we need to take is as :

1-Remote connection to a server

2-after RMC connect to ftp.

3-check the modified date of a file on ftp location.

I think It calrifies all your doubts.

Thanks,

Tracking number of a given object stored in memory

Baran M16-Jun-09 2:38

Baran M

16-Jun-09 2:38

As far as I know you can keep a binary or a script on a remote machine which can access the server and ftp the new file to the remote machine.

Education is not a way to escape poverty — it is a way of fighting it.

Nil_IQ15-Jun-09 23:59

Nil_IQ

15-Jun-09 23:59

Hi,

I'm trying to debug a smallish application which crashes approximately every 10 days with an out of memory exception. Specifically, i've established that the problem lies within a single thread, and I suspect I know which object is causing the problem, but I need to find out when copies of this object are being added and removed from the memory.

If this is not possible, could I perhaps have some general pointers as to when an object is generally added and removed from memory? I realise of course that what is likely happening isn't the application running out of physical memory, but running out of address space, but understanding the problem is getting me no closer to a solution!

Any help would be appreciated,

Thanks,

Nil

Re: Tracking number of a given object stored in memory [modified]

Luc Pattyn16-Jun-09 0:22

Luc Pattyn

16-Jun-09 0:22

Hi,

proper use of try-catch blocks should pinpoint the problem.
I know of three ways to get an OOM Exception:

1.
the most surprising one: some methods throw OOM on bad inputs, most notoriously: Image.FromFile().

2.
you are really running out of memory; typically that means you are preventing objects from being collected. You can watch your app grow, roughly through Task Manager; more correctly by incorporating a display of Environment.WorkingSet in your app.

One way of keeping objects around is by storing references to lots of, or all, objects you create; maybe for debugging, for statistical information, as a cache, whatever. If so, consider the WeakReference class.

3.
you have objects larger than 80KB; those get allocated on the "large-object-heap", which never gets compacted, and hence could become fragmented, resulting in an OOM even when lots of free memory is still around (but each chunk is smaller than the size needed).

Remember: lots of collections (ArrayList, List< T>, etc) are stored as arrays, and such arrays get doubled in size and copied each time their capacity gets exceeded.
IMO you can't reliably design a long running .NET app if you need large objects, unless you:
- either make them all the same size;
- or perform the entire memory management for large objects yourself.
Both of which may be tedious. A third possibility is making your app restart periodically all by itself.

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles]

DISCLAIMER: this message may have been modified by others; it may no longer reflect what I intended, and may contain bad advice; use at your own risk and with extreme care.

modified on Tuesday, June 16, 2009 6:33 AM

Re: Tracking number of a given object stored in memory

OriginalGriff16-Jun-09 1:14