[dba-VB] VB.Net "proxy" progress indicator

Hello John,

If you're sure your main code export/import will never be used in
multi-threading scenarios then you can just use so called Delegates...

But I'd propose you to try to implement multi-threading and use
BackGroundWorker class - they both could help you to solve your task
effectively and have your tasks completed quicker because of multi-threading
- have a look at this article/book excerpt:

http://www.albahari.com/threading/part3.html#_BackgroundWorker 

--
Shamil
 
-----Original Message-----
From: dba-vb-bounces at databaseadvisors.com
[mailto:dba-vb-bounces at databaseadvisors.com] On Behalf Of jwcolby
Sent: Wednesday, December 26, 2007 7:05 PM
To: dba-vb at databaseadvisors.com
Subject: [dba-VB] VB.Net "proxy" progress indicator

I am trying to figure out how to do something that is probably simple if I
knew what I was doing.

I have a bunch of processes that do similar things.  They need to visually
report the same data.  For example I import CSV or flat files from a
directory of files.  Thus I need to report:

1) The directory being processed
2) The current file name
3) File N of M being processed
4) A "progress bar" showing that something is happening in the current file
5) The NAME of the process currently running

I also EXPORT CSV files from a table out to a directory.  I need to report:

1) The directory being exported to
2) The current file name
3) File N of M being exported
4) A "progress bar" showing that something is happening in the current file
5) The NAME of the process currently running

As you can see, though the direction is different, and the class that
performs the process is different, they both need to report the same kind of
things.

So what I want to do is create a progress form that has controls and labels
for the controls to display this information.  I would like to make the form
not required for the process itself to run, i.e. I can display the progress
if I so desire or not show the progress.  All progress is also being logged
to tables and text files thus the display is a "nice to have" feature.  

My concept of how to do that is with events, i.e. the class that performs
the process raises a series of events, and if there is a listener, then the
listener displays the information.  For example The process raises a
"Process Name" event and passes out the name of the process it is running.
It then determines how many files will be required and raises a "Total
Files" event passing out the N (number of files) value.  It has a counter by
which it tracks which file it is currently processing and raises an M
(current file number) event every time it starts a file.  It raises a
"Current File name" event as it generates the file name it is about to
process.  And so forth.

Then a "proxy" progress indicator form can be opened.  This is where my
knowledge breaks down.  Somehow I have to pass in a "something" that can
have its events processed.  The problem is that the "something" changes.
One time it is a CSVExport class, the next it is a CSVImport class, the next
time it is a FlatFileExport class, the next it is a FlatFileImport class.

Now given my weak knowledge of VB.Net, my first thought is to create a
"clsProxySource" as a base class.  This class has properties for holding
these pieces of data (process name, M, N, FileName etc) and methods which
raise events and pass out these variables.  I then inherit this
clsProxySource" in each of my process classes so that each of those process
classes has the properties and the ability to raise this event.

Next in the proxy display form I dimension a variable mclsProxySource of
type clsProxySource.  I define the event sinks for the events that the
clsProxySource sources.  In the New() I pass in the process class instance
that needs to display a status.  In the new it is coerced back into a
clsProxySource and stored in the mclsProxySource.

Now the process class can raise events and the form (if it exists) sinks
those events and displays the values in the controls on the form.

So... Is that how it is done, and if not how do I go about doing this?  If
it is how it is done, the one piece I know for sure that I am missing id the
syntax for coercing the process class back into the clsProxySource.  

If anyone could help me with this stuff I would be most appreciative.

Thanks,

John W. Colby
Colby Consulting
www.ColbyConsulting.com 

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