Environment Variables Go "Poof"

[Scott McNair]

Hi,

I'm trying to set an environment variable programmatically. I've added
these three lines to my code:

System.Environment.SetEnvironmentVariable("TCS", "C:\Program Files\TCS\")
InstallPath = System.Environment.GetEnvironmentVariable("TCS")
MsgBox(InstallPath)

And, as expected, the MsgBox contains "C:\Program Files\TCS\".

However the variable seems to exist only for that instance of the app. For
example, if I open a cmd window while the app is running and type "echo %
TCS%", it just returns "%TCS%". If I exit the app, remark out the first
line, and then re-run the app, the MsgBox returns an empty box.

I'm guessing that any environment variables you set using
System.Environment.SetEnvironmentVariable are volatile; that is, they don't
exist outside that currently running application.

How can I set it programmatically, and have it STAY there?

Regards,
Scott

[Andrew Backer]

Take a look at this, which might help you. It may come down to updating
the registry.

http://ghouston.blogspot.com/2005/08...vironment.html

Hi,

I'm trying to set an environment variable programmatically. I've
added these three lines to my code:

System.Environment.SetEnvironmentVariable("TCS", "C:\Program
Files\TCS\") InstallPath =
System.Environment.GetEnvironmentVariable("TCS") MsgBox(InstallPath)

And, as expected, the MsgBox contains "C:\Program Files\TCS\".

However the variable seems to exist only for that instance of the app.
For example, if I open a cmd window while the app is running and type
"echo % TCS%", it just returns "%TCS%". If I exit the app, remark out
the first line, and then re-run the app, the MsgBox returns an empty
box.

I'm guessing that any environment variables you set using
System.Environment.SetEnvironmentVariable are volatile; that is, they
don't exist outside that currently running application.

How can I set it programmatically, and have it STAY there?

Regards,
Scott

[Scott McNair]

Tom Shelton <to*********@YOUKNOWTHEDRILLcomcast.netwrote in
news:uX**************@TK2MSFTNGP05.phx.gbl:

If you have any issues let me know and I'll actually look up
SendMessage and test some code :)

Thanks, Tom.

I entered your code, and it seems to hang when I use SendMessage.

[Tom Shelton]

On 2008-03-06, Scott McNair <sm*****@beachexpress.takethispartout.comwrote:

Tom Shelton <to*********@YOUKNOWTHEDRILLcomcast.netwrote in
news:uX**************@TK2MSFTNGP05.phx.gbl:

>If you have any issues let me know and I'll actually look up
SendMessage and test some code :)

Thanks, Tom.

I entered your code, and it seems to hang when I use SendMessage.

I tested it here just now - and it is working. The call can take
a few moments, because it has to notify all the top level windows on the
system - and SendMessage will wait for all to return...

Are us sure it is hanging permanetly?
--
Tom Shelton

[Scott McNair]

Scott McNair <sm*****@beachexpress.takethispartout.comwrote in
news:Xn*********************************@207.46.24 8.16:

Just to make sure, I started the app and let it sit there, to see how
long it would take (if ever) to execute. So far it's been sitting for
about ten minutes.

As a followup:

Rather than run the app in debug mode has I had been doing, I compiled it
as a release, and then ran that app. It ran within a second, but it
returned nothing in the MsgBox that supposedly is polling the environment
variable.

I then ran it again, and it returned the proper string in the MsgBox. I
then went into the app and disabled the code that sets the variable,
effectively having the MsgBox be my first line; it still reported the
variable.

So I decided to run it again. I deleted the value from the registry and
reran the application. This time it reported the value properly on the
first execution.

I continued my experiment. I deleted the key and I remarked everything
out. I recompiled the app, and ran it. It still reported the key. "No
problem," I thought, "it just hasn't sent the environment refresh."

So this time I left the registry write remarked, but I unremarked the
SendMessage line. I ran it again, and it STILL reported C:\Program Files
\TCS\ as the value of the variable, even though it shouldn't be there.

The only explanation I can think of is that the SendMessage command only
updates and inserts, but it doesn't actually clear removed items from the
current environment.

Does that sound about right?

[Scott McNair]

Scott McNair <sm*****@beachexpress.takethispartout.comwrote in
news:Xn**********************************@207.46.2 48.16:

The only explanation I can think of is that the SendMessage command
only updates and inserts, but it doesn't actually clear removed items
from the current environment.

Yet more followup:

If I run the app and declare the variable, it does not see the variable
within that instance of the app. I set a timer for five seconds to enable
immediately after SendMessage, and then MsgBoxed the variable; it showed a
blank.

If I then uncomment the code that creates the variable, and recompile the
app, the variable is there when I run it.

I'm guessing that's not typical execution, but I've run it about three or
four times, with the same result each time.

[Tom Shelton]

On 2008-03-06, Scott McNair <sm*****@beachexpress.takethispartout.comwrote:

Scott McNair <sm*****@beachexpress.takethispartout.comwrote in
news:Xn**********************************@207.46.2 48.16:

>The only explanation I can think of is that the SendMessage command
only updates and inserts, but it doesn't actually clear removed items
from the current environment.

Yet more followup:

If I run the app and declare the variable, it does not see the variable
within that instance of the app. I set a timer for five seconds to enable
immediately after SendMessage, and then MsgBoxed the variable; it showed a
blank.

If I then uncomment the code that creates the variable, and recompile the
app, the variable is there when I run it.

I'm guessing that's not typical execution, but I've run it about three or
four times, with the same result each time.

Scott... I can play with this a little more - but, I want to ask before
we go much further (probably should have done this first!), but what is
the ultimate goal here? We maybe going down the wrong road :)

--
Tom Shelton

[Scott McNair]

Tom Shelton <to*********@comcast.netwrote in news:928f4a03-d99d-4d8b-
93***************@d62g2000hsf.googlegroups.com:

Kind of rough, but it seems to work ok :) At least on XP - I suspect
you might have permission issues on Vista ;)

Thank you :)