I have a directory on my site that I keep a bunch of text files in (this
directory is "/poetry/poems/"). The Application keeps the first line of each
of these files in an HttpApplication State variable as a SortedList. When I
add or modify a file in this directory, I want to delete this
HttpApplication State variable. I tried to do this using the following lines
of code in Global.asax.vb:
Private WithEvents poemfilewatcher As New
IO.FileSystemWa tcher(HttpConte xt.Current.Serv er.MapPath("/poetry/poems/"))
Private Sub PoemDirModified (ByVal sender As Object, ByVal e As
System.IO.FileS ystemEventArgs) Handles poemfilewatcher .Changed,
poemfilewatcher .Created, poemfilewatcher .Deleted
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Remove("poeml ist")
HttpContext.Cur rent.Applicatio n.UnLock()
End Sub
Sub Application_Sta rt(ByVal sender As Object, ByVal e As EventArgs)
poemfilewatcher .IncludeSubdire ctories = True
poemfilewatcher .EnableRaisingE vents = True
End Sub
The Function that I use to return this SortedList, whether it is stored in
an HttpApplication State variable or not, is the following, which is also
located in Global.asax.vb:
Public Shared Function GetPoems() As SortedList 'Key=Title, Value=File
If HttpContext.Cur rent.Applicatio n("poemlist") Is Nothing Then
Dim Poems As New SortedList(New CaseInsensitive Comparer)
Dim poemfiles As String() =
System.IO.Direc tory.GetFiles(H ttpContext.Curr ent.Server.MapP ath("/poetry/poems/"))
Dim poemstreamreade r As System.IO.Strea mReader
Poems.Capacity = 50 'Not quite 50 poems, so call Poems.TrimToSiz e()
before caching
For Each poemfile As String In poemfiles
poemstreamreade r = System.IO.File. OpenText(poemfi le)
Poems.Add(poems treamreader.Rea dLine(), poemfile)
poemstreamreade r.Close()
Next
Poems.TrimToSiz e()
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Add("poemlist ", Poems)
HttpContext.Cur rent.Applicatio n.UnLock()
Return Poems
Else
Return CType(HttpConte xt.Current.Appl ication("poemli st"),
SortedList)
End If
End Function
However, when I add, delete, or modify a file in the directory it does not
seem to delete the HttpApplication State variable. Am I forgetting to do
something? Am I doing something wrong? Any help would be appreciated, or
possibly an example that mentions all the necessary & required steps. Thank
you to anyone who can give me any help with this.
--
Nathan Sokalski nj********@hotm ail.com http://www.nathansokalski.com/ 6  1365 
Nathan,
One thing I have learned from using the file system watcher previously
is that sometimes it's events trigger so soon after the file is created
/ modified that any code that references the file could be blocked as
the application that caused the creation / modification event still has
the file locked.
Try putting in a wait command for a few seconds to allow all locks on
the file to be cleared. Also I would specify a filter on the file
system watcher so that any files you don't want in there aren't picked
up.
The other thing is that from looking at your code it is possible the
file watcher could be going out of scope. Try looking at running the
file system watcher in a separate thread which is triggered by the
application start event, and ended by the application end event.
There is another way to implement this type of functionality which
would be to use the configuration sections of the web config, whenever
you add a file to the folder simply add it's first line of text and
filename to your sorted list. ASP.Net does automatically cycle when
the web config has been changed, this will ensure your list is always
updated accordingly, although it does add an extra degree of complexity
/ maintenance.
you have a couple issues.
1) you need to dedicate a thread to the filewatcher. currently you are using
the first request thread. if no request come for a couple a seconds. request
threads come from a pool. if not reused, the thread is killed.
2) you are using HttpContext.Cur rent. this will not be valid unless the the
event is fired while processing a request.
you should start a background thread, pass it a reference to the context,
and process the event.
-- bruce (sqlwork.com)
"Nathan Sokalski" <nj********@hot mail.com> wrote in message
news:uK******** ******@TK2MSFTN GP05.phx.gbl... I have a directory on my site that I keep a bunch of text files in (this
directory is "/poetry/poems/"). The Application keeps the first line of
each of these files in an HttpApplication State variable as a SortedList.
When I add or modify a file in this directory, I want to delete this
HttpApplicatio nState variable. I tried to do this using the following lines
of code in Global.asax.vb:
Private WithEvents poemfilewatcher As New
IO.FileSystemWa tcher(HttpConte xt.Current.Serv er.MapPath("/poetry/poems/"))
Private Sub PoemDirModified (ByVal sender As Object, ByVal e As
System.IO.FileS ystemEventArgs) Handles poemfilewatcher .Changed,
poemfilewatcher .Created, poemfilewatcher .Deleted
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Remove("poeml ist")
HttpContext.Cur rent.Applicatio n.UnLock()
End Sub
Sub Application_Sta rt(ByVal sender As Object, ByVal e As EventArgs)
poemfilewatcher .IncludeSubdire ctories = True
poemfilewatcher .EnableRaisingE vents = True
End Sub
The Function that I use to return this SortedList, whether it is stored in
an HttpApplication State variable or not, is the following, which is also
located in Global.asax.vb:
Public Shared Function GetPoems() As SortedList 'Key=Title, Value=File
If HttpContext.Cur rent.Applicatio n("poemlist") Is Nothing Then
Dim Poems As New SortedList(New CaseInsensitive Comparer)
Dim poemfiles As String() =
System.IO.Direc tory.GetFiles(H ttpContext.Curr ent.Server.MapP ath("/poetry/poems/"))
Dim poemstreamreade r As System.IO.Strea mReader
Poems.Capacity = 50 'Not quite 50 poems, so call Poems.TrimToSiz e()
before caching
For Each poemfile As String In poemfiles
poemstreamreade r = System.IO.File. OpenText(poemfi le)
Poems.Add(poems treamreader.Rea dLine(), poemfile)
poemstreamreade r.Close()
Next
Poems.TrimToSiz e()
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Add("poemlist ", Poems)
HttpContext.Cur rent.Applicatio n.UnLock()
Return Poems
Else
Return CType(HttpConte xt.Current.Appl ication("poemli st"),
SortedList)
End If
End Function
However, when I add, delete, or modify a file in the directory it does not
seem to delete the HttpApplication State variable. Am I forgetting to do
something? Am I doing something wrong? Any help would be appreciated, or
possibly an example that mentions all the necessary & required steps.
Thank you to anyone who can give me any help with this.
--
Nathan Sokalski
nj********@hotm ail.com
http://www.nathansokalski.com/
Those all sound like good, working solutions. I think that the two that I
would probably use one of is either the one about the wait command or the
one about creating a separate thread. However, both of those involve code
that I do not have experience using. The one for the wait command sounds
like it is pretty simple, I just need to see the code to use for it. I have
some experience with threads and what they are, just not in VB.NET, so if
you could show me a basic example of how to use a thread in VB.NET or direct
me to a site with some good examples, I would appreciate it. Thank you SO
MUCH for your help and quick response to this problem. Thanks.
--
Nathan Sokalski nj********@hotm ail.com http://www.nathansokalski.com/
"Peter Johnson" <pe***********@ gmail.com> wrote in message
news:11******** **************@ z34g2000cwc.goo glegroups.com.. . Nathan,
One thing I have learned from using the file system watcher previously
is that sometimes it's events trigger so soon after the file is created
/ modified that any code that references the file could be blocked as
the application that caused the creation / modification event still has
the file locked.
Try putting in a wait command for a few seconds to allow all locks on
the file to be cleared. Also I would specify a filter on the file
system watcher so that any files you don't want in there aren't picked
up.
The other thing is that from looking at your code it is possible the
file watcher could be going out of scope. Try looking at running the
file system watcher in a separate thread which is triggered by the
application start event, and ended by the application end event.
There is another way to implement this type of functionality which
would be to use the configuration sections of the web config, whenever
you add a file to the folder simply add it's first line of text and
filename to your sorted list. ASP.Net does automatically cycle when
the web config has been changed, this will ensure your list is always
updated accordingly, although it does add an extra degree of complexity
/ maintenance.
Nathan,
The wait command should be used in tandem with creating a separate
thread. As it would happen to any thread the event is triggered upon.
Hard to believe but microsoft wrote the file system watcher and it is
Uber Efficient!!
Bruce has hit the nail on the head with creating a new thread so that
the file system watcher remains in scope regardless of the context of
the application. I'm unsure on how to implement the threading within
the web application, i've only done threading in windows services.
The responses that you and Peter have given me both seem like very good
advice, but like I have said, I don't really have any experience using
threads in VB.NET. This fact combined with what you have said about the
event needing to be fired while processing a request when used with ASP.NET
is making it kind of hard for me to figure out what to do about figuring out
a solution. Do you have any suggestions/ideas/recommended sites that could
help? Thanks.
--
Nathan Sokalski nj********@hotm ail.com http://www.nathansokalski.com/
"bruce barker (sqlwork.com)" <b_************ *************@s qlwork.com> wrote
in message news:%2******** ********@TK2MSF TNGP02.phx.gbl. .. you have a couple issues.
1) you need to dedicate a thread to the filewatcher. currently you are
using the first request thread. if no request come for a couple a seconds.
request threads come from a pool. if not reused, the thread is killed.
2) you are using HttpContext.Cur rent. this will not be valid unless the
the event is fired while processing a request.
you should start a background thread, pass it a reference to the context,
and process the event.
-- bruce (sqlwork.com)
"Nathan Sokalski" <nj********@hot mail.com> wrote in message
news:uK******** ******@TK2MSFTN GP05.phx.gbl...I have a directory on my site that I keep a bunch of text files in (this
directory is "/poetry/poems/"). The Application keeps the first line of
each of these files in an HttpApplication State variable as a SortedList.
When I add or modify a file in this directory, I want to delete this
HttpApplicati onState variable. I tried to do this using the following
lines of code in Global.asax.vb:
Private WithEvents poemfilewatcher As New
IO.FileSystemWa tcher(HttpConte xt.Current.Serv er.MapPath("/poetry/poems/"))
Private Sub PoemDirModified (ByVal sender As Object, ByVal e As
System.IO.FileS ystemEventArgs) Handles poemfilewatcher .Changed,
poemfilewatcher .Created, poemfilewatcher .Deleted
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Remove("poeml ist")
HttpContext.Cur rent.Applicatio n.UnLock()
End Sub
Sub Application_Sta rt(ByVal sender As Object, ByVal e As EventArgs)
poemfilewatcher .IncludeSubdire ctories = True
poemfilewatcher .EnableRaisingE vents = True
End Sub
The Function that I use to return this SortedList, whether it is stored
in an HttpApplication State variable or not, is the following, which is
also located in Global.asax.vb:
Public Shared Function GetPoems() As SortedList 'Key=Title, Value=File
If HttpContext.Cur rent.Applicatio n("poemlist") Is Nothing Then
Dim Poems As New SortedList(New CaseInsensitive Comparer)
Dim poemfiles As String() =
System.IO.Direc tory.GetFiles(H ttpContext.Curr ent.Server.MapP ath("/poetry/poems/"))
Dim poemstreamreade r As System.IO.Strea mReader
Poems.Capacity = 50 'Not quite 50 poems, so call
Poems.TrimToSiz e() before caching
For Each poemfile As String In poemfiles
poemstreamreade r = System.IO.File. OpenText(poemfi le)
Poems.Add(poems treamreader.Rea dLine(), poemfile)
poemstreamreade r.Close()
Next
Poems.TrimToSiz e()
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Add("poemlist ", Poems)
HttpContext.Cur rent.Applicatio n.UnLock()
Return Poems
Else
Return CType(HttpConte xt.Current.Appl ication("poemli st"),
SortedList)
End If
End Function
However, when I add, delete, or modify a file in the directory it does
not seem to delete the HttpApplication State variable. Am I forgetting to
do something? Am I doing something wrong? Any help would be appreciated,
or possibly an example that mentions all the necessary & required steps.
Thank you to anyone who can give me any help with this.
--
Nathan Sokalski
nj********@hotm ail.com
http://www.nathansokalski.com/
> The responses that you and Peter have given me
If you wouldn't post to so many irrelevant groups, someone might have a clue
as to what Peter's response was.
microsoft.publi c.dotnet.framew ork.adonet,
microsoft.publi c.dotnet.framew ork.aspnet,
microsoft.publi c.dotnet.framew ork.aspnet.buil dingcontrols,
microsoft.publi c.dotnet.framew ork.aspnet.webc ontrols,
microsoft.publi c.dotnet.genera l,
microsoft.publi c.dotnet.l -> Apparently, you've reached some sort of limit
here
Bob Lehmann
"Nathan Sokalski" <nj********@hot mail.com> wrote in message
news:ug******** ******@TK2MSFTN GP05.phx.gbl... The responses that you and Peter have given me both seem like very good
advice, but like I have said, I don't really have any experience using
threads in VB.NET. This fact combined with what you have said about the
event needing to be fired while processing a request when used with
ASP.NET is making it kind of hard for me to figure out what to do about figuring
out a solution. Do you have any suggestions/ideas/recommended sites that could
help? Thanks.
--
Nathan Sokalski
nj********@hotm ail.com
http://www.nathansokalski.com/
"bruce barker (sqlwork.com)" <b_************ *************@s qlwork.com>
wrote in message news:%2******** ********@TK2MSF TNGP02.phx.gbl. .. you have a couple issues.
1) you need to dedicate a thread to the filewatcher. currently you are
using the first request thread. if no request come for a couple a
seconds. request threads come from a pool. if not reused, the thread is killed.
2) you are using HttpContext.Cur rent. this will not be valid unless the
the event is fired while processing a request.
you should start a background thread, pass it a reference to the
context, and process the event.
-- bruce (sqlwork.com)
"Nathan Sokalski" <nj********@hot mail.com> wrote in message
news:uK******** ******@TK2MSFTN GP05.phx.gbl...I have a directory on my site that I keep a bunch of text files in (this
directory is "/poetry/poems/"). The Application keeps the first line of
each of these files in an HttpApplication State variable as a SortedList.
When I add or modify a file in this directory, I want to delete this
HttpApplicati onState variable. I tried to do this using the following
lines of code in Global.asax.vb:
Private WithEvents poemfilewatcher As New
IO.FileSystemWa tcher(HttpConte xt.Current.Serv er.MapPath("/poetry/poems/"))
Private Sub PoemDirModified (ByVal sender As Object, ByVal e As
System.IO.FileS ystemEventArgs) Handles poemfilewatcher .Changed,
poemfilewatcher .Created, poemfilewatcher .Deleted
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Remove("poeml ist")
HttpContext.Cur rent.Applicatio n.UnLock()
End Sub
Sub Application_Sta rt(ByVal sender As Object, ByVal e As EventArgs)
poemfilewatcher .IncludeSubdire ctories = True
poemfilewatcher .EnableRaisingE vents = True
End Sub
The Function that I use to return this SortedList, whether it is stored
in an HttpApplication State variable or not, is the following, which is
also located in Global.asax.vb:
Public Shared Function GetPoems() As SortedList 'Key=Title, Value=File
If HttpContext.Cur rent.Applicatio n("poemlist") Is Nothing Then
Dim Poems As New SortedList(New CaseInsensitive Comparer)
Dim poemfiles As String() =
System.IO.Direc tory.GetFiles(H ttpContext.Curr ent.Server.MapP ath("/poetry/poe
ms/")) Dim poemstreamreade r As System.IO.Strea mReader
Poems.Capacity = 50 'Not quite 50 poems, so call
Poems.TrimToSiz e() before caching
For Each poemfile As String In poemfiles
poemstreamreade r = System.IO.File. OpenText(poemfi le)
Poems.Add(poems treamreader.Rea dLine(), poemfile)
poemstreamreade r.Close()
Next
Poems.TrimToSiz e()
HttpContext.Cur rent.Applicatio n.Lock()
HttpContext.Cur rent.Applicatio n.Add("poemlist ", Poems)
HttpContext.Cur rent.Applicatio n.UnLock()
Return Poems
Else
Return CType(HttpConte xt.Current.Appl ication("poemli st"),
SortedList)
End If
End Function
However, when I add, delete, or modify a file in the directory it does
not seem to delete the HttpApplication State variable. Am I forgetting
to do something? Am I doing something wrong? Any help would be
appreciated, or possibly an example that mentions all the necessary & required
steps. Thank you to anyone who can give me any help with this.
--
Nathan Sokalski
nj********@hotm ail.com
http://www.nathansokalski.com/
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