Shared Properties disappearing

[Simon]

Hi all,

We have an ASP.NET 1.1 application running on IIS6 on Server 2003.

Most of the base objects we are using in this application are taken from a
windows application also written by us. We have used shared properties on
some of these objects to enable caching of frequently used objects, so save
fetching them from SQL every time. These shared properties vastly increase
performance of our windows app.

So in our web app, we have left the same caching technique, by using shared
properties we cache various objects, usually in collections.

These collections have been strongly typed by utilising seperate classes and
storing an internal collection, e.g. see below.

Public Class AttributeCollec tion

Implements IEnumerable

Protected intCollection As New Collection

Public Overridable Sub Add(ByVal Attr As Attribute)
intCollection.A dd(Attr, Attr.Name)
End Sub

Public Sub Remove(ByVal Attr As Attribute)
intCollection.R emove(Attr.Name )
End Sub

Public Sub Remove(ByVal AttrName As String)
intCollection.R emove(AttrName)
End Sub

Public Function Count() As Integer
Return intCollection.C ount
End Function

Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
Get
Return CType(intCollec tion.Item(AttrN ame), Attribute)
End Get
End Property
Default ReadOnly Property Item(ByVal index As Integer) As Attribute
Get
Return CType(intCollec tion.Item(index ), Attribute)
End Get
End Property

Public Function GetEnumerator() As System.Collecti ons.IEnumerator
Implements System.Collecti ons.IEnumerable .GetEnumerator
Return intCollection.G etEnumerator
End Function


End Class

The problem, is that at certain times, the cached collection returns
containing nothing in the internal collection.

So the shared Property is returning ok, and is pointing to one of the
collections as shown above, however, the intcollection in the above code
contains nothing. so the code falls over. We cannot explain why the internal
collection for these objects is being emptied?

Anyone any ideas?

Thanks in advance and regards,
Simon.

[Milosz Skalecki]

RE: Shared Properties disappearing

Hi there,

This is because web application is being unloaded from appdomain and all
shared variables are lost. Try to not use static memebrs in ASP.NET
applications, use Application state + Application_Sta rt/Application_End
events instead.

Please find detailed explanation of this problem here

http://www.devsource.com/article2/0,1895,1876120,00.asp

--
Milosz Skalecki
MCP, MCAD


"Simon" wrote:
[color=blue]
> Hi all,
>
> We have an ASP.NET 1.1 application running on IIS6 on Server 2003.
>
> Most of the base objects we are using in this application are taken from a
> windows application also written by us. We have used shared properties on
> some of these objects to enable caching of frequently used objects, so save
> fetching them from SQL every time. These shared properties vastly increase
> performance of our windows app.
>
> So in our web app, we have left the same caching technique, by using shared
> properties we cache various objects, usually in collections.
>
> These collections have been strongly typed by utilising seperate classes and
> storing an internal collection, e.g. see below.
>
> Public Class AttributeCollec tion
>
> Implements IEnumerable
>
> Protected intCollection As New Collection
>
> Public Overridable Sub Add(ByVal Attr As Attribute)
> intCollection.A dd(Attr, Attr.Name)
> End Sub
>
> Public Sub Remove(ByVal Attr As Attribute)
> intCollection.R emove(Attr.Name )
> End Sub
>
> Public Sub Remove(ByVal AttrName As String)
> intCollection.R emove(AttrName)
> End Sub
>
> Public Function Count() As Integer
> Return intCollection.C ount
> End Function
>
> Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
> Get
> Return CType(intCollec tion.Item(AttrN ame), Attribute)
> End Get
> End Property
> Default ReadOnly Property Item(ByVal index As Integer) As Attribute
> Get
> Return CType(intCollec tion.Item(index ), Attribute)
> End Get
> End Property
>
> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
> Implements System.Collecti ons.IEnumerable .GetEnumerator
> Return intCollection.G etEnumerator
> End Function
>
>
> End Class
>
> The problem, is that at certain times, the cached collection returns
> containing nothing in the internal collection.
>
> So the shared Property is returning ok, and is pointing to one of the
> collections as shown above, however, the intcollection in the above code
> contains nothing. so the code falls over. We cannot explain why the internal
> collection for these objects is being emptied?
>
> Anyone any ideas?
>
> Thanks in advance and regards,
> Simon.
>
>
>
>[/color]

[Simon]

Re: Shared Properties disappearing

Thanks for the reply Milosz,

I understand your reasoning, but if all shared variables are lost, how come
the reference to the shared collection is working, it is only when it tries
to access the intCollection inside the shared collection class that the
application falls over.

e.g. Taking the collection from below, and putting it in a shared property,
Which is how it is working in our app.

Public Class Attribute

Private Shared _attributes As AttributeCollec tion

Public Shared Sub RefreshCache()

' Code to build the collection in here....

End Sub

Public Shared ReadOnly Property Attributes() As AttributeCollec tion
Get
If _attributes Is Nothing Then
RefreshCache()
End If
Return _attributes
End Get

End Property

End Class

Public Class AttributeCollec tion

Implements IEnumerable

Protected intCollection As New Collection

Public Overridable Sub Add(ByVal Attr As Attribute)
intCollection.A dd(Attr, Attr.Name)
End Sub

Public Sub Remove(ByVal Attr As Attribute)
intCollection.R emove(Attr.Name )
End Sub

Public Sub Remove(ByVal AttrName As String)
intCollection.R emove(AttrName)
End Sub

Public Function Count() As Integer
Return intCollection.C ount
End Function

Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
Get
Return CType(intCollec tion.Item(AttrN ame), Attribute)
End Get
End Property
Default ReadOnly Property Item(ByVal index As Integer) As Attribute
Get
Return CType(intCollec tion.Item(index ), Attribute)
End Get
End Property

Public Function GetEnumerator() As System.Collecti ons.IEnumerator
Implements System.Collecti ons.IEnumerable .GetEnumerator
Return intCollection.G etEnumerator
End Function

Public Function Contains(ByVal attrName As String) As Boolean
For Each attr As Attribute In intCollection
If attr.Name.ToLow er = attrName.ToLowe r Then
Return True
End If
Next
Return False
End Function

End Class


Any code that references Attribute.Attri butes never returns a null
reference, it always appears to return the correct collection object. But
when you then use Attribute.Attri butes.Contains( "name") it falls over in the
contains code. Saying that intcollection is nothing.

Hope you understand more.
And thanks again for your reply.
Simon.


"Milosz Skalecki" <mily242@REMOVE ITwp.pl> wrote in message
news:EE0E0F5D-1CF3-4B76-B7F3-30518EDB7695@mi crosoft.com...[color=blue]
> Hi there,
>
> This is because web application is being unloaded from appdomain and all
> shared variables are lost. Try to not use static memebrs in ASP.NET
> applications, use Application state + Application_Sta rt/Application_End
> events instead.
>
> Please find detailed explanation of this problem here
> http://www.devsource.com/article2/0,1895,1876120,00.asp
> --
> Milosz Skalecki
> MCP, MCAD
>
>
> "Simon" wrote:
>[color=green]
>> Hi all,
>>
>> We have an ASP.NET 1.1 application running on IIS6 on Server 2003.
>>
>> Most of the base objects we are using in this application are taken from
>> a
>> windows application also written by us. We have used shared properties on
>> some of these objects to enable caching of frequently used objects, so
>> save
>> fetching them from SQL every time. These shared properties vastly
>> increase
>> performance of our windows app.
>>
>> So in our web app, we have left the same caching technique, by using
>> shared
>> properties we cache various objects, usually in collections.
>>
>> These collections have been strongly typed by utilising seperate classes
>> and
>> storing an internal collection, e.g. see below.
>>
>> Public Class AttributeCollec tion
>>
>> Implements IEnumerable
>>
>> Protected intCollection As New Collection
>>
>> Public Overridable Sub Add(ByVal Attr As Attribute)
>> intCollection.A dd(Attr, Attr.Name)
>> End Sub
>>
>> Public Sub Remove(ByVal Attr As Attribute)
>> intCollection.R emove(Attr.Name )
>> End Sub
>>
>> Public Sub Remove(ByVal AttrName As String)
>> intCollection.R emove(AttrName)
>> End Sub
>>
>> Public Function Count() As Integer
>> Return intCollection.C ount
>> End Function
>>
>> Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
>> Get
>> Return CType(intCollec tion.Item(AttrN ame), Attribute)
>> End Get
>> End Property
>> Default ReadOnly Property Item(ByVal index As Integer) As Attribute
>> Get
>> Return CType(intCollec tion.Item(index ), Attribute)
>> End Get
>> End Property
>>
>> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
>> Implements System.Collecti ons.IEnumerable .GetEnumerator
>> Return intCollection.G etEnumerator
>> End Function
>>
>>
>> End Class
>>
>> The problem, is that at certain times, the cached collection returns
>> containing nothing in the internal collection.
>>
>> So the shared Property is returning ok, and is pointing to one of the
>> collections as shown above, however, the intcollection in the above code
>> contains nothing. so the code falls over. We cannot explain why the
>> internal
>> collection for these objects is being emptied?
>>
>> Anyone any ideas?
>>
>> Thanks in advance and regards,
>> Simon.
>>
>>
>>
>>[/color][/color]

[Milosz Skalecki]

Re: Shared Properties disappearing

Hi again,

First of all, your code is not thread safe. If you're going to use
static/shared members in multithreading environment (as in ASP.NET) you MUST
make it thread safe (synchronizatio n, locks, etc). Use thread safe singleton
class or what’s quicker, save the time by simply using Application State or
Cache classes that are designed for storing/caching frequently used data in
such environment.

Hope this helps
--
Milosz Skalecki
MCP, MCAD


"Simon" wrote:
[color=blue]
> Thanks for the reply Milosz,
>
> I understand your reasoning, but if all shared variables are lost, how come
> the reference to the shared collection is working, it is only when it tries
> to access the intCollection inside the shared collection class that the
> application falls over.
>
> e.g. Taking the collection from below, and putting it in a shared property,
> Which is how it is working in our app.
>
> Public Class Attribute
>
> Private Shared _attributes As AttributeCollec tion
>
> Public Shared Sub RefreshCache()
>
> ' Code to build the collection in here....
>
> End Sub
>
> Public Shared ReadOnly Property Attributes() As AttributeCollec tion
> Get
> If _attributes Is Nothing Then
> RefreshCache()
> End If
> Return _attributes
> End Get
>
> End Property
>
> End Class
>
> Public Class AttributeCollec tion
>
> Implements IEnumerable
>
> Protected intCollection As New Collection
>
> Public Overridable Sub Add(ByVal Attr As Attribute)
> intCollection.A dd(Attr, Attr.Name)
> End Sub
>
> Public Sub Remove(ByVal Attr As Attribute)
> intCollection.R emove(Attr.Name )
> End Sub
>
> Public Sub Remove(ByVal AttrName As String)
> intCollection.R emove(AttrName)
> End Sub
>
> Public Function Count() As Integer
> Return intCollection.C ount
> End Function
>
> Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
> Get
> Return CType(intCollec tion.Item(AttrN ame), Attribute)
> End Get
> End Property
> Default ReadOnly Property Item(ByVal index As Integer) As Attribute
> Get
> Return CType(intCollec tion.Item(index ), Attribute)
> End Get
> End Property
>
> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
> Implements System.Collecti ons.IEnumerable .GetEnumerator
> Return intCollection.G etEnumerator
> End Function
>
> Public Function Contains(ByVal attrName As String) As Boolean
> For Each attr As Attribute In intCollection
> If attr.Name.ToLow er = attrName.ToLowe r Then
> Return True
> End If
> Next
> Return False
> End Function
>
> End Class
>
>
> Any code that references Attribute.Attri butes never returns a null
> reference, it always appears to return the correct collection object. But
> when you then use Attribute.Attri butes.Contains( "name") it falls over in the
> contains code. Saying that intcollection is nothing.
>
> Hope you understand more.
> And thanks again for your reply.
> Simon.
>
>
> "Milosz Skalecki" <mily242@REMOVE ITwp.pl> wrote in message
> news:EE0E0F5D-1CF3-4B76-B7F3-30518EDB7695@mi crosoft.com...[color=green]
> > Hi there,
> >
> > This is because web application is being unloaded from appdomain and all
> > shared variables are lost. Try to not use static memebrs in ASP.NET
> > applications, use Application state + Application_Sta rt/Application_End
> > events instead.
> >
> > Please find detailed explanation of this problem here
> > http://www.devsource.com/article2/0,1895,1876120,00.asp
> > --
> > Milosz Skalecki
> > MCP, MCAD
> >
> >
> > "Simon" wrote:
> >[color=darkred]
> >> Hi all,
> >>
> >> We have an ASP.NET 1.1 application running on IIS6 on Server 2003.
> >>
> >> Most of the base objects we are using in this application are taken from
> >> a
> >> windows application also written by us. We have used shared properties on
> >> some of these objects to enable caching of frequently used objects, so
> >> save
> >> fetching them from SQL every time. These shared properties vastly
> >> increase
> >> performance of our windows app.
> >>
> >> So in our web app, we have left the same caching technique, by using
> >> shared
> >> properties we cache various objects, usually in collections.
> >>
> >> These collections have been strongly typed by utilising seperate classes
> >> and
> >> storing an internal collection, e.g. see below.
> >>
> >> Public Class AttributeCollec tion
> >>
> >> Implements IEnumerable
> >>
> >> Protected intCollection As New Collection
> >>
> >> Public Overridable Sub Add(ByVal Attr As Attribute)
> >> intCollection.A dd(Attr, Attr.Name)
> >> End Sub
> >>
> >> Public Sub Remove(ByVal Attr As Attribute)
> >> intCollection.R emove(Attr.Name )
> >> End Sub
> >>
> >> Public Sub Remove(ByVal AttrName As String)
> >> intCollection.R emove(AttrName)
> >> End Sub
> >>
> >> Public Function Count() As Integer
> >> Return intCollection.C ount
> >> End Function
> >>
> >> Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
> >> Get
> >> Return CType(intCollec tion.Item(AttrN ame), Attribute)
> >> End Get
> >> End Property
> >> Default ReadOnly Property Item(ByVal index As Integer) As Attribute
> >> Get
> >> Return CType(intCollec tion.Item(index ), Attribute)
> >> End Get
> >> End Property
> >>
> >> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
> >> Implements System.Collecti ons.IEnumerable .GetEnumerator
> >> Return intCollection.G etEnumerator
> >> End Function
> >>
> >>
> >> End Class
> >>
> >> The problem, is that at certain times, the cached collection returns
> >> containing nothing in the internal collection.
> >>
> >> So the shared Property is returning ok, and is pointing to one of the
> >> collections as shown above, however, the intcollection in the above code
> >> contains nothing. so the code falls over. We cannot explain why the
> >> internal
> >> collection for these objects is being emptied?
> >>
> >> Anyone any ideas?
> >>
> >> Thanks in advance and regards,
> >> Simon.
> >>
> >>
> >>
> >>[/color][/color]
>
>
>[/color]

[Simon]

Re: Shared Properties disappearing

Hi Milosz,

Thanks again for taking the time to reply.

So do you think that is the problem, that the classes are not thread safe,
and mutliple thread are possibly writing to the shared properties? and
somehow causing the internal intcollection to be nothing. It sounds
unlikely, but we're clutching at straws here, so are willing to try
anything.

So we wish to ensure that our objects are thread safe, however, these
objects are used in both a windows and an ASP.NET environment.
How is it best to go about making a class that is used in both asp.net and
windows thread safe for both environments?

Regards,
Simon.

"Milosz Skalecki" <mily242@REMOVE ITwp.pl> wrote in message
news:E856044A-2701-49D9-A31A-E06670ABA734@mi crosoft.com...[color=blue]
> Hi again,
>
> First of all, your code is not thread safe. If you're going to use
> static/shared members in multithreading environment (as in ASP.NET) you
> MUST
> make it thread safe (synchronizatio n, locks, etc). Use thread safe
> singleton
> class or what's quicker, save the time by simply using Application State
> or
> Cache classes that are designed for storing/caching frequently used data
> in
> such environment.
>
> Hope this helps
> --
> Milosz Skalecki
> MCP, MCAD
>
>
> "Simon" wrote:
>[color=green]
>> Thanks for the reply Milosz,
>>
>> I understand your reasoning, but if all shared variables are lost, how
>> come
>> the reference to the shared collection is working, it is only when it
>> tries
>> to access the intCollection inside the shared collection class that the
>> application falls over.
>>
>> e.g. Taking the collection from below, and putting it in a shared
>> property,
>> Which is how it is working in our app.
>>
>> Public Class Attribute
>>
>> Private Shared _attributes As AttributeCollec tion
>>
>> Public Shared Sub RefreshCache()
>>
>> ' Code to build the collection in here....
>>
>> End Sub
>>
>> Public Shared ReadOnly Property Attributes() As AttributeCollec tion
>> Get
>> If _attributes Is Nothing Then
>> RefreshCache()
>> End If
>> Return _attributes
>> End Get
>>
>> End Property
>>
>> End Class
>>
>> Public Class AttributeCollec tion
>>
>> Implements IEnumerable
>>
>> Protected intCollection As New Collection
>>
>> Public Overridable Sub Add(ByVal Attr As Attribute)
>> intCollection.A dd(Attr, Attr.Name)
>> End Sub
>>
>> Public Sub Remove(ByVal Attr As Attribute)
>> intCollection.R emove(Attr.Name )
>> End Sub
>>
>> Public Sub Remove(ByVal AttrName As String)
>> intCollection.R emove(AttrName)
>> End Sub
>>
>> Public Function Count() As Integer
>> Return intCollection.C ount
>> End Function
>>
>> Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
>> Get
>> Return CType(intCollec tion.Item(AttrN ame), Attribute)
>> End Get
>> End Property
>> Default ReadOnly Property Item(ByVal index As Integer) As Attribute
>> Get
>> Return CType(intCollec tion.Item(index ), Attribute)
>> End Get
>> End Property
>>
>> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
>> Implements System.Collecti ons.IEnumerable .GetEnumerator
>> Return intCollection.G etEnumerator
>> End Function
>>
>> Public Function Contains(ByVal attrName As String) As Boolean
>> For Each attr As Attribute In intCollection
>> If attr.Name.ToLow er = attrName.ToLowe r Then
>> Return True
>> End If
>> Next
>> Return False
>> End Function
>>
>> End Class
>>
>>
>> Any code that references Attribute.Attri butes never returns a null
>> reference, it always appears to return the correct collection object. But
>> when you then use Attribute.Attri butes.Contains( "name") it falls over in
>> the
>> contains code. Saying that intcollection is nothing.
>>
>> Hope you understand more.
>> And thanks again for your reply.
>> Simon.
>>
>>
>> "Milosz Skalecki" <mily242@REMOVE ITwp.pl> wrote in message
>> news:EE0E0F5D-1CF3-4B76-B7F3-30518EDB7695@mi crosoft.com...[color=darkred]
>> > Hi there,
>> >
>> > This is because web application is being unloaded from appdomain and
>> > all
>> > shared variables are lost. Try to not use static memebrs in ASP.NET
>> > applications, use Application state + Application_Sta rt/Application_End
>> > events instead.
>> >
>> > Please find detailed explanation of this problem here
>> > http://www.devsource.com/article2/0,1895,1876120,00.asp
>> > --
>> > Milosz Skalecki
>> > MCP, MCAD
>> >
>> >
>> > "Simon" wrote:
>> >
>> >> Hi all,
>> >>
>> >> We have an ASP.NET 1.1 application running on IIS6 on Server 2003.
>> >>
>> >> Most of the base objects we are using in this application are taken
>> >> from
>> >> a
>> >> windows application also written by us. We have used shared properties
>> >> on
>> >> some of these objects to enable caching of frequently used objects, so
>> >> save
>> >> fetching them from SQL every time. These shared properties vastly
>> >> increase
>> >> performance of our windows app.
>> >>
>> >> So in our web app, we have left the same caching technique, by using
>> >> shared
>> >> properties we cache various objects, usually in collections.
>> >>
>> >> These collections have been strongly typed by utilising seperate
>> >> classes
>> >> and
>> >> storing an internal collection, e.g. see below.
>> >>
>> >> Public Class AttributeCollec tion
>> >>
>> >> Implements IEnumerable
>> >>
>> >> Protected intCollection As New Collection
>> >>
>> >> Public Overridable Sub Add(ByVal Attr As Attribute)
>> >> intCollection.A dd(Attr, Attr.Name)
>> >> End Sub
>> >>
>> >> Public Sub Remove(ByVal Attr As Attribute)
>> >> intCollection.R emove(Attr.Name )
>> >> End Sub
>> >>
>> >> Public Sub Remove(ByVal AttrName As String)
>> >> intCollection.R emove(AttrName)
>> >> End Sub
>> >>
>> >> Public Function Count() As Integer
>> >> Return intCollection.C ount
>> >> End Function
>> >>
>> >> Default ReadOnly Property Item(ByVal AttrName As String) As
>> >> Attribute
>> >> Get
>> >> Return CType(intCollec tion.Item(AttrN ame), Attribute)
>> >> End Get
>> >> End Property
>> >> Default ReadOnly Property Item(ByVal index As Integer) As
>> >> Attribute
>> >> Get
>> >> Return CType(intCollec tion.Item(index ), Attribute)
>> >> End Get
>> >> End Property
>> >>
>> >> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
>> >> Implements System.Collecti ons.IEnumerable .GetEnumerator
>> >> Return intCollection.G etEnumerator
>> >> End Function
>> >>
>> >>
>> >> End Class
>> >>
>> >> The problem, is that at certain times, the cached collection returns
>> >> containing nothing in the internal collection.
>> >>
>> >> So the shared Property is returning ok, and is pointing to one of the
>> >> collections as shown above, however, the intcollection in the above
>> >> code
>> >> contains nothing. so the code falls over. We cannot explain why the
>> >> internal
>> >> collection for these objects is being emptied?
>> >>
>> >> Anyone any ideas?
>> >>
>> >> Thanks in advance and regards,
>> >> Simon.
>> >>
>> >>
>> >>
>> >>[/color]
>>
>>
>>[/color][/color]

[Milosz Skalecki]

Re: Shared Properties disappearing

Howdy,

In this case I would use thread safe singleton:

http://www.yoda.arachsys.com/csharp/singleton.html

In this article you will find how to create static fields safely in
multithread environment.
Also read final part of the following article:

http://codebetter.com/blogs/steve.hebert/archive/2005/12/16/135697.aspx

Hope this helps
--
Milosz Skalecki
MCP, MCAD


"Simon" wrote:
[color=blue]
> Hi Milosz,
>
> Thanks again for taking the time to reply.
>
> So do you think that is the problem, that the classes are not thread safe,
> and mutliple thread are possibly writing to the shared properties? and
> somehow causing the internal intcollection to be nothing. It sounds
> unlikely, but we're clutching at straws here, so are willing to try
> anything.
>
> So we wish to ensure that our objects are thread safe, however, these
> objects are used in both a windows and an ASP.NET environment.
> How is it best to go about making a class that is used in both asp.net and
> windows thread safe for both environments?
>
> Regards,
> Simon.
>
> "Milosz Skalecki" <mily242@REMOVE ITwp.pl> wrote in message
> news:E856044A-2701-49D9-A31A-E06670ABA734@mi crosoft.com...[color=green]
> > Hi again,
> >
> > First of all, your code is not thread safe. If you're going to use
> > static/shared members in multithreading environment (as in ASP.NET) you
> > MUST
> > make it thread safe (synchronizatio n, locks, etc). Use thread safe
> > singleton
> > class or what's quicker, save the time by simply using Application State
> > or
> > Cache classes that are designed for storing/caching frequently used data
> > in
> > such environment.
> >
> > Hope this helps
> > --
> > Milosz Skalecki
> > MCP, MCAD
> >
> >
> > "Simon" wrote:
> >[color=darkred]
> >> Thanks for the reply Milosz,
> >>
> >> I understand your reasoning, but if all shared variables are lost, how
> >> come
> >> the reference to the shared collection is working, it is only when it
> >> tries
> >> to access the intCollection inside the shared collection class that the
> >> application falls over.
> >>
> >> e.g. Taking the collection from below, and putting it in a shared
> >> property,
> >> Which is how it is working in our app.
> >>
> >> Public Class Attribute
> >>
> >> Private Shared _attributes As AttributeCollec tion
> >>
> >> Public Shared Sub RefreshCache()
> >>
> >> ' Code to build the collection in here....
> >>
> >> End Sub
> >>
> >> Public Shared ReadOnly Property Attributes() As AttributeCollec tion
> >> Get
> >> If _attributes Is Nothing Then
> >> RefreshCache()
> >> End If
> >> Return _attributes
> >> End Get
> >>
> >> End Property
> >>
> >> End Class
> >>
> >> Public Class AttributeCollec tion
> >>
> >> Implements IEnumerable
> >>
> >> Protected intCollection As New Collection
> >>
> >> Public Overridable Sub Add(ByVal Attr As Attribute)
> >> intCollection.A dd(Attr, Attr.Name)
> >> End Sub
> >>
> >> Public Sub Remove(ByVal Attr As Attribute)
> >> intCollection.R emove(Attr.Name )
> >> End Sub
> >>
> >> Public Sub Remove(ByVal AttrName As String)
> >> intCollection.R emove(AttrName)
> >> End Sub
> >>
> >> Public Function Count() As Integer
> >> Return intCollection.C ount
> >> End Function
> >>
> >> Default ReadOnly Property Item(ByVal AttrName As String) As Attribute
> >> Get
> >> Return CType(intCollec tion.Item(AttrN ame), Attribute)
> >> End Get
> >> End Property
> >> Default ReadOnly Property Item(ByVal index As Integer) As Attribute
> >> Get
> >> Return CType(intCollec tion.Item(index ), Attribute)
> >> End Get
> >> End Property
> >>
> >> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
> >> Implements System.Collecti ons.IEnumerable .GetEnumerator
> >> Return intCollection.G etEnumerator
> >> End Function
> >>
> >> Public Function Contains(ByVal attrName As String) As Boolean
> >> For Each attr As Attribute In intCollection
> >> If attr.Name.ToLow er = attrName.ToLowe r Then
> >> Return True
> >> End If
> >> Next
> >> Return False
> >> End Function
> >>
> >> End Class
> >>
> >>
> >> Any code that references Attribute.Attri butes never returns a null
> >> reference, it always appears to return the correct collection object. But
> >> when you then use Attribute.Attri butes.Contains( "name") it falls over in
> >> the
> >> contains code. Saying that intcollection is nothing.
> >>
> >> Hope you understand more.
> >> And thanks again for your reply.
> >> Simon.
> >>
> >>
> >> "Milosz Skalecki" <mily242@REMOVE ITwp.pl> wrote in message
> >> news:EE0E0F5D-1CF3-4B76-B7F3-30518EDB7695@mi crosoft.com...
> >> > Hi there,
> >> >
> >> > This is because web application is being unloaded from appdomain and
> >> > all
> >> > shared variables are lost. Try to not use static memebrs in ASP.NET
> >> > applications, use Application state + Application_Sta rt/Application_End
> >> > events instead.
> >> >
> >> > Please find detailed explanation of this problem here
> >> > http://www.devsource.com/article2/0,1895,1876120,00.asp
> >> > --
> >> > Milosz Skalecki
> >> > MCP, MCAD
> >> >
> >> >
> >> > "Simon" wrote:
> >> >
> >> >> Hi all,
> >> >>
> >> >> We have an ASP.NET 1.1 application running on IIS6 on Server 2003.
> >> >>
> >> >> Most of the base objects we are using in this application are taken
> >> >> from
> >> >> a
> >> >> windows application also written by us. We have used shared properties
> >> >> on
> >> >> some of these objects to enable caching of frequently used objects, so
> >> >> save
> >> >> fetching them from SQL every time. These shared properties vastly
> >> >> increase
> >> >> performance of our windows app.
> >> >>
> >> >> So in our web app, we have left the same caching technique, by using
> >> >> shared
> >> >> properties we cache various objects, usually in collections.
> >> >>
> >> >> These collections have been strongly typed by utilising seperate
> >> >> classes
> >> >> and
> >> >> storing an internal collection, e.g. see below.
> >> >>
> >> >> Public Class AttributeCollec tion
> >> >>
> >> >> Implements IEnumerable
> >> >>
> >> >> Protected intCollection As New Collection
> >> >>
> >> >> Public Overridable Sub Add(ByVal Attr As Attribute)
> >> >> intCollection.A dd(Attr, Attr.Name)
> >> >> End Sub
> >> >>
> >> >> Public Sub Remove(ByVal Attr As Attribute)
> >> >> intCollection.R emove(Attr.Name )
> >> >> End Sub
> >> >>
> >> >> Public Sub Remove(ByVal AttrName As String)
> >> >> intCollection.R emove(AttrName)
> >> >> End Sub
> >> >>
> >> >> Public Function Count() As Integer
> >> >> Return intCollection.C ount
> >> >> End Function
> >> >>
> >> >> Default ReadOnly Property Item(ByVal AttrName As String) As
> >> >> Attribute
> >> >> Get
> >> >> Return CType(intCollec tion.Item(AttrN ame), Attribute)
> >> >> End Get
> >> >> End Property
> >> >> Default ReadOnly Property Item(ByVal index As Integer) As
> >> >> Attribute
> >> >> Get
> >> >> Return CType(intCollec tion.Item(index ), Attribute)
> >> >> End Get
> >> >> End Property
> >> >>
> >> >> Public Function GetEnumerator() As System.Collecti ons.IEnumerator
> >> >> Implements System.Collecti ons.IEnumerable .GetEnumerator
> >> >> Return intCollection.G etEnumerator
> >> >> End Function
> >> >>
> >> >>
> >> >> End Class
> >> >>
> >> >> The problem, is that at certain times, the cached collection returns
> >> >> containing nothing in the internal collection.
> >> >>
> >> >> So the shared Property is returning ok, and is pointing to one of the
> >> >> collections as shown above, however, the intcollection in the above
> >> >> code
> >> >> contains nothing. so the code falls over. We cannot explain why the
> >> >> internal
> >> >> collection for these objects is being emptied?
> >> >>
> >> >> Anyone any ideas?
> >> >>
> >> >> Thanks in advance and regards,
> >> >> Simon.
> >> >>
> >> >>
> >> >>
> >> >>
> >>
> >>
> >>[/color][/color]
>
>
>[/color]