Accessing ASP.NET Cache from multiple threads

[Michael Vanhoutte]

I was wondering how multiple threads can access the ASP.NET cache object
safely. Take for example the following code that I got from the ASP.NET Cache
object documentation:

DataView Source = (DataView)Cache["MyData1"];
if (Source == null) {
// Connecting to a database...
// Filling a dataset...

Source = new DataView(ds.Tab les["Authors"]);
Cache["MyData1"] = Source;
}
MyDataGrid.Data Source=Source;
MyDataGrid.Data Bind();


The following questions come to my mind:
1. What happens if two threads reach the 'if (source == null)'-line
simultaneously.
They could both start refilling the cache. Do I need to use locks or mutexes
myself if I want to prevent that?

2. Suppose that thread 1 executed the 'if (source2 == null)' line and found
that that source2 wasn't null. What if thread 2 executed
'Cache.Remove(" MyData1")' after thread 1 performed that test but before it
had to change to actually use the value in MyData1.

I would grealy appreciate any feedback!
Michael

[Michael Vanhoutte]

RE: Accessing ASP.NET Cache from multiple threads

I just replied myself so that it is also posted in
dotnet.framewor k.aspnet.cachin g. This newsgroups was probably a better place
to post this question. This was my question:

I was wondering how multiple threads can access the ASP.NET cache object
safely. Take for example the following code that I got from the ASP.NET Cache
object documentation:

DataView Source = (DataView)Cache["MyData1"];
if (Source == null) {
// Connecting to a database...
// Filling a dataset...

Source = new DataView(ds.Tab les["Authors"]);
Cache["MyData1"] = Source;
}
MyDataGrid.Data Source=Source;
MyDataGrid.Data Bind();


The following questions come to my mind:
1. What happens if two threads reach the 'if (source == null)'-line
simultaneously.
They could both start refilling the cache. Do I need to use locks or mutexes
myself if I want to prevent that?

2. Suppose that thread 1 executed the 'if (source2 == null)' line and found
that that source2 wasn't null. What if thread 2 executed
'Cache.Remove(" MyData1")' after thread 1 performed that test but before it
had to change to actually use the value in MyData1.

I would grealy appreciate any feedback!
Michael

[joker]

Re: Accessing ASP.NET Cache from multiple threads

This news group is for classic ASP none of the .net stuff. I'd suggest
posting in a newsgroup that includes .net in the name for .net problems.

Michael Vanhoutte wrote:
[color=blue]
> I just replied myself so that it is also posted in
> dotnet.framewor k.aspnet.cachin g. This newsgroups was probably a better place
> to post this question. This was my question:
>
> I was wondering how multiple threads can access the ASP.NET cache object
> safely. Take for example the following code that I got from the ASP.NET Cache
> object documentation:
>
> DataView Source = (DataView)Cache["MyData1"];
> if (Source == null) {
> // Connecting to a database...
> // Filling a dataset...
>
> Source = new DataView(ds.Tab les["Authors"]);
> Cache["MyData1"] = Source;
> }
> MyDataGrid.Data Source=Source;
> MyDataGrid.Data Bind();
>
>
> The following questions come to my mind:
> 1. What happens if two threads reach the 'if (source == null)'-line
> simultaneously.
> They could both start refilling the cache. Do I need to use locks or mutexes
> myself if I want to prevent that?
>
> 2. Suppose that thread 1 executed the 'if (source2 == null)' line and found
> that that source2 wasn't null. What if thread 2 executed
> 'Cache.Remove(" MyData1")' after thread 1 performed that test but before it
> had to change to actually use the value in MyData1.
>
> I would grealy appreciate any feedback!
> Michael[/color]