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.Tables["Authors"]);
Cache["MyData1"] = Source;
}
MyDataGrid.DataSource=Source;
MyDataGrid.DataBind();


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]

I just replied myself so that it is also posted in
dotnet.framework.aspnet.caching. 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.Tables["Authors"]);
Cache["MyData1"] = Source;
}
MyDataGrid.DataSource=Source;
MyDataGrid.DataBind();


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]

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.