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Problem when caching chart in Session variable

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I have a very puzzling problem. After I have create my chart, loaded the

template, set up the axes and populated it with data I save the chart object

in a Session variable as follows:

Session("chart") = ChartFx1

Each time a request is made to the web server the chart is updated and

re-displayed. Everything ok up to this point...

Then, if the user waits for 10 minutes and then makes another request to the

server the following message is displayed:

"QueryInterface for interface ChartfxLib.IChartFX failed"

Whilst attempting to perform the following line of code:

ChartFx1.Volume = 70

Any ideas?

Regards, Nick


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1) Your syntax is incorrect, to add an object to a session you must write:

set Session("chart") = ChartFx1

2) It is not a good idea to put a chart object in a session variable as

Chart FX is marked as "apartment-threaded". The following is an excerpt from


"Session scope objects: Objects marked Both will give you the best

performance. Using single-threaded or apartment-threaded objects will cause

the Web server to lock the session down to one thread. Free-threaded objects

do not lock down the session, but are slow"



Software FX, Inc.

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