Hi,

Could you try specifying a different SessionStateMode in your web.config as described here?
http://msdn.microsoft.com/en-us/library/ms178586.aspx

The image data is generated and stored in the session state when generating the IMG html that will be sent to the browser, so you should not receive a request for the image before it is generated. However from what I understand, the default InProc SessionStateMode will cause the session data to be unavailable if the balancer sends the ImageGen request to a different server on the farm.

Stoyan

Hi,

The control first saves the image data and afterwards sends an <img> element to the browser:

Session[imageId] = GenerateImage(...);
output.Write(CreateImageMap(...));
output.Write("<img src=ImageGen.aspx...");

So, at the time the browser loads the IMG element whose SRC is set to ImageGen, the image bytes are already in the session state. The session data serialization is synchronous from what I can understand (http://msdn.microsoft.com/en-us/library/aa479041.aspx#aspnetsessionstate_topic3), and it should not be possible the browser to send a GET ImageGen request before the data is actually saved in SQLServer.

Are you by chance creating large diagram images? GDI+ cannot create bitmaps larger than about 3000x3000 pixels, and if your diagrams get larger than that you won't get an image displayed. If that's the case, try setting the MaxImageSize property to make the control split the diagram into several smaller bitmaps.

You might also check if the SQLServer session table has some memory limits set for the serialized session-data fields. If the field max. size seems smaller than the generated bitmaps, try increasing it.

I hope that helps,
Stoyan

I suppose you can take a look at the ASPStateTempSessions table using SqlServer Management Studio. I can see a SessionItemShort and SessionItemLong fields there after running the InstallSqlState script, but am not sure how they are used. Anyway we don't have a working server cluster right now, we'll try to set up one for testing next week.

Stoyan