I have a MDI win forms application in c# that I am writing.

I don't think I have implemented very good session management.

In my application, a user can have more than one page open at a time. (Pages are child winform objects). So on one page, the user could be creating a new Foo object while on another page the user could be updating a Bar object. When the user saves his new Foo object, any edits made to the Bar object are flushed. I don't want changes to the Bar object flushed, though. Each page needs to be savable seperatly.

I know the problem is because I am using one session for all of my application. I can see why this is bad, now.

But my question is, what is the best way to do this? Should each page have its own session? That is my first thought, but before i go down that road, I wanted to get some feedback. Can I even have multiple sessions open at the same time?

Is there a way to have an MDI application or will I really have to change and make the user work on "one thing a a time"

Thanks for any advice or tips...

Brian

I have setup a session manager to issue a new session to each of my MDI child forms.

But when I try to save, I am getting a NullReferenceException.

This exception occurs when I try to commit my transaction after a SaveOrUpdate() call.

The object I am saving has a many-to-one property called LastUpdatedBy that identifies the user who change the object.

When trying to save that property, it throws the exception.

It is thrown from NHibernate.Engine.Cascades.VersionValue.IsUnsaved(object version)

The line that throws the exception:


This is because "version" = 5, but "value" is null. So the first part returns false but the value.Equals() throws an exception because value is null.

The object I am trying to save is not unsaved. (iow, it was loaded from the database via a QBE query)




Any hints on what might be wrong here?? I am using NHibernate 1.2.0.Alpha1.

I have the same problem. For now I am ending the session every time I save or delete. I know this isn't a good thing but I will try to make big changes in the future. If you search the forum you will find other people talking about this.

I think I found the reason why I was getting this exception. In my mapping file, I had this:



This has been working fine for quite some time. But in reading some posts on the forum, I thought I would try this:



That seems to have fixed the problem. I'm able to open a new session for each of my winforms and have each form isolated from each other. (i.e. Save on Form B doesn't try to save changes made to Form A). There might be some kinks to work out, but it seems to be working. No exceptions and data actually makes it to the database!

Still have no idea why it has been working for so long without the "unsaved-value" config setting, but ohhhh well.