ASP Best practice to save var in ViewState

I have a var that is altered by several processes dependent on the users actions.  Is there a place where I can save this variable at the last pico second :-), just before page unloads, or after everything has finished changing.  I tried OnSaveStateComplete but it is too late.  Is there a correct event I c an use, or something?

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Jaydev RathodSr. Software EngineerCommented:
You can store in ViewState or Session variable depend on your requirement.
ViewState is available for entire page and Session for application
SamCashAuthor Commented:

Thanks for the response.

Further clarification...

ViewState["MyClass"] = MyClass;
Where may I put this one line of code so I am assured it will be its last state?

I do not want to put it everywhere on the page (Code Behind) that it might be accessed, there should be a place (Event) during the life cycle it could be put so it is after all changes are final.

I "think" it should be in Page_PreRender, it seems to work, but I cannot find anything (Google) on point, scarry.

-- side issue
I had quite an issue getting Page_PreRender to fire, found two posts
 1) this.PreRender += new System.EventHandler(this.Page_PreRender);
     private void Page_PreRender(object sender, EventArgs e){...}

2) protected override void OnPreRender(EventArgs e) {...}

in attempting to figure out what I may be doing with "override" I deleted it, and everything still worked!
3) protected void OnPreRender(EventArgs e)

Which should I use 1, 2, 3, or something else?
Is Page PreRender the best practice to add a variable to ViewState?

Kind Regards
SamCashAuthor Commented:
Update, #3 did not work, "override" is required, sorry.
I use PreRender for such things.Technically Page_PreRender is your last chance to tweak the page before it turns into HTML stream.
protected void Page_PreRender(object sender, EventArgs e)
        ViewState["MyClass"] = MyClass;

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SamCashAuthor Commented:

Thanks for sharing your experience!

Best Regards
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