Today I want to write a few words on usage of PXLongOperation. 

Compare two following scenarios:

Base.Save.Press();
            try
            {
                PXLongOperation.StartOperation(Base,  ()=>
                {
                    //Some other code
                    Base.Save.Press();

with this:

Base.Save.Press();
 
var doc = Base.Document.Current;
var orderType = doc.OrderType;
var orderNbr = doc.OrderNbr;
 
try
{
    PXLongOperation.StartOperation(Base,  ()=>
    {
        var grp = PXGraph.CreateInstance<SOOrderEntry>();
        grp.Document.Current = grp.Document.Search<SOOrder.orderNbr>(orderNbr, orderType);
 
        grp.Save.Press();
    });

and tell me what will be the difference in execution of those two types of code?

I spent pretty big amount of time wondering why in Acumatica source code I often seen scenario #2. Reason why I was puzzled is that I don't like to create instance of something, if I can use some variable that exists already. 

And finally I've discovered reason on why scenario #2 is preferable. After our team spent some time on digging on the following use case scenario. We've used scenario #1 and QA gave us very interesting bug: some buttons on UI level got disabled after execution of #1 scenario. The only way to enable them in scenario #1 was just to call refresh of the page:

throw new PXRedirectRequiredException(Base, false, "Sales Orders");

which is not the worst in life of end user, but definetly not the most convenient. How to avoid total refresh of the screen? Use scenario #2. 

Another important aspec of scenario #2 is usage of variables. Take note, that inside of PXLongOperation I don't use Base.Document.Current.OrderType. Instead I use local variables doc, orderType and orderNbr which is then used at async thread. 

Summary

Starting from today I plan to use #2 whenever I will deal with multithreading scenarions. Otherwise some UI problems will become some kind of guarantee.