today I want to describe how analogue to Required works in Acumatica Framework.
For example, in the past ( before 2019 R1 ) you may read something from Acumatica with help of Required:
var contact = PXSelect<Contact, Where<Contact.displayName, IsNotNull, And<Contact.displayName,
Contains<Required<Contact.displayName>>>>>.SelectWindowed(graph, startIdx, 1, ' ').First();
Now, you can use @P.AsString, as shown on code sample below:
var contact = SelectFrom<Contact>.Where<Contact.displayName.IsNotNull.And<Contact.displayName.
Contains<@P.AsString>>>.View.SelectWindowed(graph, startIdx, 1, ' ').First();
Also take a note, that FBQL looks a bit simpler then BQL which has plenty of <<<>>>>