....	
NewFLdlg dlg;
/* 
dlg is my file dialog and apart from some bits and bolts 
it has a button ofs (open file selector)
and an editstring path (to take ... you guessed it ... my file path)
*/ 
String fsp = "nixx"; // just a String I added to test if the lambda can read 'outside'
dlg.button.WhenPush = [=]
{
	FileSelector fs; 
	fs.AllFilesType().Multi(true);
	if(fs.ExecuteOpen("Dummy Demo"))
		PromptOK("\1"+~fs);
	else
		PrompOK(fsp); // works so far...
/* BUT

		fsp = ~fs; // is not working since fsp is now a const 
		//error: passing 'const Upp::String' as 'this' argument discards qualifiers [-fpermissive]
		PromptOK(AsString(~dlg.path)); // error: use of deleted function 'NewFLdlg::NewFLdlg(NewFLdlg&)'
Not even mentioning
		dlg.path = ~fs; // what I'm really after 

*/
};
.....

dlg.button.WhenPush = [&]

dlg.button.WhenPush = [=]

class NewFLdlg final : public WithMyAweasomeLayout<TopWindow>
{
public:
    NewFLdlg() {
        // This callback logic should be implemented here... (Not outside the class - I am not surre why we have public inheritance here)
        button.WhenAction = [=] {
            // this->fsp should be available here.
        }
    }    

    String GetFsp() const { return fsp; }

private:
    String fsp;
};

// Then in the main code
NewFLdlg dlg;
if (dlg.Execute() == IDOK) // Check if user close dialog with success - you need "OK" button for such operations...
{
    String fsp = dlg.GetFsp(); // Here you should have valid fsp with nice object related design.
}