In reply to dave_59:
Thanks Dave .
I also observed that since if-else operates on property expression :
sequence seq_if ;
@( posedge clk0 ) a ##0 if( D ) B ;
endsequence
ap:assert property( seq_if );
// Output : Compilation Error : "property operator inside sequence definition"
[Q] So basically if-else can only be written within a property block , right ?