Graphical mapping not workig for IF else

Hi,

I have two fields A and B in source side and i have to map it to C in the destination side depending on the condition.

The condition is If there is any value in B then map B to C otherwise map A to C.

Here A is mandatory B is optional and C is mandatory fields.

I mapped it like: if B exists then --> pass this to IF else --> if true map B ; in else condition A to C.

My problem is if I have any value in B it is working fine. But if I don’t have anything in B then C should get value from A. But this is not happening.