Concatenate columns using derived column in ssis

What I am trying to achieve is Column 5:

Column 1 Columns 2 Column 3 Column 4  Column 5
A        B                  D         A|B|D

I used a derived column:

(DT_STR,50,1252)([A] + "|" + [B] + "|" + [C] + "|" + [D])

But I ended with:

Column 1 Columns 2 Column 3 Column 4  Column 5
A        B                  D         A|B||D

I'm struggling to find the right solution.