Angular 4 setting selected option in Dropdown

Question

several questions about this and diffrent answeres. But none of them realy answeres the question. So again:

Setting default of a Dropdown select by value isnt workin

Answer 1

If you want to select a value based on true / false use

[selected]="opt.selected == true"

 {{opt.selected+opt.value}}

checkit out

Angular 2 - Setting selected value on dropdown list