LogicLib with empty string

i am trying to replace

StrCmp $0 "" This That

with an if function. I tried using "" and empty variables and definitions. no success. any solution?

I'm not sure what you mean when you say function, but the logic lib is good for stuff like this

!include LogicLib.nsh
${If} $0 == ""
    MessageBox mb_ok "foo"
    ${Else}
    MessageBox mb_ok "bar"
    ${EndIf}