Can I use string function inside controller or not on ASP.NET mvc5 when routing ?

See more:

MVC5

entity-framework

C#6.0

PROBLEM

can I use string function inside controller and replace action or not on asp.net mvc5 ?

on mvc when link to any webapplication i use default route
controller/action
can i use function return string as function ShowText() after controller
meaning controller/ShowText or must use ActionResult ?
and when route to link Employee/ShowText
are this route will work ?

What I have tried:

controller
public string ShowText()
{
string show = "welcom ";
return show ;
}