Angular 2 - 来自组件的简单HTTP GET不工作

I have an Angular 2 app that has a simple component (see below). It makes a simple GET call to a Web Api endpoint. I can call the end point using postman but when this component tries to it fails. The call is never made and no errors are output. What have I done wrong? I've followed this pattern before.I have an Angular 2 app that has a simple compo