为什么我不能在我的MVC控制器上声明多个方法？

I am trying to create a web API using .Net Core MVC. If I only declare one method on the controller, I can call the API using HttpClient from another application. However, if I add a second public method to the controller, the HttpClient call always returns status code 500, no matter which method I call, and I cannot find any errors coming from the server. What am I missing that will allow me to declare multiple methods from the same controller?I am trying to create a web API using .Net Core