how to have multiple type for generics in child class

Question

I have a BaseController

public abstract class BaseController<T> : ApiController 
{

    protected APIResponseTO<T> _reponse;

    protected IHttpActionResult CreateResponse(HttpStatusCode httpStatus, T data)
    {
        _reponse = new APIResponseTO<T>()
        {
            HttpStatus = httpStatus,
            Data = data
        };
        return Ok(_reponse);
    }
}

Now I want that any Class which inherits this class can define multiple types for T as

 public class CustomerController : BaseController<T>
 {

    public IHttpActionResult Get()
    {

        var customers = _customerService.GetCustomers();
        //call Parent Class CreateResponse() to create IHttpActionResult object
        //here customers is IEnumerable<Customer>
        return CreateResponse(HttpStatusCode.Created, customers)
    }

    public IHttpActionResult Post([FromBody]Customer customer)
    {
        var custId= _customerService.AddCustomers();
        //call Parent Class CreateResponse() to create IHttpActionResult object
        //here customer is integer(Single Object)
        return CreateResponse(HttpStatusCode.Created, custId)
    }
}

What my requirement is either I can define somehow at the class level

public class CustomerController : BaseController<T> where T : Customer, IEnumerable<Customer>, int
 {
 }

or at Method Level

 public IHttpActionResult Post<T>([FromBody]Customer customer)
  where T : int
    {
        var custId= _customerService.AddCustomers();
        //call Parent Class CreateResponse() to create IHttpActionResult object
        //here customer is integer(Single Object)
        return CreateResponse(HttpStatusCode.Created, custId)
    }

Thanks.

Answer 1

I am not entirely sure I understood exactly what you need, but I think I have an idea.
I think you should not use a generic class but instead use a generic method:

public class CustomerController : BaseController
{

    public IHttpActionResult Get()
    {

        var customers = new List<object>();
        return CreateResponse<List<object>>(HttpStatusCode.Created, customers);
    }

    public IHttpActionResult Post([FromBody]Customer customer)
    {
        int custId = 17;
        return CreateResponse<int>(HttpStatusCode.Created, custId);
    }
}

public abstract class BaseController : ApiController
{

    protected IHttpActionResult CreateResponse<TData>(HttpStatusCode httpStatus, TData data)
    {
        // Problem here is that BaseController is not a generic class anymore, so you can't store your responses but then again, why would you want to store them in a variable?
        var reponse = new APIResponseTO<TData>()
        {
            HttpStatus = httpStatus,
            Data = data
        };

        return Ok(reponse);
    }
}

Hope this helps.