static object reference issue using Query in Controller

I am a newbie in CQRS / MediatR, so tried to figure out myself with the demo. I implemented Query and Handler in a class, those classes will be read in Controller. However, I have struggled with the error in Controller, so tried to way#1 and way#2 but didn’t get resolved. Can you let me know what I made mistake here?

My dev environment is .NET Core 3.1 and MedatR version 9

Query/ Handler

using Application.DTO;
using AutoMapper;
using MediatR;
using Microsoft.EntityFrameworkCore;
using Persistence;
using Persistence.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Application.Handlers
{
    public class OrgList
    {

        public class Query : IRequest<List<OrgDTO>>
        {
         
        }

        public class Handler : IRequestHandler<Query, List<OrgDTO>>
        {
            private readonly BlogContext _context;
            private readonly IMapper _mapper;

            public Handler(BlogContext context, IMapper mapper)
            {
                _context = context;
                _mapper = mapper;
            }

            public async Task<List<OrgDTO>> Handle(Query request, CancellationToken cancellationToken)
            {

                var organizations = await _context.Organizations
                                                        .Where(o => o.activation == true)
                                                        .Include(o => o.Employees)
                                                        .ToListAsync(); 
                List<OrgDTO> result = _mapper.Map<List<Organization>, List<OrgDTO>>(organizations);
                return result;
            }
        }
    }
}

Controller__way#1

...
[HttpGet]
public async Task<ActionResult<List<OrgDTO>>> GetAllOrg()
{
   return await Mediator.Send(new OrgList.Query); //<--- Error occurs here.
}
...

Error Message_way#1

Severity	Code	Description	Project	File	Line	Suppression State
Error	CS1526	A new expression requires an argument list or (), [], or {} after type

Controller_way#2

 [HttpGet]
public async Task<ActionResult<List<OrgDTO>>> GetAllOrg()
{
  return await Mediator.Send(new OrgList.Query { }); //<--- Error occurs here.
// return await Mediator.Send(new OrgList.Query()); //<--- same result
}

Error Message_way#2

Severity	Code	Description	Project	File	Line	Suppression State
Error	CS0120	An object reference is required for the non-static field, method, or property 'Mediator.Send<List<OrgDTO>>(IRequest<List<OrgDTO>>, CancellationToken'

[iyamus]

Well, I found a way to create a constructor with IMediator DI that works fine. But is this a normal way to use a constructor in the Controller? Or is there another way, such as calling Mediator directly in the Controller as I tried before?

    public class OrgController : ControllerBase
    {
        private readonly IMediator _mediator;

        public OrgController(IServices services, IMediator mediator)
        {
            _mediator = mediator;
        }

        [HttpGet]
        public async Task<ActionResult<List<OrgDTO>>> GetAllOrg()
        {
            return await _mediator.Send(new OrgList.Query());
        }

[iyamus]

@djeikyb @neozhu Thank you for your comments. It’s helpful. Have a great day!