Creación de pago .NET

CrearPago.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using AdminLTE.Data;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using MercadoPago;
using MercadoPago.Resources;
using MercadoPago.DataStructures.Payment;
using MercadoPago.Common;
using Microsoft.AspNetCore.Authorization;

namespace AdminLTE.APIs
{
    [Route("api/[controller]")]
    [ApiController]
    [AllowAnonymous]
    public class MPController : ControllerBase
    {


        private readonly ApplicationDbContext db;

        public MPController(ApplicationDbContext _context)
        {

            db = _context;
        }

        // GET: api/MP
        [HttpGet("",Name ="TryPayment")]
        public async Task<IActionResult> TryPayment()
        {
            //For Web-checkout:
            MercadoPago.SDK.SetAccessToken("TEST-4123207277....-350922726");

            Payment payment = new Payment()
            {
                TransactionAmount = float.Parse("100.0"),
                Token = "2b00e16a09...a348399db4",
                Description = "Ergonomic Silk Shirt",
                PaymentMethodId = "visa",
                Installments = 1,
                Payer = new Payer()
                {
                    Email = "[email protected]"
                }
            };

            payment.Save();  //En esta linea se crashea

            var status = payment.Status;



            return null;
        }

        
    }
}