为什么 Visual Studio 会使用所有异步方法自动创建 ApiController？ 如何创建带有同步方法的 ApiController？

Question

我使用 Entity Framework 使用Visual Studio 提供的功能创建了一个名为StudentsController.cs的 asp.net 核心 webapi 控制器，该功能是带有操作的 API 控制器。 它实现了所有控制器方法，返回类型为async Task<ActionResult<>> ，这是异步方法实现，由 Visual Studio 自动生成

问题是为什么它自己创建所有异步方法，以及如何使用 Visual Studio 的相同自动生成功能同步创建所有方法？

控制器的异步示例

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Students.Models;

namespace Students.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class StudentsController : ControllerBase
    {
        private readonly StudentContext _context;

        public StudentsController(StudentContext context)
        {
            _context = context;
        }

        // GET: api/Students
        [HttpGet]
        public async Task<ActionResult<IEnumerable<Student>>> GetStudents()
        {
            return await _context.Students.Include(d => d.Department).ToListAsync();
        }

        // GET: api/Students/5
        [HttpGet("{id}")]
        public async Task<ActionResult<Student>> GetStudent(int id)
        {
            var student = await _context.Students.Include(d => d.Department).FirstOrDefaultAsync(i => i.SId == id);

            if (student == null)
            {
                return NotFound();
            }

            return student;
        }

        // PUT: api/Students/5
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for
        // more details see https://aka.ms/RazorPagesCRUD.
        [HttpPut("{id}")]
        public async Task<IActionResult> PutStudent(int id, Student student)
        {
            if (id != student.SId)
            {
                return BadRequest();
            }
            _context.Departments.Update(student.Department);
            await _context.SaveChangesAsync();
            _context.Entry(student).State = EntityState.Modified;

            try
            {
                await _context.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!StudentExists(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

            return Ok();
        }
        //[HttpPut]
        //public async Task<IActionResult> PutStudent(Student student)
        //{

        //    _context.Departments.Update(student.Department);
        //    await _context.SaveChangesAsync();
        //    _context.Entry(student).State = EntityState.Modified;

        //    try
        //    {
        //        await _context.SaveChangesAsync();
        //    }
        //    catch (DbUpdateConcurrencyException)
        //    {
        //        if (!StudentExists(student.SId))
        //        {
        //            return NotFound();
        //        }
        //        else
        //        {
        //            throw;
        //        }
        //    }

        //    return Ok();
        //}

        // POST: api/Students
        // To protect from overposting attacks, please enable the specific properties you want to bind to, for
        // more details see https://aka.ms/RazorPagesCRUD.
        [HttpPost]
        public async Task<ActionResult<Student>> PostStudent(Student student)
        {
            _context.Students.Add(student);
            await _context.SaveChangesAsync();

            return CreatedAtAction("GetStudent", new { id = student.SId }, student);
        }


        [HttpPost]
        [Route("StudentList")]
        public async Task<ActionResult<Student>> PostStudentList([FromBody] List<Student> student)
        {
            try
            {
                foreach (Student s in student)
                {
                    _context.Students.Add(s);
                }
                _context.SaveChanges();
                return CreatedAtAction("GetStudents", student, _context.Students.Include(d => d.Department));
            }
            catch(Exception ex)
            {
                return BadRequest();
            }
        }

        // DELETE: api/Students/5
        [HttpDelete("{id}")]
        public async Task<ActionResult<Student>> DeleteStudent(int id)
        {
            var student = await _context.Students.FindAsync(id);
            if (student == null)
            {
                return NotFound();
            }

            _context.Students.Remove(student);
            await _context.SaveChangesAsync();

            return student;
        }

        private bool StudentExists(int id)
        {
            return _context.Students.Any(e => e.SId == id);
        }
    }
}

控制器同步示例

using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using CourseCRUD.Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;

namespace CourseCRUD.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class SubjectController : Controller
    {
        private readonly CourseContext _context;

        public SubjectController(CourseContext context)
        {
            _context = context;
        }

        [HttpGet]
        // GET:api/subject
        public IActionResult GetSubjects()
        {
            try
            {
                var subjects = _context.subjects.ToList();
                return Ok(subjects);
            }
            catch
            {
                return BadRequest();
            }
        }
        [HttpPost]
        public IActionResult AddSubject([FromBody]Subject subject)
        {

            try
            {
                _context.subjects.Add(subject);
                _context.SaveChanges();
                return CreatedAtAction("GetSubjets", subject);
            }
            catch
            {
                return BadRequest();
            }
        }
        [HttpGet("{id}")]
      public IActionResult GetSuject(int id)
        {
            try
            {
                var subject = _context.subjects.Find(id);
                return Ok(subject);
            }
            catch
            {
                return BadRequest();
            }
        }

        [HttpPut("id")]

        [HttpPut("{id}")]
        public IActionResult UpdateSubject(int id, Subject subject)
        {
            if (id != subject.SubjectId)
            {
                return BadRequest();
            }
            _context.Entry(subject).State = EntityState.Modified;
            try
            {
                _context.SaveChanges();
                return Ok(subject);
            }
            catch (DbUpdateConcurrencyException)
            {
                if (!SubjectDetailExist(id))
                {
                    return NotFound();
                }
                else
                {
                    throw;
                }
            }

        }

        private bool SubjectDetailExist(int id)
        {
            throw new NotImplementedException();
        }
        [HttpDelete("{id}")]
        public IActionResult DeleteSubject(int id)
        {
            var result = _context.subjects.Find(id);
            if (result == null)
            {
                return NotFound();
            }

            _context.subjects.Remove(result);

            try
            {
                _context.SaveChanges();
                return Ok(result);
            }
            catch
            {
                return BadRequest();
            }
        }

    }
}```

Answer 1

很久没有用 t4 模板做任何事情了，所以有点生疏，但你也许应该从这里开始

https://docs.microsoft.com/en-us/visualstudio/modeling/code-generation-and-t4-text-templates?view=vs-2019

您在文本文件中指定模板并使用规则来生成所需的代码。

<#@ output extension=".cs" #>
<#@ assembly name="System.Xml" #>
<#
 System.Xml.XmlDocument configurationData = ...; // Read a data file here.
#>
namespace Fabrikam.<#= configurationData.SelectSingleNode("jobName").Value #>
{
  ... // More code here.
}

根据 XML 文件中的值，生成的 .cs 文件将类似于以下内容：

namespace Fabrikam.FirstJob
{
  ... // More code here.
}

---

我不知道控制器脚手架是否使用 t4 模板，但它不会让我感到惊讶......或类似的东西。

Answer 2

async操作由脚手架模板生成，该模板位于类似于C:\\ProgramFiles\\dotnet\\sdk\\NuGetFallbackFolder\\microsoft.visualstudio.web.codegenerators.mvc\\2.0.3\\Templates路径中

您可以手动更改模板。参考https://stackoverflow.com/a/39503291/10158551