在 ASP.NET Core API 中使用 DTO 和 AutoMapper 时的 HttpPut

Question

In my API project I have Course model such:

 public class Course
 {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int CourseId { get; set; }
        public string CourseName { get; set; }
        [ForeignKey("Department")]
        public int DepartmentId { get; set; }
        public Department Department { get; set; }
        public ICollection<CourseEnrollment> CourseEnrollments { get; set; }
        public ICollection<CourseAssignment> CourseAssignments { get; set; }
 }

I want to applied the DTO and AutoMapper concepts to my update course action using HttpPut , so I created a CourseUpdateDto DTO such:

public class CourseUpdateDTO
{
     [Required]
     public int CourseId { get; set; }
     [Required, MaxLength(100)]
     public string CourseName { get; set; }
     [Required]
     public int DepartmentID { get; set; }
}

This is my AutoMapper configuration:

 CreateMap<CourseUpdateDTO, Course>()
          .ForMember(dest => dest.CourseId,
                     opts => opts.MapFrom(src => src.CourseId))
          .ForMember(dest => dest.CourseName,
                     opts => opts.MapFrom(src => src.CourseName))
          .ForMember(dest => dest.DepartmentId,
                     opts => opts.MapFrom(src => src.DepartmentID));

And finally this is my trial to update course:

[HttpPut("{id:int}")]
public ActionResult PutCourse(int id, [FromBody] CourseUpdateDTO courseDto)
{
       if (courseDto is null)
       {
           return BadRequest();
       }

       var entity = new Course
       {
            CourseId = id,
            CourseName = courseDto.CourseName,
            DepartmentId = courseDto.DepartmentID
       };

       _mapper.Map(courseDto, entity);

       try
       {
           _unitOfWork.SaveChangesAsync();
       }
       catch (DbUpdateConcurrencyException)
       {
           ModelState.AddModelError(nameof(PutCourse), "unable to save changes");
           return StatusCode(500, ModelState);
       }

       return NoContent();
}

When I tested this action using Postman, it returned status of 204 But the course has not changed. Am I wrong anywhere? Im new to this concept so hope someone configure that out to me.

Answer 1

You didn't call the update method before saving. After mapping call update method and after call SaveChangesAsync();

Answer 2

First of all, you need to get an exact record from your database (here I mean get it from DbContext ), then map incoming data to your entity.

To make it works, you have to apply some changes like below:

var entity=_context.Cources.SingleOrDefault(x=>x.Id=id);

// check if it is not null 

_mapper.Map(courseDto, entity);
 _context.Entity(entity).Status = Status.Modified;
_context.SaveChangesAsync();

Answer 3

After got some suggestions from people in this post. I've changed the original action

[HttpPut("{id:int}")]
public ActionResult PutCourse(int id, [FromBody] CourseUpdateDTO courseDto)
{
       if (courseDto is null)
       {
           return BadRequest();
       }

       var entity = new Course
       {
            CourseId = id,
            CourseName = courseDto.CourseName,
            DepartmentId = courseDto.DepartmentID
       };

       _mapper.Map(courseDto, entity);

       try
       {
           _unitOfWork.SaveChangesAsync();
       }
       catch (DbUpdateConcurrencyException)
       {
           ModelState.AddModelError(nameof(PutCourse), "unable to save changes");
           return StatusCode(500, ModelState);
       }

       return NoContent();
}

to this

[HttpPut("{id:int}")]
        public async Task<ActionResult> PutCourse(int id, [FromBody] CourseUpdateDTO courseDto)
        {
            if (courseDto is null)
            {
                return BadRequest();
            }

            var entity = _unitOfWork.CourseService.Get(id);
            if (entity is null)
            {
                return NotFound();
            }

            _mapper.Map(courseDto, entity);
            try
            {
                _unitOfWork.SaveChangesAsync();
            }
            catch (DbUpdateConcurrencyException)
            {
                ModelState.AddModelError(nameof(PutCourse), "unable to save changes");
                return StatusCode(500, ModelState);
            }

            return NoContent();
        }

However, it still doesn't work. But I realized the problem might be in the _unitOfWork.SaveChangesAsync(); that used async/await . but I didn't define the function as async. So I changed the function to async and add await await _unitOfWork.SaveChangesAsync(); . Finally, it worked! Very thanks for your warm support!