.Net Core API & 具有多对多关系映射的 Automapper

Question

实体 User-UsersProjects-Project 之间存在多对多关系。

我想要获取分配给指定（按 projectID）项目的用户的映射列表，其中包含有关通常分配给用户的项目数量的信息，而不是每个项目。

请看我的代码

控制器

        [HttpGet("{projectId}/users-assigned")]
        [Description("Get list of users assigned to a specified project.")]
        public async Task<ActionResult> GetProjectUsers(int projectId)
        {
            if (!ProjectExistById(projectId)) return NotFound("Project doesn't exist");
            var project = await _context.Projects.Include(x => x.UserProjects).ThenInclude(z => z.User).SingleOrDefaultAsync(x => x.ProjectId == projectId);
            var users = project.UserProjects.Select(x => x.User).ToList();

            var usersDto = _mapper.Map<ICollection<UserForProjectDTO>>(users);
            return Ok(usersDto);
        }

实体

public class AppUser : IdentityUser<int>
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public ICollection<AppUserProject> UserProjects { get; set; }
    }


public class Project
    {
        [Key]
        public int ProjectId { get; set; }
        public string Number { get; set; }
        public string Name { get; set; }
        public ICollection<AppUserProject> UserProjects { get; set; }

    }

public class AppUserProject
    {
        [Key]
        public int UserId { get; set; }
        public AppUser User { get; set; }


        [Key]
        public int ProjectId { get; set; }
        public Project Project { get; set; }
    }

DTO

    public class UserForProjectDTO
    {
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public int ProjectsCount { get; set; }

    }

AutoMapper 配置文件

    CreateMap<AppUser, UserForProjectDTO>();
    CreateMap<AppUserProject, UserForProjectDTO>();

当前结果/api/Projects/11/users-assigned

[
    {
        "id": 4,
        "firstName": "Robert",
        "lastName": "Lewandowski",
        "projectsCount": 0
    },
    {
        "id": 6,
        "firstName": "Ernest",
        "lastName": "Giovannni",
        "projectsCount": 0
    },
    {
        "id": 7,
        "firstName": "Mark",
        "lastName": "Looser",
        "projectsCount": 0
    },
    {
        "id": 8,
        "firstName": "Frank",
        "lastName": "Lampard",
        "projectsCount": 0
    },
    {
        "id": 9,
        "firstName": "Mark",
        "lastName": "Ruffalo",
        "projectsCount": 0
    }
]

预期结果

[
    {
        "id": 4,
        "firstName": "Robert",
        "lastName": "Lewandowski",
        "projectsCount": 4
    },
    {
        "id": 6,
        "firstName": "Ernest",
        "lastName": "Giovannni",
        "projectsCount": 2
    },
    {
        "id": 7,
        "firstName": "Mark",
        "lastName": "Looser",
        "projectsCount": 2
    },
    {
        "id": 8,
        "firstName": "Frank",
        "lastName": "Lampard",
        "projectsCount": 1
    },
    {
        "id": 9,
        "firstName": "Mark",
        "lastName": "Ruffalo",
        "projectsCount": 1
    }
]

我的数据库

现在我总是得到 0 或 1（取决于我如何映射，但它仍然不是我所期望的）。

问题是因为我想通过项目 ID 获取具有项目数量的用户列表，而不是针对所有项目。这是我第一次遇到这种问题。任何提示都会有用。

Answer 1

我认为您在这里不需要 AutoMapper。一次性查询，无需第三方库，可自行投影所需属性

var users = 
    from p in context.Projects
    where p.ProjectId == projectId
    from up in p.UserProjects
    select new UserForProjectDTO
    {
        Id = up.UserId,
        FirstName = up.User.FirstName,
        LastName = up.User.LastName,
        ProjectsCount = up.User.UserProjects.Count()
    };

作为一个好处，您可以更快地查询，只加载需要的字段而不会产生开销。

.Net Core API & 具有多对多关系映射的 Automapper

.Net Core API & Automapper with many to many relationship mapping

.net

c#

linq

many-to-many

automapper