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[英]ASP.NET Entity Framework LINQ to Entities does not recognize the method 'System.DateTime ToDateTime(System.String)
[英]Asp.Net Core / Entity Framework Core - System.Linq.Enumerable+SelectEnumerableIterator`2[MyClass,System.String]
我正在尝试返回我的 3 级深度相关数据的 json 数组,这里的问题是我得到的结果具有正确的属性名称但值内容不明确,我未能找到类似的案例来解决它。 从返回的值消息看来,我正在返回一个可查询的而不是最终结果,并且我需要对其进行迭代,我尝试了几种方法来实现它,但未能找到正确的方法。
json 结果:
[
{
"registeredYear": "System.Linq.Enumerable+SelectEnumerableIterator`2[MyPath.Groups.GroupYear,System.String]"
}
]
api 端点
public async Task<ActionResult<IEnumerable<UserGroup>>> GetUserGroupYears(string email, string groupName)
{
var groupYears = await _repo.GetUserGroupYears(email, groupName);
var mappedEntities = _mapper.Map<GroupYearsListDto[]>(groupYears);
return Ok(mappedEntities);
}
存储库方法
public async Task<IEnumerable<UserGroup>> GetUserGroupYears(string email, string groupName)
{
var userGroupYears = _context.UserGroups
.Include(uo => uo.Group.GroupYears)
.ThenInclude( oy => oy.Year)
.Where(uo => uo.Group.Name == groupName && uo.Email == email );
return await userGoupYears.ToArrayAsync();
}
使用的类:
public class UserGroup
{
public string Email { get; set; }
public string UserId { get; set; }
public virtual User User { get; set; }
public string GroupId { get; set; }
public virtual Group Group { get; set; }
}
public class Group
{
public string Name { get; set; }
public virtual ICollection<UserGroup> Users { get; set; }
public virtual ICollection<GroupYear> GroupYears { get; }
}
public class GroupYear {
public string GroupId { get; set; }
public virtual Group Group { get; set; }
public string YearId { get; set; }
public virtual Year Year { get; set; }
public string RegisteredYear { get; set; }
}
数据传输 object 和映射:
public class GroupYearsListDto
{
public string RegisteredYear { get; set; }
}
public CoreMappingProfiles()
{
CreateMap<UserGroup, GroupYearsListDto>()
.ForMember(
dest => dest.RegisteredYear,
opt => opt.MapFrom(src => src.Group.GroupYears.Select(x => x.RegisteredYear))
);
}
更新:附加调试器显示存储库方法正在返回一个包含正确值的 IQueryable,并且 controller 方法在映射时出错。 所以我认为以下行是导致错误结果的原因:
var mappedEntities = _mapper.Map<GroupYearsListDto[]>(GroupYears);
你得到这个 JSON 结果:
[
{
"registeredYear": "System.Linq.Enumerable+SelectEnumerableIterator`2[MyPath.Groups.GroupYear,System.String]"
}
]
因为您正在将IEnumerable<string>
映射到string
,正如我在评论中提到的那样。 所以基本上你得到的是相同的:
CreateMap<UserGroup, GroupYearsListDto>()
.ForMember(
dest => dest.RegisteredYear,
opt => opt.MapFrom(src =>
{
IEnumerable<string> registeredYears = src.Group.GroupYears.Select(x => x.RegisteredYear);
return registeredYears.ToString();
})
);
而registeredYears.ToString()
是"System.Linq.Enumerable+SelectEnumerableIterator`2[MyPath.Groups.GroupYear,System.String]"
。
我想你会:
src.Group.GroupYears.Select(x => x.RegisteredYear).Single()
string.Join(", ", src.Group.GroupYears.Select(x => x.RegisteredYear))
您有很多选择,但您实际上需要向该属性返回一个string
,否则您只会获得IEnumerable<string>
的ToString()
版本。
更新:
根据您在下面的评论,您可以尝试以下操作:
存储库:
public IQueryable<GroupYear> GetGroupYears(string email, string groupName)
{
return _context
.UserGroups
.Where(x => x.Group.Name == groupName && x.Email == email)
.SelectMany(x => x.Group.GroupYears);
}
Controller:
public async Task<ActionResult<GroupYearsListDto[]>> GetGroupYears(string email, string groupName)
{
var groupYears = _repo.GetGroupYears(email, groupName);
var projection = _mapper.ProjectTo<GroupYearsListDto>(groupYears)
var mappedEntities = await projection.ToArrayAsync();
return Ok(mappedEntities);
}
轮廓:
CreateMap<GroupYears, GroupYearsListDto>();
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