为什么 EF 核心告诉我 'specified member is unmapped'？

Question

我想通过使用投影查询（通过 Select）按名称和 return 新 DTO 过滤用户：

var result = context.Users
    .Where(user => user.FullName == search)
    .Select(u => new UserPagingViewModel
    {
        Id = u.Id,
        IsSearchable = u.IsSearchable,
        FirstName = u.FirstName,
        LastName = u.LastName,
        FullName = u.FullName,
        Photo200 = u.Photo200,
        City = u.City,
        About = u.About,
        Skills = u.UserSkills.Select(us => us.Skill.Name),
        IsTeamMember = u.UserTeams.Any(ut => ut.UserAction == UserActionEnum.JoinedTeam)
    })
    .ToList();

用户class:

public class User : IHasId
{
    public long Id { get; set; }
    public string FirstName { get; set; }
    public string SecondName { get; set; }
    public string LastName { get; set; }
    public string City { get; set; }
    public string About { get; set; }
    public string Telegram { get; set; }
    public string Email { get; set; }
    public string Mobile { get; set; }
    public string FullName => FirstName + " " + SecondName + " " + LastName;
    public string Photo100 { get; set; }
    public string Photo200 { get; set; }
    public bool IsModerator { get; set; }
    public List<UserTeam> UserTeams { get; set; }
    public List<UserSkill> UserSkills { get; set; }

    [NotMapped]
    public List<Team> TeamsToRecruit { get; set; }
    [NotMapped]
    public bool AnyTeamOwner { get; set; }
}

数据库是 PostgreSql。数据提供者 PostgreSQL/Npgsql provider for Entity Framework Core

但是当我尝试执行此请求时，出现异常并显示以下消息：

The LINQ expression 'DbSet<User>() .Where(u => user.FullName == search)' could not be translated. Additional information: Translation of member 'FullName' on entity type 'User' failed. This commonly occurs when the specified member is unmapped. Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038 for more information.

我不想使用客户评价。例如，如果我比较 FirstName 属性一切正常。

请帮我想办法解决这个问题。

Answer 1

您在三个地方有全名。由于您没有全名列（或计算列），因此不能在 dbcontext 查询中使用它。它将生成如下所示的 sql。

SELECT FULLNAME,... FROM USERS WHERE FULLNAME = N"some value".

这就是您收到错误的原因。

您需要从 dbcontext 查询中删除所有 FullName 并像下面那样执行 where 过滤器。

var result = context.Users
    .Where(x => (x.FirstName + " " + x.SecondName + " " + x.LastName) == search)
    .Select(u => new UserPagingViewModel
    {
        Id = u.Id,
        IsSearchable = u.IsSearchable,
        FirstName = u.FirstName,
        LastName = u.LastName,
        //FullName = u.FullName,
        Photo200 = u.Photo200,
        City = u.City,
        About = u.About,
        Skills = u.UserSkills.Select(us => us.Skill.Name),
        IsTeamMember = u.UserTeams.Any(ut => ut.UserAction == UserActionEnum.JoinedTeam)
    })
    .ToList();

你会像下面这样

FROM [Users] AS [t]
WHERE ([t].[FirstName] + N' ' + [t].[SecondName] + N' ' + [t].[LastName]) = N'some value'

然后从用户对象中删除 FullName。

public class User : IHasId
{
    public long Id { get; set; }
    public string FirstName { get; set; }
    public string SecondName { get; set; }
    public string LastName { get; set; }
    public string City { get; set; }
    public string About { get; set; }
    public string Telegram { get; set; }
    public string Email { get; set; }
    public string Mobile { get; set; }
    // public string FullName => FirstName + " " + SecondName + " " + LastName;
    public string Photo100 { get; set; }
    public string Photo200 { get; set; }
    public bool IsModerator { get; set; }
    public List<UserTeam> UserTeams { get; set; }
    public List<UserSkill> UserSkills { get; set; }

    [NotMapped]
    public List<Team> TeamsToRecruit { get; set; }
    [NotMapped]
    public bool AnyTeamOwner { get; set; }
}

将全名添加到 UserPagingViewModel。

public class UserPagingViewModel{
    ...
    public string FirstName { get; set; }
    public string SecondName { get; set; }
    public string LastName { get; set; }
    public string FullName => $"{FirstName} {SecondName} {LastName}";
}

如果您希望全名作为用户对象的一部分，则添加为未映射或使用 HasComputedColumnSql

为什么 EF 核心告诉我 'specified member is unmapped'？

Why EF core tell me 'specified member is unmapped'?

.net

c#

linq-to-entities

entity-framework-core

asp.net-core