添加新行时无法添加或更新子行

Question

我已经看到了这个答案，并且正在使用它所建议的解决方案，但仍然得到相同的错误。

我有一个对用户表有外键约束的代理表，这是代理表：

CREATE TABLE agency (
    AgencyId                BIGINT          NOT NULL    AUTO_INCREMENT,
    UserId                  BIGINT          NOT NULL,
    AgencyName              VARCHAR(150)    NOT NULL,

    CONSTRAINT PK_Agency PRIMARY KEY(AgencyId),
    CONSTRAINT FK_Agency_User FOREIGN KEY (UserId) REFERENCES user (UserId) ON DELETE RESTRICT ON UPDATE RESTRICT
);

这是我的代理实体：

[Table("agency")]
public class Agency
{
    public long AgencyId { get; set; }

    [Required]
    public long UserId { get; set; }

    [ForeignKey("UserId")]
    public User User { get; set; } // <-- user Entity

    [Required]
    [StringLength(GlobalConstants.MaxLengthForLongName)]
    public string AgencyName { get; set; }
}

现在，我想为现有用户添加一个新代理：

public void AddOrUpdateAsAdminUser(Agency agency)
{
    if (agency.UserContact.UserId <= 0)
    {
        throw new Exception($"User: {agency.User.Email} does not exists");
    }

    if (agency.AgencyId > 0)
    {
        // update existing agency
        _context.Agency.Attach(agency);
        _context.Entry(agency).State = EntityState.Modified;
        _context.Entry(agency).Property(x => x.UserId).IsModified = false;
        _context.Entry(agency.User).State = EntityState.Detached; // <-- don't update User
    }
    else
    {
         // add new agency: exception is thrown here
        _context.Agency.Add(agency);
        _context.Entry(agency.User).State = EntityState.Detached; // <-- Don't update User
    }

    _context.SaveChanges();
}

<代码>\u上下文。SaveChanges（） 行引发以下异常：

"无法添加或更新子行：外键约束失败（\"dbName\".\"agent\"， CONSTRAINT\"FK_Agency_User\"FOREIGN KEY（\"UserId\"）REFERENCES\"user\"（\"UserId\"））"

系统异常{MySql.Data.MySqlClient.MySqlException}

Answer 1

问题在于我的映射逻辑，当将代理视图模型映射到代理时，我只是将用户视图模型映射到用户。。。这意味着当我想保存代理时，UserId是0（未映射）。

[Table("agency")]
public class Agency
{
    public long AgencyId { get; set; }

    [Required]
    public long UserId { get; set; }  // <-- I was NOT mapping UserId

    [ForeignKey("UserId")]
    public User User { get; set; } // <-- I was mapping User

    [Required]
    [StringLength(GlobalConstants.MaxLengthForLongName)]
    public string AgencyName { get; set; }
}

Answer 2

您会收到此错误，因为您正在尝试向代理添加/更新一行，该行没有基于当前存储在表1中的值的UserID字段的有效值。