我刚刚开始使用EF CF（来自PHP / MySQL的土地），我希望有人可以帮助我理解我在这里做错了什么。
使用许多很棒的教程，我已经创建了我的模型类，并且正在创建和更新数据库。但现在我遇到了Cascade Delete的问题。
根据我的理解，这是因为当一个实体可以通过Cascade Delete删除而不是创建孤立记录时 - 这是正确的吗？
public class jbsEntity
{
[Timestamp]
public Byte[] TimeStamp { get; set; }
//public User CreatedBy { get; set; }
//public User UpdatedBy { get; set; }
}
public class Customer : jbsEntity
{
public int Id { get; set; }
public string Salutation { get; set; }
[Required, StringLength(128)]
public string FirstName { get; set; }
[Required, StringLength(128)]
public string LastName { get; set; }
public string BillingName { get; set; }
[Required, StringLength(128)]
public string Address { get; set; }
[Required, StringLength(128)]
public string Suburb { get; set; }
[Required, StringLength(4)]
public string Postcode { get; set; }
public string BillingAddress { get; set; }
public string BillingSuburb { get; set; }
public string BillingPostcode { get; set; }
public virtual List<Contact> Contacts { get; set; }
public virtual List<Residence> Residences { get; set; }
}
public class Residence : jbsEntity
{
public int Id { get; set; }
[Required, StringLength(128)]
public string Name { get; set; }
[Required, StringLength(128)]
public string Address { get; set; }
[Required, StringLength(128)]
public string Suburb { get; set; }
[Required, StringLength(4)]
public string Postcode { get; set; }
public bool Active { get; set; }
public string AccessInstructions { get; set; }
public string ServiceFrequency { get; set; }
public string RegularServiceCost { get; set; }
[Required]
public int CustomerId { get; set; }
public virtual Customer Customer { get; set; }
public virtual List<Contact> Contacts { get; set; }
public virtual List<Pool> Pools { get; set; }
public virtual List<Job> Jobs { get; set; }
public virtual List<Image> Images { get; set; }
}
public class Pool : jbsEntity
{
public int Id { get; set; }
[Required, StringLength(128)]
public string Name { get; set; }
[Required, StringLength(128)]
public string Size { get; set; }
public string AccessInstructions { get; set; }
public string SurfcaceType { get; set; }
public bool Indoor { get; set; }
public decimal TargetPH { get; set; }
public decimal TargetIron { get; set; }
public decimal TargetCopper { get; set; }
public decimal TargetCalcium { get; set; }
public decimal TargetChlorine { get; set; }
public decimal TargetAlkaline { get; set; }
public decimal TargetStabiliser { get; set; }
[Required]
public int ResidenceId { get; set; }
public virtual Residence Residence { get; set; }
public virtual List<JobService> JobServices { get; set; }
public virtual List<Image> Images { get; set; }
}
public class Equipment : jbsEntity
{
public int Id { get; set; }
[Required, StringLength(128)]
public string Name { get; set; }
public string Description { get; set; }
public DateTime Installed { get; set; }
public DateTime WarrantyExpiration { get; set; }
public string Status { get; set; }
[Required]
public int PoolId { get; set; }
public virtual Pool Pool { get; set; }
public virtual List<Image> Images { get; set; }
}
public class Contact : jbsEntity
{
public int Id { get; set; }
public string Salutation { get; set; }
[Required, StringLength(128)]
public string FirstName { get; set; }
[Required, StringLength(128)]
public string LastName { get; set; }
public string Email { get; set; }
public string Mobile { get; set; }
public string Phone { get; set; }
}
public class Image : jbsEntity
{
public int Id { get; set; }
public string FileName { get; set; }
public string FilePath { get; set; }
public string MimeType { get; set; }
}
public class Job : jbsEntity
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public string InvoiceNumber { get; set; }
public string Comments { get; set; }
public string CompletionNotes { get; set; }
public string DpscActionRequired { get; set; }
public string WorkPerformed { get; set; }
public string NextCallInstruction { get; set; }
public bool ServiceComplete { get; set; }
public DateTime DueDate { get; set; }
public DateTime ScheduledDate { get; set; }
public DateTime CompletionDate { get; set; }
[Required]
public int ResidenceId { get; set; }
public virtual Residence Residence { get; set; }
public virtual List<JobService> JobServices { get; set; }
public virtual List<Image> Images { get; set; }
}
public class JobService : jbsEntity
{
public int Id { get; set; }
public string Name { get; set; }
public bool SkimSurface { get; set; }
public bool BrushWalls { get; set; }
public bool Vacuum { get; set; }
public bool BackwashRinse { get; set; }
public bool EmptyBaskets { get; set; }
public bool CleanElectrodes { get; set; }
public bool BalanceWater { get; set; }
public bool AddedAcid { get; set; }
public bool AddedClarifier { get; set; }
public bool SwimClearOnsite { get; set; }
public decimal PH { get; set; }
public decimal Iron { get; set; }
public decimal Copper { get; set; }
public decimal Calcium { get; set; }
public decimal Chlorine { get; set; }
public decimal Alkaline { get; set; }
public decimal Stabiliser { get; set; }
[Required]
public int JobId { get; set; }
public virtual Job Job { get; set; }
[Required]
public int PoolId { get; set; }
public virtual Pool Pool { get; set; }
public virtual List<Image> Images { get; set; }
}
public class User : jbsEntity
{
public int Id { get; set; }
[Required]
public string UserName { get; set; }
[Required]
public string FirstName { get; set; }
[Required]
public string LastName { get; set; }
[Required]
public string Password { get; set; }
[Required, Compare("Password")]
public string ComparePassword { get; set; }
}
我收到此错误：
{"Introducing FOREIGN KEY constraint 'Pool_Residence' on table 'Pools' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.\r\nCould not create constraint. See previous errors."}
我认为造成这个问题的关系是：
Customer -> Residences -> Pools
Job -> JobServices
Residence -> Jobs
Pools -> JobServices
任何人都可以帮助我理解我做错了什么以及如何解决这个问题？任何其他建议也欢迎！
提前致谢。
答案 0 :(得分：0)
实际上你没有做错任何事，但SQL Server不喜欢处理多个级联删除路径。实际上有两条从Residence到Pool的删除路径。
Residence - ＆gt; Job - ＆gt; JobService - ＆gt; Pool 在您的模型中，所有外键列都是不可为空的。因此EF尝试使用级联删除创建FK。
为了避免这个问题，使其中一个FK可以为空，并通过一个替代机制（如存储过程，触发器，通过代码）处理子实体的删除。