The FOREIGNKEY constraint in EF may cause loops or multiple cascading paths.

The FOREIGNKEY constraint in EF may cause loops or multiple cascading paths.

Ef, we need to pay attention when creating the foreign key, otherwise the title will appear.

Example: Project tables, project favorites tables, and user tables

The project table has the following fields: ProjectId, InputPersonId, etc.

The project favorites table has the following fields: ProjectId, UseId, etc.

The User table has the following fields: User ID, etc.

Project table:

 public partial class ProjectInfoMap : EntityTypeConfiguration<ProjectInfo>    {        public ProjectInfoMap()        {             this.ToTable("ProjectInfo");            this.HasKey(pr => pr.Id);            this.Property(pr => pr.Id).HasColumnName("ProjectId");            this.HasRequired(pr => pr.InputPerson)             .WithMany()             .HasForeignKey(pr => pr.InputPersonId);        }    }

Project favorites table:

 public partial class ProjectCollectMap : EntityTypeConfiguration<ProjectCollect>    {        public ProjectCollectMap()        {            this.ToTable("ProjectCollect");            this.HasKey(pc => pc.Id);            this.HasRequired(pc => pc.ProjectInfo)                .WithMany(p => p.ProjectCollects)                .HasForeignKey(pc => pc.ProjectId);            this.HasRequired(pc => pc.User)                .WithMany(u=>u.ProjectCollects)                .HasForeignKey(pc => pc.UserId);        }    }

User table:

public partial class UserMap: EntityTypeConfiguration<User>    {        public SISTUserMap()        {            this.ToTable("User");            this.HasKey(u => u.Id);            this.Property(u => u.Id).HasColumnName("UserId");        }        }

For analysis, if a user data in the User table is deleted,

It is like a sub-join deletion, that is, when you delete a user, multiple paths can be cascade to delete the project favorite table, and an error is displayed in the title.

Delete a user-> delete a project favorite table (deleting a project also deletes the project favorite table)

Delete a user-> delete a project favorite table

 

The solution is as follows:

1. delete one of the cascade deletions. The Code is as follows. We do not recommend this because such mappings are not appropriate.

 public partial class ProjectInfoMap : EntityTypeConfiguration<ProjectInfo>    {        public ProjectInfoMap()        {             this.ToTable("ProjectInfo");            this.HasKey(pr => pr.Id);            this.Property(pr => pr.Id).HasColumnName("ProjectId");            this.HasRequired(pr => pr.InputPerson)             .WithMany()             .HasForeignKey(pr => pr.InputPersonId)             .WillCascadeOnDelete(false);        }    }

 

2. Map InputPerson to the input user-project table, that is, associate the input user and Project id with another table. ProjectInfo Removal

this.HasRequired(pr => pr.InputPerson)             .WithMany()             .HasForeignKey(pr => pr.InputPersonId);

 public partial class ProjectInputPersonMap : EntityTypeConfiguration<ProjectInputPerson>    {        public ProjectInputPersonMap()        {            this.ToTable("ProjectInputPerson");            this.HasKey(pc => pc.Id);            this.HasRequired(pc => pc.ProjectInfo)                .WithOptional(p => p.InputPerson);            this.HasRequired(pc => pc.User)                .WithMany()                .HasForeignKey(pc => pc.UserId);        }    }

 

If the description is incorrect, please note it in the comments.