c# - 执行 DbCommand 失败 - 引入 FOREIGN KEY 约束

Question

此处显示通过 dotnet-core 迁移更新数据库时出现以下错误。

        Failed executing DbCommand (48ms) [Parameters=[], CommandType='Text', CommandTimeout='30']
        CREATE TABLE [DepartmentSchool] (
        [DepartmentID] uniqueidentifier NOT NULL,
        [SchoolsId] uniqueidentifier NOT NULL,
        [Id] uniqueidentifier NOT NULL,
        CONSTRAINT [PK_DepartmentSchool] PRIMARY KEY ([SchoolsId], [DepartmentID]),
        CONSTRAINT [FK_DepartmentSchool_Department_DepartmentID] FOREIGN KEY ([DepartmentID]) REFERENCES [Department] ([ID]) ON DELETE CASCADE,
        CONSTRAINT [FK_DepartmentSchool_School_SchoolsId] FOREIGN KEY ([SchoolsId]) REFERENCES [School] ([ID]) ON DELETE CASCADE
    );

下面是实体关系类有:

学校类(class)(第一表):

public partial class Schools
{
    public Guid ID { get; set; }
    public string Name { get; set; }

    public Guid? CountryId { get; set; }
    public Country Country { get; set; }

    public ICollection<DepartmentSchool> DepartmentSchools { get; set; } 
}

部门类(class)(第二表):

public partial class Department
{
    public Guid ID { get; set; }
    public string Title { get; set; }

    public DateTime CreatedAt { get; set; }

    public ICollection<DepartmentSchool> DepartmentSchools { get; set; } 
}

DepartmentSchool类(class)(中表)

public class DepartmentSchool
    {
        public Guid Id { get; set; }

        public Guid DepartmentID { get; set; }
        public Department Department { get; set; }

        public Guid SchoolsId { get; set; }
        public Schools Schools { get; set; }
    }

在 modulbulider 中，它的关系定义如下:

 //Many to many relationship between School and Depatment
        modelBuilder.Entity<DepartmentSchool>()
            .HasKey(ds => new { ds.SchoolsId, ds.DepartmentID });
        modelBuilder.Entity<DepartmentSchool>()
            .HasOne(ds => ds.Department)
            .WithMany(d => d.DepartmentSchools)
            .HasForeignKey(ds => ds.DepartmentID);
        modelBuilder.Entity<DepartmentSchool>()
            .HasOne(ds => ds.Schools)
            .WithMany(d => d.DepartmentSchools)
            .HasForeignKey(ds => ds.SchoolsId);

Answer 1

通过允许引用中存在空值来禁用级联删除。

.OnDelete(DeleteBehavior.Restrict);

About Cascade Delete In Asp Core

例如:

modelBuilder.Entity<Invoice>()
            .HasOne(i => i.Customer)
            .WithMany(c => c.Invoices)
            .OnDelete(DeleteBehavior.Restrict);

Help link about reason error