c# - 在尝试添加迁移时，我收到以下错误，我的数据库尚未创建，所以我不知道如何启用它

Question

错误：

在表 'Subjects' 上引入 FOREIGN KEY 约束 'FK_dbo.Subjects_dbo.Categories_CategoryID' 可能会导致循环或多个级联路径。指定 ON DELETE NO ACTION 或 ON UPDATE NO ACTION，或修改其他 FOREIGN KEY 约束。

无法创建约束。请参阅以前的错误。

我不知道如何启用on delete no action，因为尚未创建数据库

这些是实体类

public class BaseEntity
{
    public int ID { get; set; }

    [DisplayName("Name") ]
    public  string Title { get; set; }
    public string Description { get; set; }
}

public class Category : BaseEntity
{
}

public class Subject : BaseEntity
{
    public virtual Category Category { get; set; }
    public int CategoryID { get; set; }
}

public class Quiz
{
    public int ID { get; set; }
    public string Summary { get; set; }
    public string QuizName { get; set; }
    public int Hours { get; set; }
    public int Minutes { get; set; }

    public virtual Category Category { get; set; }
    public int CategoryID { get; set; }

    public virtual Subject Subject { get; set; }
    public int SubjectID { get; set; }

    public List<Question> Questions { get; set; }
}

public class Question
{
    public int ID { get; set; }
    public Quiz Quiz { get; set; }
    public int QuizID { get; set; }
       
    public string question { get; set; }
    public List<Options> options { get; set; }
}

public class Options
{
    public int ID { get; set; }
        
    public int QuizID { get; set; }
    public Question Question { get; set; }
    public int QuestionID { get; set; }
    public string option { get; set; }
    public bool isOption { get; set; }
}

早些时候我设置了外键 nullable ，现在它们不可为空，但我仍然得到同样的错误。

这是创建的迁移类：

public partial class intial : DbMigration
{
        public override void Up()
        {
            CreateTable(
                "dbo.Categories",
                c => new
                    {
                        ID = c.Int(nullable: false, identity: true),
                        Title = c.String(),
                        Description = c.String(),
                    })
                .PrimaryKey(t => t.ID);
            
            CreateTable(
                "dbo.Options",
                c => new
                    {
                        ID = c.Int(nullable: false, identity: true),
                        QuizID = c.Int(nullable: false),
                        QuestionID = c.Int(nullable: false),
                        option = c.String(),
                        isOption = c.Boolean(nullable: false),
                    })
                .PrimaryKey(t => t.ID)
                .ForeignKey("dbo.Questions", t => t.QuestionID, cascadeDelete: true)
                .Index(t => t.QuestionID);
            
            CreateTable(
                "dbo.Questions",
                c => new
                    {
                        ID = c.Int(nullable: false, identity: true),
                        QuizID = c.Int(nullable: false),
                        question = c.String(),
                    })
                .PrimaryKey(t => t.ID)
                .ForeignKey("dbo.Quizs", t => t.QuizID, cascadeDelete: true)
                .Index(t => t.QuizID);
            
            CreateTable(
                "dbo.Quizs",
                c => new
                    {
                        ID = c.Int(nullable: false, identity: true),
                        Summary = c.String(),
                        QuizName = c.String(),
                        Hours = c.Int(nullable: false),
                        Minutes = c.Int(nullable: false),
                        CategoryID = c.Int(nullable: false),
                        SubjectID = c.Int(nullable: false),
                    })
                .PrimaryKey(t => t.ID)
                .ForeignKey("dbo.Categories", t => t.CategoryID, cascadeDelete: true)
                .ForeignKey("dbo.Subjects", t => t.SubjectID, cascadeDelete: true)
                .Index(t => t.CategoryID)
                .Index(t => t.SubjectID);
            
            CreateTable(
                "dbo.Subjects",
                c => new
                    {
                        ID = c.Int(nullable: false, identity: true),
                        CategoryID = c.Int(nullable: false),
                        Title = c.String(),
                        Description = c.String(),
                    })
                .PrimaryKey(t => t.ID)
                .ForeignKey("dbo.Categories", t => t.CategoryID, cascadeDelete: true)
                .Index(t => t.CategoryID);
            
            CreateTable(
                "dbo.AspNetRoles",
                c => new
                    {
                        Id = c.String(nullable: false, maxLength: 128),
                        Name = c.String(nullable: false, maxLength: 256),
                    })
                .PrimaryKey(t => t.Id)
                .Index(t => t.Name, unique: true, name: "RoleNameIndex");
            
            CreateTable(
                "dbo.AspNetUserRoles",
                c => new
                    {
                        UserId = c.String(nullable: false, maxLength: 128),
                        RoleId = c.String(nullable: false, maxLength: 128),
                    })
                .PrimaryKey(t => new { t.UserId, t.RoleId })
                .ForeignKey("dbo.AspNetRoles", t => t.RoleId, cascadeDelete: true)
                .ForeignKey("dbo.AspNetUsers", t => t.UserId, cascadeDelete: true)
                .Index(t => t.UserId)
                .Index(t => t.RoleId);
            
            CreateTable(
                "dbo.UserQuizDetails",
                c => new
                    {
                        ID = c.Int(nullable: false, identity: true),
                        UserID = c.String(),
                        QuizID = c.Int(nullable: false),
                        QuestionID = c.Int(nullable: false),
                        OptionID = c.Int(),
                    })
                .PrimaryKey(t => t.ID)
                .ForeignKey("dbo.Options", t => t.OptionID)
                .ForeignKey("dbo.Questions", t => t.QuestionID, cascadeDelete: true)
                .ForeignKey("dbo.Quizs", t => t.QuizID, cascadeDelete: true)
                .Index(t => t.QuizID)
                .Index(t => t.QuestionID)
                .Index(t => t.OptionID);
            
            CreateTable(
                "dbo.AspNetUsers",
                c => new
                    {
                        Id = c.String(nullable: false, maxLength: 128),
                        Email = c.String(maxLength: 256),
                        EmailConfirmed = c.Boolean(nullable: false),
                        PasswordHash = c.String(),
                        SecurityStamp = c.String(),
                        PhoneNumber = c.String(),
                        PhoneNumberConfirmed = c.Boolean(nullable: false),
                        TwoFactorEnabled = c.Boolean(nullable: false),
                        LockoutEndDateUtc = c.DateTime(),
                        LockoutEnabled = c.Boolean(nullable: false),
                        AccessFailedCount = c.Int(nullable: false),
                        UserName = c.String(nullable: false, maxLength: 256),
                    })
                .PrimaryKey(t => t.Id)
                .Index(t => t.UserName, unique: true, name: "UserNameIndex");
            
            CreateTable(
                "dbo.AspNetUserClaims",
                c => new
                    {
                        Id = c.Int(nullable: false, identity: true),
                        UserId = c.String(nullable: false, maxLength: 128),
                        ClaimType = c.String(),
                        ClaimValue = c.String(),
                    })
                .PrimaryKey(t => t.Id)
                .ForeignKey("dbo.AspNetUsers", t => t.UserId, cascadeDelete: true)
                .Index(t => t.UserId);
            
            CreateTable(
                "dbo.AspNetUserLogins",
                c => new
                    {
                        LoginProvider = c.String(nullable: false, maxLength: 128),
                        ProviderKey = c.String(nullable: false, maxLength: 128),
                        UserId = c.String(nullable: false, maxLength: 128),
                    })
                .PrimaryKey(t => new { t.LoginProvider, t.ProviderKey, t.UserId })
                .ForeignKey("dbo.AspNetUsers", t => t.UserId, cascadeDelete: true)
                .Index(t => t.UserId);
            
        }
        
        public override void Down()
        {
            DropForeignKey("dbo.AspNetUserRoles", "UserId", "dbo.AspNetUsers");
            DropForeignKey("dbo.AspNetUserLogins", "UserId", "dbo.AspNetUsers");
            DropForeignKey("dbo.AspNetUserClaims", "UserId", "dbo.AspNetUsers");
            DropForeignKey("dbo.UserQuizDetails", "QuizID", "dbo.Quizs");
            DropForeignKey("dbo.UserQuizDetails", "QuestionID", "dbo.Questions");
            DropForeignKey("dbo.UserQuizDetails", "OptionID", "dbo.Options");
            DropForeignKey("dbo.AspNetUserRoles", "RoleId", "dbo.AspNetRoles");
            DropForeignKey("dbo.Quizs", "SubjectID", "dbo.Subjects");
            DropForeignKey("dbo.Subjects", "CategoryID", "dbo.Categories");
            DropForeignKey("dbo.Questions", "QuizID", "dbo.Quizs");
            DropForeignKey("dbo.Quizs", "CategoryID", "dbo.Categories");
            DropForeignKey("dbo.Options", "QuestionID", "dbo.Questions");
            DropIndex("dbo.AspNetUserLogins", new[] { "UserId" });
            DropIndex("dbo.AspNetUserClaims", new[] { "UserId" });
            DropIndex("dbo.AspNetUsers", "UserNameIndex");
            DropIndex("dbo.UserQuizDetails", new[] { "OptionID" });
            DropIndex("dbo.UserQuizDetails", new[] { "QuestionID" });
            DropIndex("dbo.UserQuizDetails", new[] { "QuizID" });
            DropIndex("dbo.AspNetUserRoles", new[] { "RoleId" });
            DropIndex("dbo.AspNetUserRoles", new[] { "UserId" });
            DropIndex("dbo.AspNetRoles", "RoleNameIndex");
            DropIndex("dbo.Subjects", new[] { "CategoryID" });
            DropIndex("dbo.Quizs", new[] { "SubjectID" });
            DropIndex("dbo.Quizs", new[] { "CategoryID" });
            DropIndex("dbo.Questions", new[] { "QuizID" });
            DropIndex("dbo.Options", new[] { "QuestionID" });
            DropTable("dbo.AspNetUserLogins");
            DropTable("dbo.AspNetUserClaims");
            DropTable("dbo.AspNetUsers");
            DropTable("dbo.UserQuizDetails");
            DropTable("dbo.AspNetUserRoles");
            DropTable("dbo.AspNetRoles");
            DropTable("dbo.Subjects");
            DropTable("dbo.Quizs");
            DropTable("dbo.Questions");
            DropTable("dbo.Options");
            DropTable("dbo.Categories");
        }
    }
}

运行 update-database 命令后发生错误。

标签： c#asp.netasp.net-mvc-5

Answer 1

在 Subject 和 Categorie 的关系上添加带有正确参数的 CascaseOnDelete() 方法。提供您的代码将给出更好的答案