我已经为这个问题纠结了一段时间，不太明白发生了什么。我有一个卡片实体，它包含边(通常是2)-卡片和边都有一个阶段。我使用EF Codefirst迁移和迁移失败与此错误:
引入外键约束'FK_dbo.Sides_dbo。Cards_CardId”
表'Sides'可能会导致循环或多个级联路径。指定
DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他外键
约束。
这是我的Card实体:
public class Card
{
public Card()
{
Sides = new Collection<Side>();
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int CardId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
[ForeignKey("CardId")]
public virtual ICollection<Side> Sides { get; set; }
}
这是我的Side实体:
public class Side
{
public Side()
{
Stage = Stage.ONE;
}
[Key]
[Required]
public virtual int SideId { get; set; }
[Required]
public virtual Stage Stage { get; set; }
[Required]
public int CardId { get; set; }
[ForeignKey("CardId")]
public virtual Card Card { get; set; }
}
这是我的舞台实体:
public class Stage
{
// Zero
public static readonly Stage ONE = new Stage(new TimeSpan(0, 0, 0), "ONE");
// Ten seconds
public static readonly Stage TWO = new Stage(new TimeSpan(0, 0, 10), "TWO");
public static IEnumerable<Stage> Values
{
get
{
yield return ONE;
yield return TWO;
}
}
public int StageId { get; set; }
private readonly TimeSpan span;
public string Title { get; set; }
Stage(TimeSpan span, string title)
{
this.span = span;
this.Title = title;
}
public TimeSpan Span { get { return span; } }
}
奇怪的是，如果我添加以下到我的Stage类:
public int? SideId { get; set; }
[ForeignKey("SideId")]
public virtual Side Side { get; set; }
迁移成功。如果我打开SSMS并查看表格，我可以看到Stage_StageId已添加到Cards(正如预期/期望的那样)，但是Sides没有包含对Stage的引用(不预期)。
如果我再加上
[Required]
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int StageId { get; set; }
在Side类中，我看到StageId列添加到Side表中。
这是有效的，但是现在在整个应用程序中，任何对Stage的引用都包含一个SideId，这在某些情况下是完全不相关的。我想给我的卡和边实体一个基于上面的Stage类的Stage属性，如果可能的话，不要用引用属性污染Stage类……我做错了什么?
public partial class recommended_books : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.RecommendedBook",
c => new
{
RecommendedBookID = c.Int(nullable: false, identity: true),
CourseID = c.Int(nullable: false),
DepartmentID = c.Int(nullable: false),
Title = c.String(),
Author = c.String(),
PublicationDate = c.DateTime(nullable: false),
})
.PrimaryKey(t => t.RecommendedBookID)
.ForeignKey("dbo.Course", t => t.CourseID, cascadeDelete: false) // was true on migration
.ForeignKey("dbo.Department", t => t.DepartmentID, cascadeDelete: false) // was true on migration
.Index(t => t.CourseID)
.Index(t => t.DepartmentID);
}
public override void Down()
{
DropForeignKey("dbo.RecommendedBook", "DepartmentID", "dbo.Department");
DropForeignKey("dbo.RecommendedBook", "CourseID", "dbo.Course");
DropIndex("dbo.RecommendedBook", new[] { "DepartmentID" });
DropIndex("dbo.RecommendedBook", new[] { "CourseID" });
DropTable("dbo.RecommendedBook");
}
}
当你的迁移失败时，你有几个选择:
'引入外键约束'FK_dbo.RecommendedBook_dbo. '表“recommendations book”上的Department_DepartmentID'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，或修改其他外键约束。
无法创建约束或索引。见以前的错误。”
下面是一个使用“修改其他外键约束”的例子，在迁移文件中设置“cascadeDelete”为false，然后运行“update-database”。
public partial class recommended_books : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.RecommendedBook",
c => new
{
RecommendedBookID = c.Int(nullable: false, identity: true),
CourseID = c.Int(nullable: false),
DepartmentID = c.Int(nullable: false),
Title = c.String(),
Author = c.String(),
PublicationDate = c.DateTime(nullable: false),
})
.PrimaryKey(t => t.RecommendedBookID)
.ForeignKey("dbo.Course", t => t.CourseID, cascadeDelete: false) // was true on migration
.ForeignKey("dbo.Department", t => t.DepartmentID, cascadeDelete: false) // was true on migration
.Index(t => t.CourseID)
.Index(t => t.DepartmentID);
}
public override void Down()
{
DropForeignKey("dbo.RecommendedBook", "DepartmentID", "dbo.Department");
DropForeignKey("dbo.RecommendedBook", "CourseID", "dbo.Course");
DropIndex("dbo.RecommendedBook", new[] { "DepartmentID" });
DropIndex("dbo.RecommendedBook", new[] { "CourseID" });
DropTable("dbo.RecommendedBook");
}
}
当你的迁移失败时，你有几个选择:
'引入外键约束'FK_dbo.RecommendedBook_dbo. '表“recommendations book”上的Department_DepartmentID'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，或修改其他外键约束。
无法创建约束或索引。见以前的错误。”
下面是一个使用“修改其他外键约束”的例子，在迁移文件中设置“cascadeDelete”为false，然后运行“update-database”。
