如何在 Entity Framework Core 1.0 RTM 中关闭级联删除

Question

您好，我有带有 Entity Framework Core 1.0 RTM 和 SQL 服务器的 MVC 6 应用程序，当我尝试生成数据库表时，出现“引入 FOREIGN KEY 约束可能导致循环或多个级联路径”错误。

我的模型类如下：

类别模型：

 public class Category
{
    public Category()
    {
        this.VariableSettings = new List<VariableSetting>();
    }
    public int CategoryId { get; set; }

    public string CategoryName { get; set; }

    public List<VariableSetting> VariableSettings { get; set; }

    public List<Station> Stations { get; set; }
}

车站型号：

 public class Station
{
    public int StationId { get; set; }
    public string StationName { get; set; }

    public double? Longitude { get; set; }
    public double? Latitude { get; set; }

    public List<VariableRecord> VariableRecords { get; set; }

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

变量记录模型：

 public class VariableRecord
{
    [Key]
    public int VariableRecordId { get; set; }
    public double Value { get; set; }
    public DateTime RecordDate { get; set; }

    public int StationId { get; set; }
    public Station Station { get; set; }

    public int VarSettingId{ get; set; }
    public virtual VariableSetting VariableSetting { get; set; }
}

变量设置模型：

public class VariableSetting
{
    [Key]
    public int VarSettingId { get; set; }
    public int Sequence { get; set; }
    public double? MinimumValue { get; set; }
    public double? MaximumValue { get; set; }

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

    public int VariableId { get; set; }
    public Variable Variable { get; set; }

    public List<VariableRecord> VariableRecords { get; set; }
}

变量模型：

 public class Variable
{
    public int VariableId { get; set; }

    public string VariableName { get; set; }

    public string Description { get; set; }

    public string Unit { get; set; }

    public List<VariableSetting> VariableSettings { get; set; }
}

所以，在我的代码 Category->Station->VariableRecord 和 Category->VariableSetting->VariableRecord 中也有级联删除路由，所以我试图在上下文类中禁用路由 Category->VariableSetting->VariableRecord Fluent API 如下：

builder.Entity<VariableRecord>()
        .HasOne(pt => pt.VariableSetting)
        .WithMany(p => p.VariableRecords)
        .HasForeignKey(pt => pt.VarSettingId)
        .OnDelete(DeleteBehavior.Cascade);

但是我仍然得到以下相同的结果：

System.Data.SqlClient.SqlException (0x80131904)：引入 FOREIGN 表上的 KEY 约束“FK_VariableSetting_Category_CategoryId” 'VariableSetting' 可能会导致循环或多个级联路径。请指定 ON DELETE NO ACTION 或 ON UPDATE NO ACTION，或修改其他 FOREIGN 关键约束。

我在这些代码上卡了几天，但仍然无处可去，请帮助！

Answer 1

使用DeleteBehavior.Restrict 而不是DeleteBehavior.Cascade。

您已经有多个级联路径，因此如果您想要（好的，您需要）禁用其中一个的级联 - 使用 DeleteBehavior.Restrict。

Answer 2

如果您遵循命名约定，您只需要类定义和一些注释（使用 EF Core 1.0.1）

public class Category
{
    [Key]
    public int Id { get; set; }
    [Required]
    public string Name { get; set; }

    //[InverseProperty( nameof( VariableSetting.Category ) )]
    public virtual ICollection<VariableSetting> VariableSettings { get; set; }
        = new List<VariableSetting>();

    //[InverseProperty( nameof( Station.Category ) )]
    public virtual ICollection<Station> Stations { get; set; } 
        = new List<Station>();
}

public class Station
{
    [Key]
    public int Id { get; set; }
    [Required]
    public string Name { get; set; }
    public double? Longitude { get; set; }
    public double? Latitude { get; set; }

    //[InverseProperty( nameof( VariableRecord.Station ) )]
    public virtual ICollection<VariableRecord> VariableRecords { get; set; }
        = new List<VariableRecord>();

    [Required]
    public int CategoryId { get; set; }

    //[ForeignKey( nameof( CategoryId ) )]
    public virtual Category Category { get; set; }
}

public class VariableRecord
{
    [Key]
    public int Id { get; set; }
    public double Value { get; set; }
    public DateTime RecordDate { get; set; }

    [Required]
    public int StationId { get; set; }

    //[ForeignKey( nameof( StationId ) )]
    public virtual Station Station { get; set; }

    [Required]
    public int VariableSettingId { get; set; }

    //[ForeignKey( nameof( VariableSettingId ) )]
    public virtual VariableSetting VariableSetting { get; set; }
}

public class VariableSetting
{
    [Key]
    public int Id { get; set; }
    public int Sequence { get; set; }
    public double? MinimumValue { get; set; }
    public double? MaximumValue { get; set; }

    [Required]
    public int CategoryId { get; set; }

    //[ForeignKey( nameof( CategoryId ) )]
    public virtual Category Category { get; set; }

    [Required]
    public int VariableId { get; set; }

    //[ForeignKey( nameof( VariableId ) )]
    public virtual Variable Variable { get; set; }

    //[InverseProperty( nameof( VariableRecord.VariableSetting ) )]
    public virtual ICollection<VariableRecord> VariableRecords { get; set; }
        = new List<VariableRecord>();
}

public class Variable
{
    [Key]
    public int Id { get; set; }

    [Required]
    public string Name { get; set; }
    public string Description { get; set; }
    public string Unit { get; set; }

    //[InverseProperty( nameof( VariableSetting.Variable ) )]
    public virtual ICollection<VariableSetting> VariableSettings { get; set; }
        = new List<VariableSetting>();
}

如果您想使用其他名称，请取消注释所有注释并修复名称。

创建的（SQLite）sql结构是

PRAGMA foreign_keys = false;

-- ----------------------------
--  Table structure for "Categories"
-- ----------------------------
DROP TABLE IF EXISTS "Categories";
CREATE TABLE "Categories" (
    "Id" INTEGER NOT NULL CONSTRAINT "PK_Categories" PRIMARY KEY AUTOINCREMENT,
    "Name" TEXT NOT NULL
);

-- ----------------------------
--  Table structure for "Stations"
-- ----------------------------
DROP TABLE IF EXISTS "Stations";
CREATE TABLE "Stations" (
    "Id" INTEGER NOT NULL CONSTRAINT "PK_Stations" PRIMARY KEY AUTOINCREMENT,
    "CategoryId" INTEGER NOT NULL,
    "Latitude" REAL,
    "Longitude" REAL,
    "Name" TEXT NOT NULL,
    CONSTRAINT "FK_Stations_Categories_CategoryId" FOREIGN KEY ("CategoryId") REFERENCES "Categories" ("Id") ON DELETE CASCADE
);

-- ----------------------------
--  Table structure for "Variable"
-- ----------------------------
DROP TABLE IF EXISTS "Variable";
CREATE TABLE "Variable" (
    "Id" INTEGER NOT NULL CONSTRAINT "PK_Variable" PRIMARY KEY AUTOINCREMENT,
    "Description" TEXT,
    "Name" TEXT NOT NULL,
    "Unit" TEXT
);

-- ----------------------------
--  Table structure for "VariableRecord"
-- ----------------------------
DROP TABLE IF EXISTS "VariableRecord";
CREATE TABLE "VariableRecord" (
    "Id" INTEGER NOT NULL CONSTRAINT "PK_VariableRecord" PRIMARY KEY AUTOINCREMENT,
    "RecordDate" TEXT NOT NULL,
    "StationId" INTEGER NOT NULL,
    "Value" REAL NOT NULL,
    "VariableSettingId" INTEGER NOT NULL,
    CONSTRAINT "FK_VariableRecord_Stations_StationId" FOREIGN KEY ("StationId") REFERENCES "Stations" ("Id") ON DELETE CASCADE,
    CONSTRAINT "FK_VariableRecord_VariableSetting_VariableSettingId" FOREIGN KEY ("VariableSettingId") REFERENCES "VariableSetting" ("Id") ON DELETE CASCADE
);

-- ----------------------------
--  Table structure for "VariableSetting"
-- ----------------------------
DROP TABLE IF EXISTS "VariableSetting";
CREATE TABLE "VariableSetting" (
    "Id" INTEGER NOT NULL CONSTRAINT "PK_VariableSetting" PRIMARY KEY AUTOINCREMENT,
    "CategoryId" INTEGER NOT NULL,
    "MaximumValue" REAL,
    "MinimumValue" REAL,
    "Sequence" INTEGER NOT NULL,
    "VariableId" INTEGER NOT NULL,
    CONSTRAINT "FK_VariableSetting_Categories_CategoryId" FOREIGN KEY ("CategoryId") REFERENCES "Categories" ("Id") ON DELETE CASCADE,
    CONSTRAINT "FK_VariableSetting_Variable_VariableId" FOREIGN KEY ("VariableId") REFERENCES "Variable" ("Id") ON DELETE CASCADE
);

-- ----------------------------
--  Indexes structure for table "Stations"
-- ----------------------------
CREATE INDEX "IX_Stations_CategoryId" ON "Stations" ("CategoryId");

-- ----------------------------
--  Indexes structure for table "VariableRecord"
-- ----------------------------
CREATE INDEX "IX_VariableRecord_StationId" ON "VariableRecord" ("StationId");
CREATE INDEX "IX_VariableRecord_VariableSettingId" ON "VariableRecord" ("VariableSettingId");

-- ----------------------------
--  Indexes structure for table "VariableSetting"
-- ----------------------------
CREATE INDEX "IX_VariableSetting_CategoryId" ON "VariableSetting" ("CategoryId");
CREATE INDEX "IX_VariableSetting_VariableId" ON "VariableSetting" ("VariableId");

PRAGMA foreign_keys = true;

如您所见，级联删除无需关闭:o)