如何在Entity Framework Core 1.0 RTM中關閉級聯刪除

Question

嗨，我有帶有Entity Framework Core 1.0 RTM和SQL Server的MVC 6應用程序，當我嘗試生成數據庫表時，出現“引入FOREIGN KEY約束可能導致循環或多個級聯路徑”錯誤。

我的模型類如下：

類別模型：

 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; }
}

站台型號：

 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; }
}

VariableRecord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; }
}

變量設置模型：

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; }
}

可變模型：

 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; }
}

因此，我的代碼Category-> Station-> VariableRecord和Category-> VariableSetting-> VariableRecord中也有Cascade刪除路由，因此我嘗試使用Fluent API將上下文類別中的路由Category-> VariableSetting-> VariableRecord禁用。下面：

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

但是我仍然得到如下：

System.Data.SqlClient.SqlException（0x80131904）：在表'VariableSetting'上引入FOREIGN KEY約束'FK_VariableSetting_Category_CategoryId'可能會導致循環或多個級聯路徑。請指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY約束。

我已經在這些代碼上停留了幾天，但仍然無濟於事，請幫助！

Answer 1

使用DeleteBehavior.Restrict而不是DeleteBehavior.Cascade 。

您已經有多個級聯路徑，因此，如果要（確定，您需要）禁用其中之一的級聯，請使用DeleteBehavior.Restrict 。

Answer 2

如果遵循命名約定，則只需要類定義和一些注釋（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>();
}

如果要使用其他名稱，請取消注釋所有注釋並修復名稱。

創建的（SQLite）sql結構為

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;

如您所見，無需關閉層疊刪除：o）