c# - 在 Entity Framework 中更改数据库结构和移动数据

Question

我的数据库有如下实体 Driver 和 DriverWork:

已编辑:

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

    public string Name { get; set; }

    public string Description { get; set; }
}

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

    public string FromLocation { get; set; }

    public string ToLocation { get; set; }

    public int Price { get; set; }

    public DateTime Date { get; set; }

    public int DriverId { get; set; }

    [ForeignKey(nameof(DriverId))]
    public Driver Driver { get; set; }
}

并且在这些实体中包含许多行。现在我添加了另一个名为 WorkPage 的实体，它改变了与此的关系:

DriverWork --> 驱动程序

对此:

DriverWork --> WorkPage --> Driver

修改后的模型(Driver还是旧的):

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

    public string Name { get; set; }

    public string Description { get; set; }
}

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

    public byte CommissionPercentage { get; set; }

    public bool IsClosed { get; set; }

    public DateTime? DateClosed { get; set; }

    public int DriverId { get; set; }

    [ForeignKey(nameof(DriverId))]
    public Driver Driver { get; set; }
}

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

    public string FromLocation { get; set; }

    public string ToLocation { get; set; }

    public int Price { get; set; }

    public DateTime Date { get; set; }

    public int WorkPageId { get; set; }

    [ForeignKey(nameof(WorkPageId))]
    public WorkPage WorkPage { get; set; }
}

添加新迁移后，我知道我应该在 Up 方法中进行更改，因为一些驱动程序目前没有任何 WorkPage，我至少应该为它们添加一个 WorkPage，当前的 DriverWork 项也必须将它们的 DriverId 值更改为关联的有效 WorkPageId使用那个 Driver。但我不知道我应该如何在 EF6 中进行此迁移？

在 Up 方法中没有做任何更改，EF 在运行 update-database 命令后给出了这个错误:

The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.DriverWorks_dbo.WorkPages_WorkPageId". The conflict occurred in database "{dblocation}\KHORSHIDDATA.MDF", table "dbo.WorkPages", column 'Id'.

有什么帮助吗？

Answer 1

因为这是一个艰难的转变，我建议分两次执行。

首先，保留 DriverWork 中的 DriverId FK，并使 WorkPage 中的 DriverId 可选(可为空):

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

    public byte CommissionPercentage { get; set; }

    public bool IsClosed { get; set; }

    public DateTime? DateClosed { get; set; }

    public int? DriverId { get; set; }

    [ForeignKey(nameof(DriverId))]
    public Driver Driver { get; set; }
}

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

    public string FromLocation { get; set; }

    public string ToLocation { get; set; }

    public int Price { get; set; }

    public DateTime Date { get; set; }

    public int DriverId { get; set; }

    [ForeignKey(nameof(DriverId))]
    public Driver Driver { get; set; }

    public int WorkPageId { get; set; }

    [ForeignKey(nameof(WorkPageId))]
    public WorkPage WorkPage { get; set; }
}

生成新的迁移。它应该是这样的:

public override void Up()
{
    CreateTable(
        "dbo.WorkPage",
        c => new
            {
                Id = c.Int(nullable: false, identity: true),
                CommissionPercentage = c.Byte(nullable: false),
                IsClosed = c.Boolean(nullable: false),
                DateClosed = c.DateTime(),
                DriverId = c.Int(nullable: false),
            })
        .PrimaryKey(t => t.Id)
        .ForeignKey("dbo.Driver", t => t.DriverId, cascadeDelete: true)
        .Index(t => t.DriverId);

    AddColumn("dbo.DriverWork", "WorkPageId", c => c.Int());
    CreateIndex("dbo.DriverWork", "WorkPageId");
    AddForeignKey("dbo.DriverWork", "WorkPageId", "dbo.WorkPage", "Id");
}

执行迁移。然后通过从 DriverWork 中删除 Driver 并使 WorkPage 中的 DriverId 成为必需的(非空)来恢复所需的实体模型:

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

    public byte CommissionPercentage { get; set; }

    public bool IsClosed { get; set; }

    public DateTime? DateClosed { get; set; }

    public int DriverId { get; set; }

    [ForeignKey(nameof(DriverId))]
    public Driver Driver { get; set; }
}

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

    public string FromLocation { get; set; }

    public string ToLocation { get; set; }

    public int Price { get; set; }

    public DateTime Date { get; set; }

    public int WorkPageId { get; set; }

    [ForeignKey(nameof(WorkPageId))]
    public WorkPage WorkPage { get; set; }
}

生成第二个新迁移。它应该看起来像这样:

public override void Up()
{
    DropForeignKey("dbo.DriverWork", "DriverId", "dbo.Driver");
    DropForeignKey("dbo.DriverWork", "WorkPageId", "dbo.WorkPages");
    DropIndex("dbo.DriverWork", new[] { "DriverId" });
    DropIndex("dbo.DriverWork", new[] { "WorkPageId" });
    AlterColumn("dbo.DriverWork", "WorkPageId", c => c.Int(nullable: false));
    CreateIndex("dbo.DriverWork", "WorkPageId");
    AddForeignKey("dbo.DriverWork", "WorkPageId", "dbo.WorkPage", "Id", cascadeDelete: true);
    DropColumn("dbo.DriverWork", "DriverId");
}

使用 Sql 方法来填充 WorkPage 表数据并更新 WorkTableId FK，然后再将其设为必需。例如，在 Up 方法的开头插入以下内容:

Sql(@"insert into dbo.WorkPage (CommissionPercentage, IsClosed, DateClosed, DriverId) select 0, 0, null, DriverId from dbo.DriverWork");
Sql(@"update dbo.DriverWork set WorkPageId = WP.Id from dbo.DriverWork DW join dbo.WorkPage WP on DW.DriverId = WP.DriverId");

执行迁移，您就完成了。

实际上，转换数据的 Sql 调用可以在第一次迁移 Up 方法的末尾。

事先了解所有这些，您可以保持新模型不变(跳过第一步)，只需将生成的迁移 Up 方法替换为上述两者的联合，例如

public override void Up()
{
    CreateTable(
        "dbo.WorkPage",
        c => new
            {
                Id = c.Int(nullable: false, identity: true),
                CommissionPercentage = c.Byte(nullable: false),
                IsClosed = c.Boolean(nullable: false),
                DateClosed = c.DateTime(),
                DriverId = c.Int(nullable: false),
            })
        .PrimaryKey(t => t.Id)
        .ForeignKey("dbo.Driver", t => t.DriverId, cascadeDelete: true)
        .Index(t => t.DriverId);

    AddColumn("dbo.DriverWork", "WorkPageId", c => c.Int());
    CreateIndex("dbo.DriverWork", "WorkPageId");
    AddForeignKey("dbo.DriverWork", "WorkPageId", "dbo.WorkPage", "Id");

    Sql(@"insert into dbo.WorkPage (CommissionPercentage, IsClosed, DateClosed, DriverId) select 0, 0, null, DriverId from dbo.DriverWork");
    Sql(@"update dbo.DriverWork set WorkPageId = WP.Id from dbo.DriverWork DW join dbo.WorkPage WP on DW.DriverId = WP.DriverId");

    DropForeignKey("dbo.DriverWork", "DriverId", "dbo.Driver");
    DropForeignKey("dbo.DriverWork", "WorkPageId", "dbo.WorkPages");
    DropIndex("dbo.DriverWork", new[] { "DriverId" });
    DropIndex("dbo.DriverWork", new[] { "WorkPageId" });
    AlterColumn("dbo.DriverWork", "WorkPageId", c => c.Int(nullable: false));
    CreateIndex("dbo.DriverWork", "WorkPageId");
    AddForeignKey("dbo.DriverWork", "WorkPageId", "dbo.WorkPage", "Id", cascadeDelete: true);
    DropColumn("dbo.DriverWork", "DriverId");
}