Question

我的数据库具有这样的实体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; }
}

，并且在那些实体中包含许多行。现在，我添加了另一个名称为WorkPage的实体，它从此更改了关系：

DriverWork --> Driver

对此：

DriverWork --> WorkPage --> Driver

更改后的模型（Driver仍然是旧模型）：

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; }
}

添加新的迁移后，我知道我应该在Up方法中进行更改，因为某些驱动程序当前没有任何WorkPage，我应该至少添加一个{{1} }，因此，当前WorkPage项也必须将其DriverWork的值更改为与该DriverId关联的有效WorkPageId。但是我不知道该如何在EF6中进行迁移？

在不更改Driver方法的情况下，EF在运行Up命令后给出此错误：

update-database

有帮助吗？

Answer 1

正弦这是一个艰难的转变，我建议进行两次通过。

首先，将DriverId FK保留在DriverWork中，并使DriverId中的WorkPage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。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Driver中删除DriverWork并将DriverId中的WorkPage设为必需（非null）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方法填充WorkPage表数据并在需要之前更新WorkTableId FK。例如，将以下内容插入Up方法的开头：

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");

执行迁移即可完成。

实际上，转换数据的Sql调用可以在第一个迁移Up方法的结尾。

事先了解了所有这些信息，您可以按原样保留新模型（跳过第一步），只需将生成的迁移Up方法替换为以上两者的并集即可，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");
}

更改数据库结构并在实体框架中移动数据

1 个答案: