Question

我有两个型号

public class ContractType
{
    public Guid ContractTypeId { get; set; }
    public string Name { get; set; }
}

public class JobPost : BasePost
{
    public ContractType ContractType { get; set; }
    public Guid ContractTypeId { get; set; }    
}

正如您所看到的，ContractTypeId是JobPost表中的外键。

然后，我使用代码优先将它们更新到数据库。

但我刚决定int代替ContractTypeId而不是Guid。所以我只是将ContractTypeId的数据类型更改为int并添加了迁移。两个表都没有数据。这就是我得到的

    public override void Up()
    {
        DropForeignKey("dbo.JobPosts", "ContractTypeId", "dbo.ContractTypes");
        DropIndex("dbo.JobPosts", new[] { "ContractTypeId" });
        DropPrimaryKey("dbo.ContractTypes");
        AlterColumn("dbo.ContractTypes", "ContractTypeId", c => c.Int(nullable: false, identity: true));
        AlterColumn("dbo.JobPosts", "ContractTypeId", c => c.Int(nullable: false));
        AddPrimaryKey("dbo.ContractTypes", "ContractTypeId");
        CreateIndex("dbo.JobPosts", "ContractTypeId");
        AddForeignKey("dbo.JobPosts", "ContractTypeId", "dbo.ContractTypes", "ContractTypeId", cascadeDelete: true);
    }

    public override void Down()
    {
        DropForeignKey("dbo.JobPosts", "ContractTypeId", "dbo.ContractTypes");
        DropIndex("dbo.JobPosts", new[] { "ContractTypeId" });
        DropPrimaryKey("dbo.ContractTypes");
        AlterColumn("dbo.JobPosts", "ContractTypeId", c => c.Guid(nullable: false));
        AlterColumn("dbo.ContractTypes", "ContractTypeId", c => c.Guid(nullable: false));
        AddPrimaryKey("dbo.ContractTypes", "ContractTypeId");
        CreateIndex("dbo.JobPosts", "ContractTypeId");
        AddForeignKey("dbo.JobPosts", "ContractTypeId", "dbo.ContractTypes", "ContractTypeId", cascadeDelete: true);
    }

但是，当我使用update-database更新数据库时，出现错误：

错误号码：206，状态：2，等级：16
操作数类型冲突：uniqueidentifier与int
不兼容

我知道因为我还没有为表格填充任何数据，所以我可以简单地删除并重新创建模型并更新它们。

但我想知道如何解决这个问题或如何更改ContractTypeId的数据类型。

谢谢你们

Answer 1

你去吧。因为你没有好的数据:)狡猾的是首先删除列并再次添加它们。但是我们不能将uniquiueidentitfier更改为int直接读取几个帖子，其中提到了 Change datatype of column to uniqueidentifier from bigint。因此我采用了迁移:)可能对其他喜欢先从EF代码执行此操作的人有所帮助。

public override void Up()
    {
        DropForeignKey("dbo.JobPosts", "ContractTypeId", "dbo.ContractTypes");
        DropIndex("dbo.JobPosts", new[] { "ContractTypeId" });
        DropPrimaryKey("dbo.ContractTypes");


        -- below line added manaully
        DropColumn("dbo.ContractTypes", "ContractTypeId");
        -- below line added manaully
        AddColumn("dbo.ContractTypes", "ContractTypeId", c => c.Int(nullable: false, identity: true));

        -- below line added manaully
        DropColumn("dbo.JobPosts", "ContractTypeId");

        -- below line added manaully
        AddColumn("dbo.JobPosts", "ContractTypeId", c => c.Int(nullable: false));


        AddPrimaryKey("dbo.ContractTypes", "ContractTypeId");
        CreateIndex("dbo.JobPosts", "ContractTypeId");
        AddForeignKey("dbo.JobPosts", "ContractTypeId", "dbo.ContractTypes", "ContractTypeId", cascadeDelete: true);
    }

如何在EF代码中首先更改外键的数据类型

1 个答案: