如何将字符串键改为int [英] How to change string key to int

问题描述

我使用C＃EntityFramework和CodeFirst。我也使用迁移（自动和手动迁移）。

我有一个模型 -

  public class MyClass 
 {
 public string Key {set;得到; } 
 public string Something {set;得到; 
} 
  

而且我已经有一个数据库与行。

现在我想更改模型：

a。将密钥列更改为名称（这不是迁移问题，特别是自动迁移）

b。 添加一个新的属性 - 将会是身份（1，2，3 ...）的intKey。

这样做而不删除现有行？ （我想让他们得到一个自动的id）

解决方案

我决定测试一下。我从这个类开始，添加了迁移，更新了数据库，并插入了一些数据：

  public class MyClass 
 {
 [Key] //添加它以摆脱错误：
 // EntityType'Class1'没有定义键。定义此EntityType的键。 
 public string Key {set;得到; } 
 public string Something {set;得到; } 
} 
  

然后我将其更改为此并运行了第二次迁移。

  public class MyClass 
 {
 public int ID {get;组; } 
 public string Key {set;得到; } 
 public string Something {set;得到; } 
} 
  

这是生成的迁移。默认情况下，EF将创建一个名称为ID的整数列，其中标识为true：

  public override void Up 
 {
 DropPrimaryKey（dbo.MyClasses）; 
 AddColumn（dbo.MyClasses，ID，c => c.Int（nullable：false，identity：true））; 
 AlterColumn（dbo.MyClasses，Key，c => c.String（））; 
 AddPrimaryKey（dbo.MyClasses，ID）; 
} 
  

然后我更改了键到名称并运行另一个迁移。但是为了避免丢失数据，我在列删除之前添加了一些sql：

  public override void Up（）
 {
 AddColumn（dbo.MyClasses，Name，c => c.String（））; 
 Sql（UPDATE dbo.MyClasses SET Name = [Key]）; //手动添加到迁移
 DropColumn（dbo.MyClasses，Key）; 
} 
 
 public override void Down（）
 {
 AddColumn（dbo.MyClasses，Key，c => c.String（）） ; 
 Sql（UPDATE dbo.MyClasses SET [Key] = Name）; //手动添加到迁移
 DropColumn（dbo.MyClasses，Name）; 
} 
  

I use C# EntityFramework and CodeFirst. Also I use migrations (automatic & manual migrations).

I have a model -

public class MyClass
{
    public string Key { set; get; }
    public string Something { set; get; } 
}

And I already have a database with rows.

Now I want to change the model :

a. Change "Key" column to "Name" (which is not a problem with migration, especially automatic migrations)

b. Add a new property - an int "Key" that will be identity (1, 2, 3...).

How can I do that without deleting the existing rows? (I want them to get an automatic id)

解决方案

I decided to test this out. I started with this class, added a migration, updated the database, and inserted some data:

public class MyClass
{
    [Key]//Added this to get rid of the error: 
         //EntityType 'Class1' has no key defined. Define the key for this EntityType.
    public string Key { set; get; }
    public string Something { set; get; } 
}

Then I changed it to this and ran a second migration.

public class MyClass
{
    public int ID { get; set; }
    public string Key { set; get; }
    public string Something { set; get; } 
}

Here is the generated migration. By default, EF will make an integer column named "ID" the key - with identity true:

public override void Up()
{
    DropPrimaryKey("dbo.MyClasses");
    AddColumn("dbo.MyClasses", "ID", c => c.Int(nullable: false, identity: true));
    AlterColumn("dbo.MyClasses", "Key", c => c.String());
    AddPrimaryKey("dbo.MyClasses", "ID");
}

Then I changed Key to Name and ran another migration. But to avoid losing data, I added some sql before the column is dropped:

public override void Up()
{
    AddColumn("dbo.MyClasses", "Name", c => c.String());
    Sql("UPDATE dbo.MyClasses SET Name = [Key]"); //Manually added to migration
    DropColumn("dbo.MyClasses", "Key");
}

public override void Down()
{
    AddColumn("dbo.MyClasses", "Key", c => c.String());
    Sql("UPDATE dbo.MyClasses SET [Key] = Name"); //Manually added to migration
    DropColumn("dbo.MyClasses", "Name");
}

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