entity-framework - EF 6 基于代码的迁移 : Add not null property to existing entity

Question

我想向现有表添加一个非空的外键列。

Environment: EF 6,Code-First, Code-Based Migration

//Code from Migration class for new entity Currency
CreateTable("dbo.Currency",
                c => new
                    {
                        CurrencyID = c.Int(nullable: false, identity: true),
                        Code = c.String(nullable: false, maxLength: 3, fixedLength: true, unicode: false),
                        Denomination = c.String(nullable: false, maxLength: 50, unicode: false),
                    })
                .PrimaryKey(t => t.CurrencyID);

AddColumn("dbo.Collection", "CurrencyID", c => c.Int(nullable: false));

//Code from Seed() method in Configuration class 
context.Currencies.AddOrUpdate(
    new Currency
    {
        Code = "USD",
        Denomination = "Dollar"
    }
);

//Here i get an exception. Collection is the existing table
context.Database.ExecuteSqlCommand( "update collection set CurrencyID = 1 ); 

异常信息:

The UPDATE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Collection_dbo.Currency_CurrencyID". The conflict occurred in table "dbo.Currency", column 'CurrencyID'.

Answer 1

问题已解决，这里按顺序列举了我遵循的步骤:

1. 将外键属性映射更改为不需要
2. 仅作为主键值的种子
3. 更新数据库
4. 将属性改回 Required
5. 添加新的迁移并为外键列的值设置种子
6. 更新数据库