EF 6基于代码的迁移：向现有实体添加非null属性 [英] EF 6 Code-Based Migration: Add not null property to existing entity

问题描述

我想在现有表中添加非空的前导键列。

I want to add a not-null, foreing key column to an existing table.

环境：EF 6，Code-First ，基于代码的迁移

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 ); 

异常消息：

UPDATE语句与FOREIGN KEY约束
FK_dbo.Collection_dbo.Currency_CurrencyID冲突。
表 dbo.Currency的 CurrencyID列中发生冲突。

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

推荐答案

问题已解决，这里按顺序执行我遵循的步骤：

Problem solved, here are enumerated by order the steps i followed:

1. 将外键属性映射更改为不需要


2. 仅种子主键值


3. 更新数据库


4. 将属性改回必需


5. 添加新的迁移并为外键列的值填充


6. 更新数据库

1. Change the foreign key property mapping to Not Required
2. Seed only the primary key values
3. Update-Database
4. Change back the property to Required
5. Add new migration and seed the values for foreign key column
6. Update-Database

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