如何在代码优先的Entity Framework流利API中指定多列UNIQUE约束 [英] How to specify a multi-column UNIQUE constraint in code-first Entity Framework fluent API

问题描述

假设我有以下实体：

public class Calendar{
    public int ID{get;set;}
    public ICollection<Day> Days { get; set; }
}
public class Day{
    public int ID{get;set;}
    public DateTime Date{get;set;}
    public int CalendarID{get;set;}
}

这是与<$ c的一对多关系$ c> CalendarID 作为外键。问题是我还想确保每个日期在每个日历中仅存在一次。也就是说，没有两天都有相同的 Date 和相同的 CalendarID 。在原始SQL中，我可以通过以下方式做到这一点：

This is a one-to-many relationship with CalendarID as a foreign key. The issue is I also want to make sure that each date exists only once in each calendar. That is, no two days have both the same Date and same CalendarID. In raw SQL I can do this by:

ALTER TABLE Days
ADD CONSTRAINT UN_Day UNIQUE ([Date],CalendarID);

但是，Entity Framework在自动创建表格时不知道我要这个。如何在fluent API中指定它？

However, Entity Framework won't know I want this when it creates the table automatically. How can I specify this in the fluent API?

推荐答案

请参见在一个或多个属性上配置索引。

在您的映射类中，假设它从 EntityTypeConfiguration< Day> 扩展，则需要添加使用System.Data.Entity.Infrastructure.Annotations; 并执行以下操作：

In your mapping class, assuming it extends from EntityTypeConfiguration<Day> then you will need to add using System.Data.Entity.Infrastructure.Annotations; and do the following:

this.Property(x => x.Date)
    .HasColumnAnnotation(IndexAnnotation.AnnotationName,
                 new IndexAnnotation(new IndexAttribute("UN_Day", 0) { IsUnique = true }));

this.Property(x => x.CalendarID)
    .HasColumnAnnotation(IndexAnnotation.AnnotationName,
                 new IndexAnnotation(new IndexAttribute("UN_Day", 1) { IsUnique = true }));

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