EF6代码中的唯一多列 [英] Unique multiple column in EF6 codefirst

问题描述

我有一个类似于以下类别的电子邮件：

I have a class Email that looks like :

public class Email
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }
    public string Subject { get; set; }
    public string Body { get; set; }
    public string From { get; set; }
    public DateTime SentOn { get; set; }
    public List<string> To { get; set; }
}

为了确保唯一性，我在上做了一个复合键主题，发件人和 SentOn

To ensure uniqueness I made a compound key on Subject, From and SentOn

这产生了一个问题，即主题超过128个字符时，验证将失败。因此，我只在其上放置了 [MaxLength] 属性。但是现在它不能成为关键列

This created the problem that when Subject excess 128 characters, validation fails. So I just put a [MaxLength] attribute on it. But now it can't be a key column

我该怎么办？

推荐答案

如果使用的是 EF 6.1 ，则可以使用多列索引功能：

If You are using EF 6.1, you can use Multiple-Column Indexes feature:

public class Email
{
   [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
   public int Id { get; set; }
   [Index("IX_EmailUniqueness", 1, IsUnique = true)]
   public string Subject { get; set; }
   public string Body { get; set; }
   [Index("IX_EmailUniqueness", 2, IsUnique = true)]
   public string From { get; set; }
   [Index("IX_EmailUniqueness", 3, IsUnique = true)]
   public DateTime SentOn { get; set; }
   public List<string> To { get; set; }
}

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