如何使用EF 6在另一个表中添加外键的列描述?

问题描述

请参阅上一篇文章:

我已经成功实现了用户阿卜杜拉(abdullah)提出的修改后的解决方案，但是我遇到了以下异常:

I have successfully implemented the modified solution proposed by user Abdullah but I have encountered the exception below:

示例代码如下:

public class School
{
    public School()
    {
        Students = new HashSet<Student>();
    }
    
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Key]
    public Guid Id { get; set; }

    [Description("Some Text")]
    public string Description { get; set; }
    
    [Description("Some text")]
    public ICollection<Student> Students{ get; set; }
}

我从异常消息中了解到，没有为学生生成任何列.检查数据库，显示Student表的列SchoolId为FK.

I understand from the exception message, there is no column generated for Students. Checking the DB shows that the Student table have the column SchoolId as FK.

所以这里的问题是:当EF在另一个表中生成FK列时，如何添加/更新FK描述?

So the question here is: how do I go about adding/updating the FK description when EF generates the FK column in another table?

推荐答案

尽管他没有回答我的问题，但我要感谢 Raihan使我有了再次检查如何声明外键的想法.:)

Although he did not answer my question, I have to thank Raihan for giving me the idea to check again on how Foreign Keys can be declared. :)

基于实体框架教程，可以通过3种方式声明外键:

Based on Entity Framework Tutorial, a foreign key can be declared 3 ways:

1. 从属实体中的外键标量属性上的[ForeignKey(NavigationPropertyName)].
2. 从属实体中相关参考导航属性上的[ForeignKey(ForeignKeyPropertyName)].
3. 主体实体中导航属性上的[ForeignKey(ForeignKeyPropertyName)].

还引用在Entity Framework Tutorial网站上如何声明一对多关系部分，我们可以看到我在问题中描述的方法是公约2.

Also referencing to how a one-many relationship can be declared section in Entity Framework Tutorial website, we can see that the method which I had described in my question is Convention 2.

为了使Raihan用户的建议生效，我将需要将多个声明更改为Convention 3，这是在 School 和 Student 类.如下所示:

In order for User Raihan's suggestion to work, I will need to change the one-many declaration to Convention 3, which is to declare a navigational properties at both the School and Student classes. Like below:

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; }
    public School School { get; set; }
}

public class School
{
    public int GradeID { get; set; }
    public string GradeName { get; set; }
    public string Section { get; set; }

    public ICollection<Student> Student { get; set; }
}

请参考同一网站中的外键声明示例，如下所示，需要对 Student 类进行进一步修改，以使(Description)属性起作用:

Referencing the foreign key declaration sample in the same website, the Student class needs to be further modified as shown below in order for the (Description) attribute to work:

public class Student
{
    [Description("Id of Student")]
    [Key]
    public int Id { get; set; }
    [Description("Name of Student")]
    public string Name { get; set; }

    [Description("Some Description")]
    public int SchoolId {get; set;}
    public School School { get; set; }
}

我仍在寻找一种获取列说明的较短方法，因此，如果您认为您的解决方案比我的解决方案更优雅，请回复.:)

I am still looking for a shorter way to get the column description in so please do reply if you think your solution is more elegant than mine.. :)

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