实体框架按Enum值按字母顺序排序 [英] Entity Framework sort by Enum value alphabetically

问题描述

我有一个名为 Comment 的实体，该实体具有类型为 CommentType 的 enum 属性:

I have an entity called Comment, which has an enum property of type CommentType:

public class Comment
{
    public virtual Guid Id { get; private set; }
    public virtual CommentType CommentType { get; set; }
    // other prop removed for simplicity
}

public enum CommentType
{
    Comment,
    Correction,
    Improvement,
    BugFix,
    NewFeauture,
    Other 
}

我需要通过 CommentType 枚举的按字母顺序值从数据库中选择注释，例如

I need to select the comments from database by the alphabetically value of the CommentType enum, something like

_db.Comments.OrderBy(p => p.CommentType)

但是，Enum值被视为整数，并且排序不能按字母顺序正确地工作.

However, the Enum values are treated as integers, and the sort will not work alphabetically correctly.

是否可以将某些属性/元数据添加到Enum值中，以使它们按字母顺序正确排序?

Is there any way to add some attributes / metadata to the Enum values to make them sort correctly alphabetically?

一种解决方案是将整数值分配给枚举值，但是我已经有很多数据库记录需要更新.而且此解决方案不适用于新添加的枚举值.

One solution will be to assign the integer value to enum values, but i already have many database records that will need to be updated. And this solution is not good for new added enum values.

public enum CommentType
{
    Comment = 2,
    Correction = 3,
    Improvement = 4,
    BugFix = 1,
    NewFeauture = 5,
    Other = 6 
}

推荐答案

当前在数据库级别尚不知道您的枚举名称，因此我认为您有两种选择.

Currently your enum name is not known at database level so in my opinion you have two options.

1. 在服务器端使用值:

1. Use value on server side:

_db.Comments.ToList().OrderBy(p => p.CommentType.ToString())

在数据库端添加值:您应该创建将包含注释类型名称的表.然后，您可以在注释和commentTypeNames之间创建外键，并使用简单的选择:

Add value on database side: You should create table that will contain comment type names. And then you can create foreign key between comments and commentTypeNames and use simple select:

_db.Comments.OrderBy(c => c.CommentTypeNames.Name)

或者只是加入:

_db.Comments
    .Join(
        _db.CommentTypeNames, 
        c => c.CommentType, 
        ctn => ctn.CommentType,
        (c, ctn) => new { Comment = c, CommentName = ctn })
    .OrderBy(g => g.CommentName.Name)
    .Select(g => g.Comment);

也有计算列.我从来没有用过，所以我没有经验.也许您可以添加将由数据库上的CASE语句解析为字符串的列.但是，我不确定这将如何影响性能/可维护性.有关更多信息，您可以检查出于性能方面的考虑，我建议您采用选项2，最好在数据库中执行此类操作.

For performance reasons I would advise to take option 2, it's better to do such things in database.

我假设您首先使用代码，所以也许这篇文章对您有所帮助:

I assume that you are using code first so maybe this post will be helpful for you: EF5 Code First Enums and Lookup Tables

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