如何存储 IEnumerable<string> 的属性?在 Cosmos 表中，使用 EF Core 3.1 [英] How do I store a property of IEnumerable&lt;string&gt; in a Cosmos table, with EF Core 3.1

问题描述

我的项目使用 EF Core 3.1，并将 Azure Cosmos 作为数据库.

My project is using EF Core 3.1, and targeting Azure Cosmos as the database.

我有一个这样的实体:

public class MyEntity
{
    public IEnumerable<string> Names {get;set;}
    ... other fields
}

我希望以这样的 Cosmos 文档结尾:

That I would like to end up in a Cosmos document like this:

{
    "Names": ["Name1", "Name2"]
}

使用实体 (IEnumerable) 我得到错误:

With the entity as is (IEnumerable<string>) I get the error:

无法映射属性MyEntity.Names"，因为它属于IEnumerable"类型，它不是受支持的原始类型或有效的实体类型.

The property 'MyEntity.Names' could not be mapped, because it is of type 'IEnumerable' which is not a supported primitive type or a valid entity type.

如果我将实体更改为:

public class NameEntity
{
    public string Name {get;set;}
}
public class MyEntity
{
    public IEnumerable<NameEntity> Names {get;set;}
    ... other fields
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<MyEntity>(e =>
    {
        e.OwnsMany(p => p.Identifiers);
    });
}

文档如下所示:

{
    "Id": "XXXXXX",
    "Names:" [
       {},
       {}
    ],
}

所以我改变了 OnModelCreating:

So I change the OnModelCreating:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    modelBuilder.Entity<MyEntity>(e =>
    {
        e.OwnsMany(p => p.Identifiers, o=> o.HasKey(k=>k.Name));
    });
}

然后我得到:

{
  "Names": [
    {
        "Name": "<string1>",
        "Id": "XXXX"
    },
    {
        "Identifier": "<string2>",
        "Id": "XXXX"
    }
]}

我也研究过值转换器，但我认为它更多地用于在类型之间转换属性值，而不是将实体转换为字符串.

I've also looked at value converters, but I think that is more for converting property values between types, rather than converting an entity to a string.

任何帮助将不胜感激.

推荐答案

这里有一个和你类似的问题:实体框架 - 代码优先 - 无法存储列表

Here is a similar question to yours : Entity Framework - Code First - Can't Store List<String>

目前，无法存储原始类型列表(包括字符串).

Currently, it's not possible to store a list of primitive type (string included).

最好的办法是将列表作为字符串存储在数据库中，并在获取它时将其转换回列表.

Your best bet would be to store the list as a string in your database, and when you fetch it you transform it back to a list.

正如上面的链接所解释的那样，您可以在 OnModelCreating 方法中进行:

As the link above explained it, you can do in your OnModelCreating method :

modelBuilder.Entity<YourEntity>()
        .Property(e => e.Strings)
        .HasConversion(
            v => string.Join(',', v),
            v => v.Split(',', StringSplitOptions.RemoveEmptyEntries));

这篇关于如何存储 IEnumerable<string> 的属性?在 Cosmos 表中，使用 EF Core 3.1的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！