我如何实现一个简单的“复杂类型"?在 Entity Framework Core 2/C# 中? [英] How do I implement a simple "complex type" in Entity Framework Core 2/C#?

问题描述

我第一次使用 Entity Framework 和 .Net Core 2.0(我对 C# 也很陌生，但我从版本 1 开始就一直在使用传统的 .Net Framework 和 VB ......所以我我不是 .Net 开发的新手)，而且我在创建数据库时遇到了问题.

I'm using Entity Framework and .Net Core 2.0 for the first time (I'm also pretty new to C#, but I've been using the traditional .Net Framework & VB since version 1... so I'm no newbie to .Net development), and I've already run into a problem creating my database.

以这个简单的场景为例:我想存储一些关于一些电动泵的信息.其中两个属性是最小/最大类型范围，因此我将它们实现为一个简单的类，因此:

Take this simple scenario: I want to store some information about some electric pumps. Two of the properties are a min/max type range, so I've implemented these as a simple class, thus:

public class Pump
{
    [Key]
    public int pumpId { get; set; }
    public string pumpName { get; set; }
    public int pumpControlChannel { get; set; }
    public MinMax normalCurrent { get; set; }
    public MinMax normalFlowRate { get; set; }
}

[ComplexType]
public class MinMax
{
    public int min { get; set; }
    public int max { get; set; }
}

如您所见，我尝试了 [ComplexType] 装饰器，但无济于事.

As you can see, I've tried the [ComplexType] decorator, to no avail.

无论如何，现在创建一个简单的 DBContext 类来管理我的 Pumps 类.我正在使用 Sqlite:

Anyway, now create a dead simple DBContext class to manage my Pumps class. I'm using Sqlite:

public class EFDB : DbContext
{
    public DbSet<Pump> pumps { get; private set; }

    private static DbContextOptions GetOptions(string connectionString)
    {
        var modelBuilder = new DbContextOptionsBuilder();
        return modelBuilder.UseSqlite(connectionString).Options;
    }

    public EFDB(string connectionString) : base(GetOptions(connectionString)) { }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        try
        {
            // modelBuilder.ComplexType<MinMax>();      // ComplexType not recognised
            base.OnModelCreating(modelBuilder);
        }
        catch (Exception ex)
        {
            System.Diagnostics.Debugger.Break();
        }
    }

}

最后一个简单的静态类来调用它(我将它嵌入到一个更大的程序中...要复制这个问题，你可以将代码行粘贴到 program.cs 中):

and lastly a simple static class to call it (I embeded it in a bigger program... to duplicate this problem you could just stick the code lines into program.cs):

public static class TryMe
{
    public static void MakeMeFail()
    {
        using (var db = new EFDB("FileName=C:\temp\test_effail.db"))
        {
            try
            {
                db.Database.EnsureCreated();
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debugger.Break();   // If we hit this line, it fell over
            }
        }
        System.Diagnostics.Debugger.Break();   // If we hit this line, it worked.
    }
}

只需调用TryMe.MakeMeFail()，代码在db.Database.EnsureCreated()处失败.

Just call TryMe.MakeMeFail(), the code fails at db.Database.EnsureCreated().

从我读过的所有内容来看，[ComplexType] 应该做我想做的事……但事实并非如此.我也找不到 modelBuilder.ComplexType 任何地方.

From everything I've read, [ComplexType] should do what I want... but it Just Doesn't. Nor can I find modelBuilder.ComplexType<T> anywhere.

这可能只是我遗漏的图书馆参考资料...?上面的代码使用了以下内容:

It may just be a library reference I'm missing...? The above code uses the following:

using System;
using Microsoft.EntityFrameworkCore;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

但是，我在任何地方都找不到任何文档/示例显示哪些库需要引用！

However, NONE of the documentation/examples I can find anywhere show which libraries need referencing!

提前致谢.

[PS:向已经看到这个问题的人道歉，我使用的是 EF Core 2.0，而不是 EF6]

[PS: Apologies to those who already saw this question, I'm using EF Core 2.0, NOT EF6]

推荐答案

典型的...总是这样，不是吗?发帖 5 分钟后，您会发现自己问题的答案....

Typical... it's always the way, isn't it? 5 minutes after posting, you discover the answer to your own question....

在这种情况下，答案可以在这里找到:

The answer, in this case, can be found here:

https://docs.microsoft.com/en-us/ef/core/modeling/owned-entities

EF Core 将这种实体称为拥有的"实体，而不是复杂类型".

EF Core calls this sort of entity an "owned" entity, rather than a "complex type".

只需将这些行添加到OnModelCreating"即可解决问题:

Simply adding these lines to `OnModelCreating' fixed the issue:

modelBuilder.Entity<Pump>().OwnsOne(p => p.normalCurrent);
modelBuilder.Entity<Pump>().OwnsOne(p => p.normalFlowRate);

数据库现在创建了(我认为是正确的，我还没有验证).

The database now creates (correctly, I think, I haven't verified that yet).

这篇关于我如何实现一个简单的“复杂类型"?在 Entity Framework Core 2/C# 中?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！