实体框架数据库优先，正确使用数据注释 [英] Entity Framework Database First with proper use of Data Anotations

问题描述

我有一个使用 EF 和Code First方法的项目，因此使用数据注释很简单。现在，我正在使用数据库优先，并且我发现使用数据注释更具体，因此我想知道实现它的正确步骤。

I have one project with EF and Code First approach and there using of Data Annotations was straight forward. Now I'm working with Database First and I see that using Data Annotations is more specific so I want to know the right steps to implement it.

我的项目的结构提供数据访问权限的是这样的：

The structure of my project that provides Data Access is this:

在 ModelExtensions 中是我创建的所有文件，用于将数据注释添加到 DbContextModel.tt 实体。

In ModelExtensions are all my files that I've created to add the Data Annotations to the DbContextModel.tt entities.

这是 ModelExtensions ：

using System;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.Text;

namespace DataAccess.ModelExtensions
{
    [MetadataType(typeof(MCS_ContentTypesMetaData))]
    public partial class MCS_ContentTypes : BaseEntity
    {

    }

    internal sealed class MCS_ContentTypesMetaData
    {
        [Required]
        [StringLength(10)]
        public string Name { get; set; }
    }
}

我在这里有几个问题。首先-名称空间。是这样的名称空间DataAccess.ModelExtensions 还是我必须删除 .ModelExtensions 部分。我最初在看一个使用DB的项目，那里的命名空间只是 DataAccess 不知道为什么需要它（如果需要）。另外-我是否需要向 DbContextModel.tt 实体添加一些其他引用？现在，我为此使用标准C＃类，然后将其重命名为：公共部分类MCS_ContentTypes：BaseEntity 。我是否必须使用一种特殊的方法来创建那些对象，以显式公开实体与该文件之间的连接？

I have several questions here. First - the namespace. Should it be like this namespace DataAccess.ModelExtensions or I have to remove the .ModelExtensions part. I was looking at a project using DB first and there the namespace was just DataAccess not sure why it is needed (if so). Also - Do I need to add some other references to the DbContextModel.tt entities? Now I use standard C# classes for this and then rename them to : public partial class MCS_ContentTypes : BaseEntity. Do I have to use a special approach for creating those to explicitly expose the connection between the entity and this file?

推荐答案

1）扩展模型的名称空间必须与EF自动生成的实体类的名称空间相同-如果 DbContextModel.tt 实体类的名称空间为 DataAccess ，则应将类的命名空间设置为 DataAccess 。

1) The namespace of your extension models must be the same as the namespace of EF auto-generated entity classes - If the namespace of DbContextModel.tt entity classes is DataAccess, you should set the namespace of your classes to DataAccess.

2）我没有完全解决您的问题，但是采用这种方法，实体类的名称和您的类必须相同。

2) I doesn't get your question completely, however in this approach, names of entity classes and your classes must be the same.

下面的示例说明了它应该是什么。假设EF为您生成了以下实体类：

The following example shows what it should be. Suppose that EF generates the following entity class for you:

namespace YourSolution
{
    using System;
    using System.Collections.Generic;

    public partial class News
    {
        public int ID { get; set; }
        public string Title { get; set; }        
    }
}

因此，您的部分类应如下所示：

So, your partial classes should be like the following:

namespace YourSolution
{
    [MetadataType(typeof(NewsAttribs))]
    public partial class News
    {
        // leave it empty.
    }

    public class NewsAttribs
    {            
        // Your attribs will come here.

        [Display(Name = "News title")]
        [Required(ErrorMessage = "Please enter the news title.")]
        public string Title { get; set; }

        // and other properties you want...
    }
}

因此，您不需要任何：BaseEntity 继承。

So, you doesn't need any : BaseEntity inheritance.

这篇关于实体框架数据库优先，正确使用数据注释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！