如何将通用配置应用于ef核心中的所有实体 [英] how to apply common configuration to all entities in ef core

问题描述

我的应用程序中有一个使用ef核心代码优先方法从基本实体派生的实体。

I have entities derived from a base entity in my application which uses ef core code-first approach.

基类

public abstract class BaseEntity<T> : IEntity<T>
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public T Id { get; set; }

    object IEntity.Id { get { return Id; } set { } }

    private DateTime? createdOn;
    [DataType(DataType.DateTime)]
    public DateTime CreatedOn { get => createdOn ?? DateTime.Now; set => createdOn = value; }

    [DataType(DataType.DateTime)]
    public DateTime? ModifiedOn { get; set; }

    public bool IsDeleted { get; set; }
    // Auto increment for all entities.
    public int OrderId { get; set; }
}

还有一个实体

public class UserEntity : BaseEntity<int>
{
    public string EmployeeId { get; set; }
    public string FullName { get; set; }
    public string Email { get; set; }
}

我可以应用 .ValueGeneratedOnAdd（）方法，每个实体的 OnModelCreating 中的属性 OrderId ，

I can apply the .ValueGeneratedOnAdd() method on property OrderId in OnModelCreating for each entity however, is there a way to apply a general rule for all entities without repeatig yourself?

推荐答案

由于缺少自定义约定，您可以在所有实体上应用通用规则而不自己重复吗？使用典型的 modelBuilder.Model.GetEntityTypes（）循环，标识目标实体类型并调用通用配置。

With the lack of custom conventions, you could use the typical modelBuilder.Model.GetEntityTypes() loop, identify the target entity types and invoke common configuration.

由于基本的 generic 类，您的情况下的识别有点复杂，但可以通过迭代 Type.BaseType 并检查<$ c $来实现c> BaseEntity<> 。找到它之后，您可以检索稍后需要的通用参数 T 。

Identification in your case is a bit complicated because of the base generic class, but doable by iterating down Type.BaseType and check for BaseEntity<>. Once you find it, you can retrieve the generic argument T which you'll need later.

不想使用实现 IEnityTypeConfiguration< TEntity> 的 generic 类，那么该想法是将实现放入 generic约束这样的方法

If you don't want to use generic class implementing IEnityTypeConfiguration<TEntity>, then the idea is to put the implementation in generic constrained method like this

static void Configure<TEntity, T>(ModelBuilder modelBuilder)
    where TEntity : BaseEntity<T>
{
    modelBuilder.Entity<TEntity>(builder =>
    {
        builder.Property(e => e.OrderId).ValueGeneratedOnAdd();
    });
}

传递实际实体类型 TEntity 到 modelBuilder.Enity 方法非常关键，因为否则，EF Core将把您传递的任何内容视为实体类型并配置TPH继承。

Passing the actual entity type TEntity to modelBuilder.Enity method is crucial, because otherwise EF Core will consider whatever you pass to be an entity type and configure TPH inheritance.

调用该方法需要反思-使用 MakeGenericMethod 然后再 Invoke 。

Calling the method requires reflection - finding the generic method definition, using MakeGenericMethod and then Invoke.

以下是封装在静态类中的所有内容：

Here is all that encapsulated in a static class:

public static class BaseEntityConfiguration
{
    static void Configure<TEntity, T>(ModelBuilder modelBuilder)
        where TEntity : BaseEntity<T>
    {
        modelBuilder.Entity<TEntity>(builder =>
        {
            builder.Property(e => e.OrderId).ValueGeneratedOnAdd();
        });
    }

    public static ModelBuilder ApplyBaseEntityConfiguration(this ModelBuilder modelBuilder)
    {
        var method = typeof(BaseEntityConfiguration).GetTypeInfo().DeclaredMethods
            .Single(m => m.Name == nameof(Configure));
        foreach (var entityType in modelBuilder.Model.GetEntityTypes())
        {
            if (entityType.ClrType.IsBaseEntity(out var T))
                method.MakeGenericMethod(entityType.ClrType, T).Invoke(null, new[] { modelBuilder });
        }
        return modelBuilder;
    }

    static bool IsBaseEntity(this Type type, out Type T)
    {
        for (var baseType = type.BaseType; baseType != null; baseType = baseType.BaseType)
        {
            if (baseType.IsGenericType && baseType.GetGenericTypeDefinition() == typeof(BaseEntity<>))
            {
                T = baseType.GetGenericArguments()[0];
                return true;
            }
        }
        T = null;
        return false;
    }
}

现在您所需要的只是从内部调用它 OnModelCreating 覆盖：

Now all you need is to call it from inside your OnModelCreating override:

modelBuilder.ApplyBaseEntityConfiguration();

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