GetEntityTypes：使用.Property< TEntity>的通用版本来配置实体属性。在EF Core中

问题描述

在我的EF核心项目中，我有一些实体是从基类DBEntity继承的：

In my EF core project I have a few entities that inherit from a base class DBEntity:

public abstract class DBEntity
{
    public int Id { get; set; }

    public DateTime CreatedOn { get; set; }

    public DateTime UpdatedOn { get; set; }

    public EntityStatus EntityStatus { get; set; }
}

我想为每个继承的实体设置一些默认值的特定属性来自DBEntity。目前，我正在使用以下代码：

I want to set some specific properties with default value for every entity that inherits from DBEntity. Currently I'm using this code:

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {

        var entities = modelBuilder.Model
            .GetEntityTypes()
            .Where(w => w.ClrType.IsSubclassOf(typeof(DBEntity)))
            .Select(p => modelBuilder.Entity(p.ClrType));

        foreach (var entity in entities)
        {

            entity
                .Property("CreatedOn")
                .HasDefaultValueSql("GETDATE()");

            entity
                .Property("UpdatedOn")
                .HasComputedColumnSql("GETDATE()");

            entity
                .Property("EntityStatus")
                .HasDefaultValue(EntityStatus.Created);

        }
    }

这很好，但我不想要使用字符串常量来指定属性名称（对于重构等不利）。

This works fine but I don't want to specify property names using string constants (bad for refactoring etc.).

有没有一种方法可以遍历从DBEntity继承的实体并使用属性表达式来配​​置默认值，例如：

Is there a way to loop through entities that inherit from DBEntity and use property expression to configure default values like this:

foreach (var entity in entities)
{
    entity
      .Property(k => k.CreatedOn)
      .HasDefaultValueSql("GETDATE()");

// ....

}

重要约束：我无法直接调用modelBuilder.Entity（）。Property（k => k.CreatedOn），因为它会弄乱所有表。

Important constraint: I cannot directly call modelBuilder.Entity().Property(k => k.CreatedOn) because it will mess up all tables.

推荐答案

正如注释中指出的，您可以简单地将字符串常量替换为 nameof（DBEntity.CreatedOn）等。

As pointed out in the comments, you can simply replace the string constants with nameof(DBEntity.CreatedOn) etc.

但是，如果要使用类型化访问器，则可以将基本实体配置代码移至 generic 方法（generic参数为

But if you want to work with typed accessors, you can move the base entity configuration code to a generic method (with the generic argument being the actual entity type) and call it via reflection.

例如，将以下内容添加到您的 DbContext 派生类中：

For instance, add the following to your DbContext derived class:

static void ConfigureDBEntity<TEntity>(ModelBuilder modelBuilder)
    where TEntity : DBEntity
{
    var entity = modelBuilder.Entity<TEntity>();

    entity
        .Property(e => e.CreatedOn)
        .HasDefaultValueSql("GETDATE()");

    entity
        .Property(e => e.UpdatedOn)
        .HasComputedColumnSql("GETDATE()");

    entity
        .Property(e => e.EntityStatus)
        .HasDefaultValue(EntityStatus.Created);

}

然后使用类似这样的东西：

and then use something like this:

var entityTypes = modelBuilder.Model
        .GetEntityTypes()
        .Where(t => t.ClrType.IsSubclassOf(typeof(DBEntity)));

var configureMethod = GetType().GetTypeInfo().DeclaredMethods.Single(m => m.Name == nameof(ConfigureDBEntity));
var args = new object[] { modelBuilder };
foreach (var entityType in entityTypes)
    configureMethod.MakeGenericMethod(entityType.ClrType).Invoke(null, args);

这篇关于GetEntityTypes：使用.Property< TEntity>的通用版本来配置实体属性。在EF Core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！