.net 6 efcore一个model映射到多张表(非使用IEntityTypeConfiguration)

现在有两张表，结构一模一样，我又不想创建两个一模一样的model，就想一个model映射到两张表

废话不多说直接上代码

安装依赖包
创建model

csharp 复制代码

namespace oneModelMultiTable.Model
{
    public class Test
    {
        public int id { get; set; }

        public string name { get; set; }

        public string tablename { get; set; }
    }
}

创建DBContext
我们需要使用tablename 动态指定表名，因此需要在DBContext中添加这个属性

csharp 复制代码

namespace oneModelMultiTable
{
    public class DBHelper:DbContext
    {
        public DbSet<Test> testConfigs { get; set; }

        public string tablename { get; set; }
        public DBHelper(DbContextOptions<DBHelper> options):base(options)
        {

        }
        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {

            modelBuilder.Entity<Test>(b =>
            {
                b.ToTable(tablename);
                b.HasKey(p => p.id);
            });

            base.OnModelCreating(modelBuilder);

            //modelBuilder.ApplyConfigurationsFromAssembly(this.GetType().Assembly);
        }
    }
}

创建DynamicModelCacheKeyFactory 继承IModelCacheKeyFactory

csharp 复制代码

using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
namespace oneModelMultiTable
{
    public class DynamicModelCacheKeyFactory : IModelCacheKeyFactory
    {

        public object Create(DbContext context, bool designTime)
        {
            object p = context is DBHelper dynamicContext
                ? (context.GetType(), dynamicContext.tablename)
                : (object)context.GetType();
            return p;
        }
    }
}

依赖注入

csharp 复制代码

builder.Services.AddDbContext<DBHelper>(options =>
{
    options.UseNpgsql(@"Host=192.168.214.133;Port=32222;Database=postgresdb;Username=postgresadmin;Password=admin123")
    .ReplaceService<IModelCacheKeyFactory, DynamicModelCacheKeyFactory>();
});

创建controller

csharp 复制代码

using Microsoft.AspNetCore.Mvc;
using oneModelMultiTable.Model;

// For more information on enabling Web API for empty projects, visit https://go.microsoft.com/fwlink/?LinkID=397860

namespace oneModelMultiTable.Controllers
{
    [Route("api/[controller]/[action]")]
    [ApiController]
    public class TestController : ControllerBase
    {
        public readonly DBHelper dBHelper;

        public TestController(DBHelper _DBHelper)
        {
            dBHelper = _DBHelper;
        }

        // GET: api/<TestController>
        [HttpGet]
        public List<Test> Get(string tablename)
        {
            dBHelper.tablename = tablename;
            return dBHelper.testConfigs.ToList();
        }
    }
}

原理

你可能想通过ToTable()方法来更改表名，但是我们如何在OnModelCreating方法中更改表名呢?当EF构建模型时，它只运行OnModelCreating一次。

对于这个场景，我们需要通过使用IModelCacheKeyFactory 来更改默认映射，它允许我们连接到模型缓存机制，以便EF可以根据其属性创建不同的模型。

EF使用IModelCacheKeyFactory为模型生成缓存键。

https://yanxiaodi.medium.com/mapping-the-model-to-multiple-tables-with-entityframework-core-b46bdeed8661

https://medium.com/@pawel.gerr/entity-framework-core-changing-database-schema-at-runtime-dcf1211768c6

https://github.com/xdqt/asp.net-core/tree/master/oneModelMultiTable