Core ef连接数据库

1：添加nuget Microsoft.EntityframeworkCore.SqlServer

2：在appsettings.json中添加数据库连接语句 

"ConnectionStrings": {
    "SqlServerConnection": "Data Source = Data Source;Initial Catalog = nitial Catalog;User Id = User Id;Password = Password;"
  }

3：定义DBContext文件

    public class SDKDalDBContext: DbContext
    {
        public SDKDalDBContext(DbContextOptions options) :base(options)
        {

        }

}

4：注册中间件，在Startup.cs 方法 ConfigureServices 中添加

services.AddDbContextPool(options => options.UseSqlServer(_configuration.GetConnectionString("SqlServerConnection")));

用构造函数的方法注入IConfiguration 以便读取配置文件

public Startup(IConfiguration configuration)
{
       _configuration = configuration;
}