Unable to create an object of type 'SchoolContext'. Add an implementation of

Unable to create an object of type 'SchoolContext'. Add an implementation of

 net  core 新搭建基架或操作数据库迁移时报错：

Unable to create an object of type 'SchoolContext'. Add an implementation of 'IDesignTimeDbContextFactory<SchoolContext>' to the project, or see /?linkid=851728 for additional patterns supported at design time.

查找相关资料，解决办法如下：

在Data文件夹，创建一个名称为：SchoolContextFactory 的类，类代码如下：

namespace ContosoUniversity.Data
{
    public class SchoolContextFactory:IDesignTimeDbContextFactory<SchoolContext>
    {
       // IConfiguration Configuration { get; } //使用Configuration 获取不到GetConnectionString("SchoolContext")。不能用
        public SchoolContext CreateDbContext(string[] args)
        {
            var optionsBuilder = new DbContextOptionsBuilder<SchoolContext>();
            //   optionsBuilder.UseSqlServer(Configuration.GetConnectionString("SchoolContext"));
            optionsBuilder.UseSqlServer("Server = (localdb)\mssqllocaldb; Database = SchoolContext; Trusted_Connection = True; MultipleActiveResultSets = true");
            return new SchoolContext(optionsBuilder.Options);
        }

    }
}

注意： 红字内容。