在实体对象中访问导航属性里的属性值出现异常“There is already an open DataReader associated with this Command which must be

在使用asp.net core+entity framework core时，出现上述错误，

解决方法：

修改数据库连接字符串：增加：MultipleActiveResultSets=true

"ConnectionStrings": {
    "Default": "Data Source=(localdb)\MSSQLLocalDB;Initial Catalog=AlexRBAC;Integrated Security=True;Connect Timeout=30;Encrypt=False;TrustServerCertificate=False;;MultipleActiveResultSets=true;ApplicationIntent=ReadWrite;MultiSubnetFailover=False"
  },

参考：

https://www.cnblogs.com/brown-birds/p/4062304.html