Question

我有以下课程。我有一个Description类的对象var。我想使用Linq to Sql或Lambda表达式选择与var对象中提供的客户端相关的余额。如何连接这些表以从帐户表中获取余额？

public class Description
    {
        public int DescriptionID { get; set; }

       // Attributes

        public int ClientID { get; set; }

        [ForeignKey("ClientID")]
        public virtual Client Client { get; set; }


    }

public class Client
    {
        public int ClientID { get; set; }

       // Attributes

        public int UserID { get; set; }

        [ForeignKey("UserID")]
        public virtual User User { get; set; }

    }

 public class User
    {
        public int UserID { get; set; }

       // Attributes

     }

 public class Account
    {

        public int AccountID { get; set; }

        [Required, Column("Balance"), Display(Name = "Account Balance")]
        public double Balance { get; set; }


        public int UserID { get; set; }

        [ForeignKey("UserID")]
        public virtual User User { get; set; }

    }

Answer 1

你可以试试这个：

var balance = (from a in context.Accounts
               join c in context.Clients on a.UserID equals c.UserID
               where c.ClientID == yourDescriptionObject.ClientID
               select a.Balance)
              .SingleOrDefault();

或 - 如果您只有DescriptionID：

var balance = (from a in context.Accounts
               join c in context.Clients on a.UserID equals c.UserID
               join d in context.Descriptions on c.ClientID equals d.ClientID
               where d.DescriptionID == yourDescriptionID
               select a.Balance)
              .SingleOrDefault();

（或FirstOrDefault()或ToList()或Sum()？因为您的模型会允许客户/说明与多个帐户相关...）

如何加入多个表？

1 个答案: