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LINQ表间关系查询的方法是什么

发表于：2025-01-19 作者：千家信息网编辑

千家信息网最后更新 2025年01月19日，本篇内容主要讲解"LINQ表间关系查询的方法是什么"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"LINQ表间关系查询的方法是什么"吧!LINQ表间关系查询

千家信息网最后更新 2025年01月19日LINQ表间关系查询的方法是什么

本篇内容主要讲解"LINQ表间关系查询的方法是什么"，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习"LINQ表间关系查询的方法是什么"吧!

LINQ表间关系查询

EnitySet类型为一对多关系中的"多"方的结果提供集合。与[Association]属性结合使用来定义并表示一个关系。OtherKey特性，指定在关联的另一端上作为键值的、目标实体类的一个或多个成员。

EnitityRef与EntitySet相反，用于一对多关系中的"一"方。与[Association]属性结合使用来定义并表示一个关系。ThisKey表示关联的此端上的键值的此实体类成员。

LINQ表间关系查询-EntitySet

//Student实体类
[Table(Name = "Student")]
public class Student
{
[Column(IsPrimaryKey = true, DbType = "int")]
public int ID;
[Column(DbType = "varchar(50)")]
public string StuName;
[Column(DbType = "bit")]
public bool Sex;
[Column(DbType = "int")]
public int Age;
private EntitySet _scores;
[Association(Storage = "_scores", OtherKey = "StudentID")]
public EntitySet Score
{
get { return this._scores; }
set { this._scores.Assign(value); }
}
}
//Scores实体类
[Table(Name = "Score")]
public class Score
{
[Column(IsPrimaryKey = true, DbType = "int")]
public int ID;
[Column(DbType = "int")]
public int StudentID;
[Column(DbType = "float")]
public float Math;
[Column(DbType = "float")]public float Chinese;
[Column(DbType = "float")]
public float English;
[Column(DbType = "Datetime")]
public DateTime Times;
}
public class TestDB : DataContext
{
public TestDB(string constr)
: base(constr)
{ }
public Table Student;
public Table Scores;
}
static string constr = "server=.;database=test;uid=sa;pwd=sa;";
static void Main()
{
//调用存储课程
TestDB Test = new TestDB(constr);
IQueryable s = from stu in Test.Student
select stu;
foreach (var v in s)
{
Console.WriteLine(v.StuName);
foreach (var o in v.Score)
{
Console.WriteLine(" 编号：{0}，学生姓名：{1}，学生年龄：{2}，
语文成绩：{3}，考试时间：{4}", v.ID, v.StuName, v.Age,
o.Chinese, o.Times.ToString("yyyy年MM月dd日"));
}
}
}

表间关系查询-EntytyRef

//Student实体类
[Table(Name = "Student")]
public class Student
{
[Column(IsPrimaryKey = true, DbType = "int")]
public int ID;
[Column(DbType = "varchar(50)")]
public string StuName;
[Column(DbType = "bit")]
public bool Sex;
[Column(DbType = "int")]
public int Age;
}
//Scores实体类
[Table(Name = "Score")]
public class Score
{
[Column(IsPrimaryKey = true, DbType = "int")]
public int ID
[Column(DbType = "int")]
public int StudentID;
[Column(DbType = "float")]
public float Math;
[Column(DbType = "float")]
public float Chinese;
[Column(DbType = "float")]
public float English;
[Column(DbType = "Datetime")]
public DateTime Times;
private EntityRef _Student;
[Association(Storage = "_Student", ThisKey = "StudentID")]
public Student Student
{
get { return this._Student.Entity; }
set { this._Student.Entity = value; }
}
}
public class TestDB : DataContext
{
public TestDB(string constr)
: base(constr)
{ }
public Table Student;
public Table Scores;
}
static string constr = "server=.;database=test;uid=sa;pwd=sa;";
static void Main()
{
//调用存储课程
TestDB Test = new TestDB(constr);
var query = from sco in Test.Scores
select sco;
foreach (var s in query)
{
Console.WriteLine(" 编号：{0}，学生姓名：{1}，学生年龄：{2}，
语文成绩：{3}，考试时间：{4}", s.StudentID ,s.Student.StuName,
s.Student.Age,s.Chinese, s.Times.ToString("yyyy年MM月dd日"));
}
}