DBHelper 是 .NET ORM 类库，功能强大，基本可以实现零 SQL 语句，只支持 SQLSERVER 数据库。

初始化连接字符串

DBHelper.InitConnectionString(connectionString);

数据库表准备

--学生表
create table T_Student
(
    IdentityID int identity(1, 1) primary key,
    StuCode varchar(10) not null,
    StuName nvarchar(10) not null,
    StuAge datetime default(getdate()) not null,
	StuSex nvarchar(10) not null
)
insert into T_Student values('01' , '赵雷' , '1990-01-01' , '男');
insert into T_Student values('02' , '钱电' , '1990-12-21' , '男');
insert into T_Student values('03' , '孙风' , '1990-12-20' , '男');
insert into T_Student values('04' , '李云' , '1990-12-06' , '男');
insert into T_Student values('05' , '周梅' , '1991-12-01' , '女');
insert into T_Student values('06' , '吴兰' , '1992-01-01' , '女');
insert into T_Student values('07' , '郑竹' , '1989-01-01' , '女');
insert into T_Student values('09' , '张三' , '2017-12-20' , '女');
insert into T_Student values('10' , '李四' , '2017-12-25' , '女');
insert into T_Student values('11' , '李四' , '2012-06-06' , '女');
insert into T_Student values('12' , '赵六' , '2013-06-13' , '女');
insert into T_Student values('13' , '孙七' , '2014-06-01' , '女');
--课程表
create table T_Course
(
    IdentityID int identity(1, 1) primary key,
    CouCode varchar(10) not null,
    CouName nvarchar(10) not null,
    TeaCode varchar(10) not null
)
insert into T_Course values('01' , '语文' , '02');
insert into T_Course values('02' , '数学' , '01');
insert into T_Course values('03' , '英语' , '03');
--教师表
create table T_Teacher
(
    IdentityID int identity(1, 1) primary key,
    TeaCode varchar(10) not null,
    TeaName nvarchar(10) not null
)
insert into T_Teacher values('01' , '张三');
insert into T_Teacher values('02' , '李四');
insert into T_Teacher values('03' , '王五');
--成绩表
create table T_Score
(
    IdentityID int identity(1, 1) primary key,
    StuCode varchar(10) not null,
    CouCode varchar(10) not null,
    [Score] decimal(18, 1) default(0) not null
)
insert into T_Score values('01' , '01' , 80);
insert into T_Score values('01' , '02' , 90);
insert into T_Score values('01' , '03' , 99);
insert into T_Score values('02' , '01' , 70);
insert into T_Score values('02' , '02' , 60);
insert into T_Score values('02' , '03' , 80);
insert into T_Score values('03' , '01' , 80);
insert into T_Score values('03' , '02' , 80);
insert into T_Score values('03' , '03' , 80);
insert into T_Score values('04' , '01' , 50);
insert into T_Score values('04' , '02' , 30);
insert into T_Score values('04' , '03' , 20);
insert into T_Score values('05' , '01' , 76);
insert into T_Score values('05' , '02' , 87);
insert into T_Score values('06' , '01' , 31);
insert into T_Score values('06' , '03' , 34);
insert into T_Score values('07' , '02' , 89);
insert into T_Score values('07' , '03' , 98);
    

C# 实体模型准备

[DBT("T_Student")]
public class DTStudentModel
{
    [DBIncrementT]
    public int IdentityID { get; set; }
    public string StuCode { get; set; }
    public string StuName { get; set; }
    public DateTime StuAge { get; set; }
    public string StuSex { get; set; }
}
[DBT("DTCourseModel")]
public class DTCourseModel
{
    [DBIncrementT]
    public int IdentityID { get; set; }
    public string CouCode { get; set; }
    public string CouName { get; set; }
    public string TeaCode { get; set; }
}
[DBT("T_Teacher")]
public class DTTeacherModel
{
    [DBIncrementT]
    public int IdentityID { get; set; }
    public string TeaCode { get; set; }
    public string TeaName { get; set; }
}
[DBT("T_Score")]
public class DTScoreModel
{
    [DBIncrementT]
    public int IdentityID { get; set; }
    public string StuCode { get; set; }
    public string CouCode { get; set; }
    public decimal Score { get; set; }
}