LINQ to SQL add, delete and modify basic statements

Add class diagram

 

//创建LinqDB上下文实例 
DataClasses1DataContext db = new DataClasses1DataContext();

1. Add, first find the position to be added, use the object constructor to add the required content, and then use Add to add

stuinfo stu = db.stuinfo.FirstOrDefault(p => p.sid == 3); //找到sid为3的字段
stumark mark = new stumark()   //添加"李淳罡"的SQL成绩
{
    name = "SQL",
    score = "76"
};
stu.stumark.Add(mark);
db.SubmitChanges();      //最后必须写上提交更改 否则无效

2. Delete, delete all data using DeleteAllOnSubmit, delete a single piece of data using DeleteOnSubmit

            stuinfo stu = db.stuinfo.FirstOrDefault(p => p.sid == 2);
            if (stu != null)
            {

               db.stumark.DeleteAllOnSubmit(stu.stumark); //删除sid为2的学生的所有成绩
                db.SubmitChanges();

            };

3. To modify, use FirstOrDefault(p => p.sid == num); find the field that needs to be modified, and then directly modify the field

            stuinfo stu = db.stuinfo.FirstOrDefault(p => p.sid == 1);
            stu.sname = "Mr.张";
            stumark mark = db.stumark.FirstOrDefault(p => p.id == 1);  //修改id为1的成绩
            mark.score = "101";    //修改功能可以直接使用 无需其他操作
            db.SubmitChanges();