static void Main(string[] args)
{
////获取数据源
//int[] numbers = new int[]{ 1, 2, 5, 7, 9, 11, 12, 14 };
////写LINQ语句
//var obj = from a in numbers where a % 2 == 0 select a;
//foreach (var item in obj)
//{
// Console.WriteLine(item);
//}
using (ncovDBEntities db = new ncovDBEntities())
{
//1、查询学生信息
Console.WriteLine("---------第一题------");
var obj1 = from stu in db.tbStu select stu;
foreach (var item in obj1)
{
Console.WriteLine("编号:{0},姓名:{1},地址：{2}", item.stuID, item.stuName, item.stuAddress);
}
//2、查询在湖南长沙的学生信息
Console.WriteLine("---------第二题------");
var obj2 = db.tbStu.Where(p => p.stuAddress == "湖南长沙");
//var obj2 = from stu in db.tbStu where stu.stuAddress=="湖南常德" select stu;
foreach (var item in obj2)
{
Console.WriteLine("编号:{0},姓名:{1},地址：{2}", item.stuID, item.stuName, item.stuAddress);
}
//3、按学生所在地址分组查询学生信息
Console.WriteLine("---------第三题------");
var obj3 = from stu in db.tbStu group stu by stu.stuAddress;
foreach (var item in obj3)
{
Console.WriteLine("学生所在地区：{0}", item.Key);
var m = from stu in db.tbStu where item.Key == stu.stuAddress select stu;
foreach (var b in m)
{
Console.WriteLine("编号:{0},姓名:{1}", b.stuID, b.stuName);
}
//Console.WriteLine("地址：{0}，人数；{1}",item.Key,item.Count());
}
//4、查询不同所在地的学生数量
Console.WriteLine("---------第四题------");
var obj4 = from stu in db.tbStu group stu by stu.stuAddress into g select new { GroupKey = g.Key, Person = g.Count() };
foreach (var item in obj4)
{
Console.WriteLine("地址：{0}，人数；{1}", item.GroupKey, item.Person);
}
//5、查询学生姓名、学生所在地址，并通过姓名降序排列
Console.WriteLine("---------第五题------");
var obj5 = from stu in db.tbStu orderby stu.stuName ascending select stu;
foreach (var item in obj5)
{
Console.WriteLine("编号:{0},姓名:{1},地址：{2}", item.stuID, item.stuName, item.stuAddress);
}
//6、联合表查询，学生的上报填表信息
var obj6 = from a in db.tbStu join b in db.tbDetail on a.stuID equals b.stuID select new { value1 = a, value2 = b };
foreach (var item in obj6)
{
Console.WriteLine("姓名：{0}，上报时间：{1}，是否咳嗽：{2}，是否发烧：{3}", item.value1.stuName, item.value2.fillTime, item.value2.isCough, item.value2.isFever);
}
}
}
static void Main(string[] args)
{
using (ncovDBEntities db = new ncovDBEntities())
{
Console.WriteLine("-------TOdictionary--key value键值对----");
var obj = db.tbStu.ToDictionary(p => p.stuID);
Console.WriteLine("-------直接循环");
foreach (var item in obj)
{
Console.WriteLine("{0},{1},{2}", item.Value.stuID, item.Value.stuName, item.Value.stuAddress);
}
Console.WriteLine("-------TolookUp()---key value键值对-1对多----");
var obj2 = db.tbStu.ToLookup(p => p.stuID);
foreach (var item in obj2)
{
Console.WriteLine(item.Key);
foreach (var item1 in item)
{
Console.WriteLine("{0},{1},{2}", item1.stuID, item1.stuName, item1.stuAddress);
}
}
//Console.WriteLine("-------循环Values");
//foreach (var item in obj.Values)
//{
// Console.WriteLine("{0},{1},{2}", item.stuID, item.stuName, item.stuAddress);
//}
//Console.WriteLine("-------通过Keys循环");
//foreach (var item in obj.Keys)
//{
// Console.WriteLine("{0},{1},{2}", obj[item].stuID, obj[item].stuName, obj[item].stuAddress);
//}
}
using (ncovDBEntities db = new ncovDBEntities())
{
Console.WriteLine("-------TOdictionary--key value键值对----");
Console.WriteLine("-------将具体的某项值作为dictionary的value值----");
//var obj = db.tbStu.ToDictionary(p => p.stuID, k => k.stuName);
//foreach (var item in obj)
//{
// Console.WriteLine(item);
//}
//Console.WriteLine("-------将自定义对象作为dictionary的value值----");
//var obj = db.tbStu.ToDictionary(p => p.stuID, k => new { name = k, address = k.stuAddress });
//foreach (var item in obj.Values)
//{
// Console.WriteLine(item.name+item.address);
//}
}
//添加
//创建实体
//tbTea tea = new tbTea()
//{
// TeaName = "胡瑶",
//};
////添加
//using (ncovDBEntities db = new ncovDBEntities())
//{
// tbStu stu = new tbStu()
// {
// stuID = "201817380120",
// stuName = "杨磊",
// stuAddress = "湖南常德"
// };
// //在上下文类学生实体集合中添加学生信息
// db.tbStu.Add(stu);
// //保存
// db.SaveChanges();
//}
//Console.WriteLine("添加成功");
//Console.WriteLine();
//Console.WriteLine("学生信息如下：");
//using (ncovDBEntities db = new ncovDBEntities())
//{
// List<tbStu> list = db.tbStu.ToList();
// foreach (var item in list)
// {
// Console.WriteLine("学生的ID是：{0},学生的姓名是：{1},学生的地址：{2}", item.stuID, item.stuName, item.stuAddress);
// }
//}
//Console.WriteLine();
//根据主键去查询
//using (ncovDBEntities db = new ncovDBEntities())
//{
// var stu1 = db.tbStu.Find("201817380120");
// Console.WriteLine("学生的姓名是："+ stu1.stuName);
// Console.WriteLine("学生的ID是是：" + stu1.stuID);
// Console.WriteLine("学生的地址是：" + stu1.stuAddress);
//}
//修改方法一
//using (ncovDBEntities db = new ncovDBEntities())
//{
// var stu = db.tbStu.Find("201817380120");
// stu.stuAddress = "湖南长沙";
// db.SaveChanges();
//}
//修改方法二
//var stu = db.tbStu.Find("201817380120");
//stu.stuAddress = "湖南长沙";
//db.Entry(stu).State = System.Data.Entity.EntityState.Modified;
//db.SaveChanges();
//Console.WriteLine("修改成功");
//删除---
//var stu = db.tbStu.Find("201817380120");
//db.tbStu.Remove(stu);
//db.SaveChanges();
//Console.WriteLine("删除成功");
// var stu = db.tbStu.Find("201817380120");
// //db.tbStu.Remove(stu);
// db.Entry(stu).State = System.Data.Entity.EntityState.Deleted;
// db.SaveChanges();
// Console.WriteLine("删除成功");
}
